Photonics Glossary and List of Formula Symbols
On this page, you first find the glossary of photonics terms, which is based on the definitions in the Encyclopedia articles. These have been carefully worked out, such that they can be considered as authoritative.
Further below there is a list of common formula symbols.
Glossary of Photonics Terms
This page summarizes the definitions of photonics terms, as they appear below the headings of many of the Encyclopedia pages.
A | B | C | D | E | F | G | H | I | J | K | L | M |
N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
A
- Abbe number
- a measure for the chromatic dispersion of a transparent material
- ABCD matrix
- a 2-by-2 matrix describing the effect of an optical element on a laser beam
- absorbance
- the logarithm with base 10 of the inverse transmittance
- absorptance
- the fraction of incoming radiant flux which is absorbed by an object
- absorption
- a process where light energy is converted to another form of energy
- absorption coefficient
- a logarithmic measure for the distributed absorption in a medium
- absorption length
- the length over which absorption reduces the optical intensity to 1/e of its initial value
- acceptance angle in fiber optics
- the maximum incidence angle of a light ray which can be used for injecting light into a fiber core or waveguide
- achromatic optics
- optical devices or setups with minimized chromatic aberrations
- acousto-optic deflectors
- acousto-optic devices for deflecting and scanning laser beams
- acousto-optic frequency shifters
- acousto-optic devices for shifting the optical frequency of a laser beam
- acousto-optic modulators
- optical modulators based on the acousto-optic effect
- acousto-optic Q switches
- acousto-optic modulators used for Q switching of lasers
- acousto-optic tunable filters
- acousto-optic devices which can be used for filtering light, controlled with an RF input
- actinometry
- a field of metrology which is based on counting radiation quanta instead of registering powers
- active fibers
- optical fibers containing laser-active dopants in the fiber core
- active mode locking
- a technique of mode locking, based on active modulation of the intracavity losses or the round-trip phase change
- adaptive optics
- a class of techniques where wavefront distortions are actively compensated
- additive-pulse mode locking
- a technique for mode locking a laser, using a nonlinear interaction in an external resonator
- adiabatic soliton compression
- a pulse compression technique based on the adaptation of solitons to slowly varying propagation parameters
- afocal optical systems
- optical systems which output parallel rays for parallel input rays
- alexandrite lasers
- solid-state lasers based on alexandrite (Cr3+:BeAl2O4) crystals
- alignment lasers
- lasers used for alignment purposes
- alignment sensitivity of optical resonators
- the sensitivity of a laser, an optical resonator or some other device with respect to misalignment
- all-solid-state lasers
- laser systems containing solid-state devices only, in particular no discharge lamps or gas or dye lasers
- amplification factor
- the factor by which the power of a signal is amplified
- amplified spontaneous emission
- a process where spontaneously emitted radiation (luminescence) is amplified
- amplifier chains
- amplifiers consisting of several stages
- amplifier noise
- noise introduced to a signal in an amplifier device
- amplitude-squeezed light
- light with an intensity noise below the shot noise level
- anamorphic prism pairs
- prisms pairs for reshaping laser beams
- anti-reflection coatings
- optical thin-film coatings for reducing reflections from surfaces
- aperture stops
- apertures which limit the angular range of received input light of imaging systems
- arc lamps
- gas discharge lamps based on an electrical arc, or continuously operating gas discharge lamps
- argon ion lasers
- gas lasers based on light amplification in ionized argon in a gas discharge
- arrayed waveguide gratings
- optical filter or multiplexer devices based on arrays of waveguides
- aspheric optics
- optical elements with non-spherical surfaces
- astigmatism
- a kind of optical aberrations; alternatively, a defect of optical lenses or a property of laser beams
- autocollimators
- optical instruments for precisely measuring angular alignments
- autocorrelators
- devices for measuring the intensity or field autocorrelation function of light, mostly used for determining the duration of ultrashort pulses
- avalanche photodiodes
- photodiodes with internal signal amplification through an avalanche process
- axicons
- lenses with a conical surface
B
- B integral
- a measure of the nonlinear phase shift of light, e.g. in an amplifier
- Babinet–Soleil compensators
- adjustable waveplates (retarder plates) containing three birefringent plates
- balanced photodetection
- a method of photodetection which is sensitive to differences in optical powers but not to common noise
- ball lenses
- lenses which have the geometric form of a sphere
- band gap
- a range of energies for which there are no states of carriers in a medium
- bandwidth
- the width of some frequency or wavelength range
- bandwidth-limited pulses
- pulses with a duration as short as possible with their optical spectrum
- bandwidth–distance product
- product of length and maximum signal bandwidth of a fiber-optic link
- beam collimators
- devices for collimating optical beams
- beam combining
- a class of techniques for power scaling of laser sources by combining the outputs of multiple devices
- beam delivery systems
- optical systems for sending laser beams from sources to applications
- beam divergence
- a measure for how fast a laser beam expands far from its focus
- beam dumps
- devices for blocking and absorbing light beams
- beam expanders
- optical devices for modifying the beam radius of a collimated beam
- beam homogenizers
- devices for producing beam profiles with homogeneous intensity distribution
- beam parameter product
- product of the beam radius in a focus and the far-field half-angle beam divergence
- beam pointing fluctuations
- fluctuations of the propagation direction of a laser beam
- beam profilers
- devices for measuring the intensity profile of a laser beam
- beam quality
- a measure for how well a laser beam can be focused
- beam radius
- a measure of the transverse extension of a light beam
- beam shapers
- optical devices for modifying the shapes of laser beams
- beam shutters
- devices for blocking or releasing light beams
- beam splitters
- devices for splitting a laser beam into two or more beams
- beam waist
- location with minimum beam radius
- beat note
- an oscillation of the optical intensity arising from the superposition of light with different optical frequencies
- Beer–Lambert law
- a relation for the dependence of absorption coefficients on concentrations
- bend losses
- propagation losses in an optical fiber (or other waveguide) caused by bending
- Berek compensators
- tunable phase retardation plates containing a single uniaxial crystal
- birefringence
- the polarization dependence of the refractive index of a medium
- birefringent phase matching
- a technique of phase matching based on the birefringence of a crystal material
- birefringent tuners
- devices for wavelength tuning of lasers, based on birefringence and polarization rotation
- bit error rate
- average fraction of wrongly transmitted bits in a communication link
- black coatings
- coatings with strong light absorption
- blue lasers
- lasers emitting blue light
- Bragg gratings
- reflecting structures with a periodic refractive index modulation
- Bragg mirrors
- mirror structures based on Bragg reflection at a period structure
- Brewster plates
- coplanar plates inserted into beams at Brewster's angle
- Brewster windows
- transparent plates which are oriented at Brewster's angle such that parasitic reflection losses are minimized.
- Brewster's angle
- an angle of incidence at which there is no reflection of p-polarized light at an uncoated optical surface
- brightness
- a term mostly used in a qualitative way, related to the output power and beam quality of a laser; quantitatively: often used instead of radiance or luminance
- brightness converters
- optically pumped devices where the generated optical output has a higher brightness than the optical pump source
- Brillouin scattering
- a nonlinear scattering effect involving acoustic phonons
- broad area laser diodes
- laser diodes with a strongly asymmetric shape of the emitting region
- bulk lasers
- lasers based on bulk crystals as gain media
- burst mode lasers
- lasers which emit burst (bunches) of light pulses
C
- cameras
- optical instruments for recording still or moving images
- cardinal points
- a set of points which characterize the function of an optical element or a group of elements in Gaussian optics
- carrier–envelope offset
- the offset between the optical phase and the maximum of the wave envelope of an optical pulse
- causality
- the concept of relating effects to causes, or the compatibility of phenomena with this concept
- cavities
- resonators for light (or for microwaves)
- cavity dumping
- a method for extracting intense short or ultrashort pulses from a laser, using an optical switch in the laser resonator
- ceramic laser gain media
- laser gain media which have a ceramic (polycrystalline) microscopic structure
- channel waveguides
- waveguides with the form of a channel at the surface of a host medium
- chemiluminescence
- luminescence arising from chemical reactions
- chirp
- time dependence of the instantaneous frequency of an optical pulse
- chirped mirrors
- Bragg-type dispersive mirrors with a spatial variation of the Bragg wavelength
- chirped-pulse amplification
- a technique for amplifying pulses to very high optical intensities while avoiding excessive nonlinear pulse distortions or optical damage
- chromatic aberrations
- image distortions caused by wavelength-dependent optical effects
- chromatic dispersion
- the frequency dependence of the phase velocity in a transparent medium
- chromaticity
- an objective specification of measured or calculated colors, used in addition to luminance (brightness)
- chromium-doped laser gain media
- laser gain media doped with chromium ions
- CIE standard illuminants
- standardized optical spectra for white light sources
- cladding mode strippers
- devices which can remove light from a fiber cladding
- cladding modes
- modes in optical fibers (or other waveguides) which are not restricted to the region around the core
- cleaning of optics
- cleaning of optical elements
- cleaving of fibers
- preparing fiber ends with clean optical surfaces by controlled breaking
- clustering
- the tendency e.g. of laser-active ions in laser gain media to form clusters in their host medium
- coherence
- a fixed phase relationship between the electric field values at different locations or at different times
- coherence length
- a measure of temporal coherence, expressed as the propagation distance over which the coherence significantly decays
- coherence time
- a measure of temporal coherence, expressed as the time over which the field correlation decays
- coherent beam combining
- a class of methods for beam combining, requiring mutual coherence of the combined beams
- coherent states
- a special kind of pure quantum-mechanical states of light
- cold mirrors
- mirrors which can reduce the heat load in an optical system by reflecting only visible radiation
- collimated beams
- laser beams with weak divergence
- color centers
- crystal defects which introduce additional light absorption or emission features in crystalline materials
- color rendering index
- a quantity which can be used for estimating how accurately colors can be perceived when using a specific light source
- color spaces
- mathematical spaces for representing color values
- color temperature
- the temperature of a blackbody radiator which leads to a color impression of the thermal light which matches most closely the light of a light source
- color vision
- vision with some capability for spectral analysis of the light
- colorimeters
- instruments for measuring quantities which are relevant for color perception
- colorimetry
- the science and technology of objectively measuring optical properties related to color impressions for the human eye
- common-path interferometers
- interferometers where the sensitivity to mechanical noise is reduced by largely using a common optical path for the interfering light beams
- composite laser crystals
- laser crystals consisting of several parts of different materials or with different chemical compositions (e.g. doping concentrations)
- condensers
- lenses or lens systems for conditioning light from an illumination source
- confocal scanning microscopes
- optical microscopes with enhanced depth resolution based on the confocal measurement principle
- conjugate planes
- pairs of planes where an optical system images one into the other and vice versa
- continuous-wave operation
- operation mode of a laser with continuous light emission
- cooperative lasing
- the phenomenon that laser action at one wavelength can facilitate lasing at another wavelength
- core-less end caps
- end pieces attached to optical fibers, containing no fiber core
- corner cube prisms
- prisms with three reflecting surfaces which act as retroreflectors
- CO2 lasers
- infrared lasers based on a gas mixture in which light is amplified by carbon dioxide molecules
- critical phase matching
- phase matching of a nonlinear interaction by adjustment of a propagation direction
- cross-phase modulation
- a nonlinear effect where the optical intensity of one beam influences the phase change of another beam
- crown glasses
- optical glasses with low chromatic dispersion and tentatively a low refractive index
- cryogenic lasers
- lasers where the gain medium is operated at cryogenic temperatures
- crystal ovens
- temperature-controlled ovens for keeping optical crystals at the desired operation temperature
- crystalline mirrors
- multilayer mirrors where the reflecting parts consist of a monocrystalline material
- custom optics
- optical elements made according to customer-specific specifications
- cut-off wavelength
- a wavelength above which a guided mode of a waveguide ceases to exist
- cylindrical lenses
- lenses which focus or defocus light only in one direction
D
- dark current
- a current from a photodetector which occurs even in the absence of a light input
- dBm
- dB relative to a reference power of 1 mW
- decibel
- a logarithmic measure for power ratios, applied e.g. to optical powers or to noise powers
- deformable mirrors
- mirrors which can be deformed in a controlled manner, e.g. for wavefront correction in adaptive optics
- delayed nonlinear response
- the phenomenon that the nonlinear polarization of a medium does not instantly follow the electric field strength
- depolarization loss
- losses of optical power in a laser resonator, caused by depolarization e.g. in a laser crystal
- depth of field
- the distance between the nearest and furthest objects that can be imaged with reasonably sharp focus for a given focus setting
- depth of focus
- the half width of the range of longitudinal positions in which a reasonable focus for a film or image sensor is achieved
- detectivity
- the inverse of the noise equivalent power
- diameter–divergence product
- product of the diameter (at a beam waist) and the divergence angle of a laser beam
- diaphragms
- circular (or approximately circular) openings through which light can travel
- dichroic mirrors
- mirrors with significantly different reflection or transmission properties at two different wavelengths
- dichroism
- wavelength-dependent transmission, alternatively polarization-dependent absorption
- dielectric coatings
- thin-film coatings made of transparent dielectric materials, e.g. for laser mirrors or anti-reflection coatings
- dielectric materials
- electrically insulating materials
- dielectric mirrors
- mirrors consisting of multiple thin layers of different transparent optical materials
- differential mode delay
- the range of time delay values for signals in a telecom fiber
- diffraction
- wave phenomena which occur when light waves hit some structure with variable transmission or phase changes
- diffraction gratings
- optical components containing a periodic structure which diffracts light
- diffraction-limited beams
- beams with a minimum possible beam divergence for a given waist radius
- diffractive optics
- optical elements with operation principles based on diffraction of light
- diffusers
- devices which scatter light such that its spatial coherence is substantially reduced
- diode bars
- a type of semiconductor laser containing a one-dimensional array of broad-area emitters
- diode lasers
- semiconductor laser devices based on laser diodes
- diode stacks
- arrangements of multiple diode bars, delivering very high output power
- diode-pumped lasers
- solid-state lasers which are pumped with laser diodes
- dioptric power
- the inverse of the focal length
- direct diode lasers
- diode lasers which are directly used e.g. for material processing
- dispersion
- the dependence of the phase velocity in a medium on the optical frequency or the propagation mode
- dispersion compensation
- the control of the overall chromatic dispersion of a system by adding optical elements with a suitable amount of dispersion
- dispersion compensation modules
- modules used for dispersion compensation
- dispersion management
- the use of tailored chromatic dispersion to enhance the function of optical devices or systems
- dispersion-decreasing fibers
- optical fibers where the chromatic dispersion changes monotonously along the propagation direction
- dispersion-shifted fibers
- fibers with a non-standard zero dispersion wavelength
- dispersive mirrors
- mirrors which provide some amount of chromatic dispersion for the reflected beam
- dispersive wave
- a linearly propagating wave which is split off by a soliton wave under certain conditions
- distance measurements with lasers
- measurements of distances using laser light
- distributed amplifiers
- fiber amplifiers in fiber-optic data links, where the amplification occurs within a large length of transmission fiber
- distributed Bragg reflector lasers
- lasers containing distributed Bragg reflectors as end mirrors
- distributed feedback lasers
- lasers where the whole laser resonator consists of a periodic structure, in which Bragg reflection occurs
- divided-pulse amplification
- a method of amplifying intense ultrashort pulse while avoiding excessive nonlinear effects
- doped insulator lasers
- lasers with a solid-state gain medium containing a laser-active dopant
- doping concentration
- the concentration of some dopant, e.g. of laser-active ions in a laser gain medium
- Doppler broadening
- broadening of the linewidth of atomic transitions, caused by random motion of the emitting atoms
- Doppler cooling
- a technique of laser cooling based on velocity-dependent absorption processes
- Doppler limit
- a limit for the temperature which is achievable with certain laser cooling techniques
- double pulses
- two closely spaced optical pulses
- double-clad fibers
- optical fibers with different waveguide structures for pump and signal light
- dye lasers
- lasers based on liquid or solid dyes as gain media
E
- edge-emitting semiconductor lasers
- semiconductor lasers emitting light along the plane of the wafer
- effective mode area
- a quantitative measure of the area which a waveguide or fiber mode effectively covers in the transverse dimensions
- effective nonlinear coefficient
- a coefficient for quantifying the strength of a nonlinear interaction
- effective refractive index
- a number quantifying the phase delay per unit length in a waveguide, relative to the phase delay in vacuum
- effective transition cross-sections
- a modified type of transition cross-sections which apply to optical transitions between Stark level manifolds
- electro-optic effect
- the phenomenon that the refractive index of a material can be modified with an electric field
- electro-optic modulators
- optical modulators based on the electro-optic effect
- electro-optic sampling
- an optical sampling technique based on the electro-optic effect
- electro-optics
- the science and technology around the electro-optic effect; alternatively: optoelectronics or even the whole area of photonics
- electroabsorption modulators
- optical modulators based on the Franz–Keldysh effect
- electroluminescence
- luminescence arising from electrical influences
- electronic dispersion compensation
- a method for mitigating the effects of chromatic dispersion in fiber-optic communication links with electronic components in the receiver
- emissivity
- a measure for how strongly an object emits and absorbs thermal radiation
- end pumping
- a technique of optically pumping a laser medium in a direction along the laser beam
- energy transfer
- the phenomenon that dopant ions in laser-active media can exchange excitation energy among each other
- enhancement cavities
- optical cavities for exploiting the resonant enhancement of the power of circulating light
- entrance and exit pupil
- the apparent apertures of an optical system, seen from the object or image side
- erbium-doped fiber amplifiers
- fiber amplifiers based on erbium-doped optical fibers
- erbium-doped laser gain media
- laser gain media doped with erbium ions
- erbium-ytterbium-doped laser gain media
- laser gain media which are doped with both erbium (Er) and ytterbium (Yb)
- etalons
- monolithic interferometric devices containing two parallel reflecting surfaces
- evanescent waves
- waves with rapidly decaying amplitude and no power transport
- excimer lamps
- gas discharge lamps where ultraviolet radiation is generated by spontaneous emission from excited dimers
- excimer lasers
- lasers where optical amplification occurs in a plasma containing excited dimers (or other molecules) with an anti-binding electronic ground state
- excited-state absorption
- absorption of light by ions or atoms in an excited electronic state, rather than in the electronic ground state
- external-cavity diode lasers
- non-monolithic diode lasers where the laser cavity (resonator) is completed with external optical elements
- eye-safe lasers
- lasers emitting in a wavelength region with relatively low hazards for the human eye
F
- f-number
- a measure for the open aperture of a photographic objective
- Fabry–Pérot interferometers
- interferometers consisting of two highly reflecting mirrors, forming a standing-wave resonator
- Fabry–Pérot laser diodes
- a laser diode with a laser resonator exhibiting substantial reflections at both ends, but no distributed reflections inside
- Faraday circulators
- a non-reciprocal optical device sending light from each input to the next output port
- Faraday effect
- the rotation of the linear polarization direction in a medium exposed to a magnetic field
- Faraday isolators
- optical isolators based on the Faraday effect
- Faraday mirrors
- the combination of a Faraday rotator and a mirror
- Faraday rotators
- devices which can rotate the polarization state of light, exploiting the Faraday effect
- femtosecond lasers
- lasers emitting light pulses with durations between a few femtoseconds and hundreds of femtoseconds
- few-mode fibers
- fibers supporting only few guided modes
- fiber amplifiers
- optical amplifiers with doped fibers as gain media
- fiber arrays
- a one- or two-dimensional array of optical fibers
- fiber Bragg gratings
- reflective structures in the core of an optical fiber with a periodic or aperiodic perturbation of the effective refractive index
- fiber bundles
- bundles of optical fibers
- fiber cables
- cables containing one or several optical fibers
- fiber cladding
- the area(s) around the core of an optical fiber
- fiber cleavers
- instruments for preparing fiber ends with clean optical surfaces
- fiber coils
- some length of optical fiber wound up to a coil
- fiber collimators
- devices for collimating the light coming from a fiber, or for launching collimated light into the fiber
- fiber connectors
- connectors used as terminations of optical fiber cables
- fiber core
- the region in an optical fiber which guides light
- fiber couplers
- fiber devices for coupling light from one or several input fibers to one or several output fibers, or from free space into a fiber
- fiber fabrication
- the fabrication of optical fibers
- fiber fuse
- the effect that an optical fiber "burns" from the output end under the influence of an intense laser beam launched into the other end
- fiber joints
- permanent or removable connections between fiber ends
- fiber lasers
- lasers with a doped fiber as gain medium, or (sometimes) just lasers where most of the laser resonator is made of fibers
- fiber lasers versus bulk lasers
- Fiber lasers are based on fiber waveguides, while bulk lasers are based on bulk laser crystals.
- fiber launch systems
- optical systems for launching light into optical fibers
- fiber loop mirrors
- fiber loops which act as reflectors
- fiber optics
- optics based on optical fibers
- fiber patch cables
- a protected and connectorized fiber-optic cable
- fiber patch panels
- devices with multiple ports for fiber-optic connectors
- fiber polarization controllers
- devices which allow one to control the state of polarization of light within fibers
- fiber preforms
- a piece of glass from which an optical fiber can be drawn
- fiber shuffles
- arrangements for routing some number of fiber inputs to some fiber outputs, with a fixed or reconfigurable routing matrix
- fiber simulation software
- software for numerical simulations on fiber devices
- fiber splices
- joints between fibers for efficient transfer of light from one fiber to the other
- fiber to the home
- the technology of providing data connections to private homes via optical fibers rather than electric cables
- fiber-coupled diode lasers
- diode laser devices where the generated light is coupled into an optical fiber
- fiber-optic attenuators
- optical attenuators for use in fiber optics, usually used with fiber connectors
- fiber-optic links
- optical communication links where the signal light is transported in fibers
- fiber-optic networks
- communication systems consisting of fiber-optic links
- fiber-optic plates
- transparent plates containing many optical fibers
- fiber-optic pump combiners
- fiber-optic couplers for sending pump and signal light into an amplifier or laser fiber
- fiber-optic sensors
- optical sensors based on fiber devices
- fiber-optic tapers
- fiber-optic plates which are tapered for obtaining some image magnification
- fibers
- a kind of long and thin optical waveguides which can be bent to some degree
- field lenses
- lenses in imaging instruments which affect the field of view
- field of view
- the angular extent of the field which can be observed with an optical instruments or the eye
- field stops
- apertures which limit the field of view of imaging systems
- finesse
- the free spectral range divided by the FWHM width of the resonances of an optical resonator
- first surface mirrors
- metal-coated mirrors reality metallic mineral coating is on the front surface of the mirror substrate
- Fizeau interferometers
- interferometers for investigating optical surfaces
- flash lamps
- gas discharge lamps which are used for generating intense light pulses
- flat optics
- optics realized with flat and thin devices
- flat-top beams
- a light beam with a flat intensity profile
- flint glasses
- optical glasses with strong chromatic dispersion (low Abbe number) and tentatively a high refractive index
- fluence
- optical energy per unit area
- fluorescence
- luminescence arising from irradiation with light
- fluorescence microscopy
- a technique for acquiring microscopic images using fluorescence which is excited in the sample
- fluorescence spectroscopy
- spectroscopy which is based on the analysis of fluorescence light
- fluorescent lamps
- lamps which emit fluorescent light, usually generated by irradiation of a phosphor with light from an electric gas discharge
- fluoride fibers
- optical fibers based on fluoride glasses
- fluoride glasses
- glasses made from compounds of fluorine e.g. with zirconium, aluminum or indium
- focal distance
- the distance between an objective and its focal point
- focal length
- a measure of how strongly an optical system focuses or defocuses light
- focal plane arrays
- arrays of light detectors placed in the focal plane of an imaging system
- focal points and focal planes
- points to which parallel input rays are concentrated by an optical system, and the planes going through those points
- focus
- a point where different light rays meet, the optimum adjustment of an imaging system, or a location along a beam where the beam diameter reaches a minimum
- forbidden transitions
- transitions between different energy levels of some atoms or ions for which dipole transitions are suppressed via symmetries
- four-level and three-level laser gain media
- laser gain media without/with reabsorption from the lower laser level
- four-wave mixing
- an interaction of light waves based on a <$\chi^{(3)}$> nonlinearity
- Fourier optics
- the description of light propagation based on transverse spatial Fourier transforms
- Fourier transform spectroscopy
- a method for spectroscopy rare an optical spectrum is computed from raw data with a Fourier transform
- free electron lasers
- laser devices where light amplification occurs by interaction with fast electrons in an undulator
- free spectral range
- frequency spacing of the axial modes of an optical resonator
- free-space optical communications
- optical data transmission through free space, usually through air or vacuum, often involving a laser beam
- frequency combs
- optical spectra consisting of equidistant lines
- frequency doubling
- the phenomenon that an input wave in a nonlinear material can generate a wave with twice the optical frequency
- frequency metrology
- the field of technology dealing with precise frequency measurements
- frequency noise
- noise of the instantaneous frequency of an oscillating signal
- frequency quadrupling
- the phenomenon that an input laser beam generates a beam with four times the optical frequency
- frequency tripling
- the phenomenon that an input laser beam generates a beam with three times the optical frequency
- frequency-resolved optical gating
- a technique for the complete characterization of ultrashort optical pulses
- frequency-stabilized lasers
- lasers where the optical frequency of the output is made particularly stable
- Fresnel equations
- equations for the amplitude coefficients of transmission and reflection at the interface between two transparent homogeneous media
- Fresnel lenses
- lenses where the surface profile has annular steps
- Fresnel number
- a parameter determining the regime of diffraction effects
- Fresnel reflections
- light reflections at optical interfaces
- fundamental mode locking
- mode locking with a single pulse circulating in the laser resonator
- fused silica
- amorphous silicon dioxide
- fusion splicing of fibers
- a technique of making low-loss fiber joints by fusing fiber ends together
- Füchtbauer–Ladenburg equation
- an equation used for calculating emission cross-sections of laser gain media
G
- gain
- a measure of the strength of optical amplification
- gain bandwidth
- the width of the optical frequency range in which significant gain is available from an amplifier
- gain clamping
- a firm limitation of the gain of some amplifier or laser, usually caused by lasing action
- gain efficiency
- small-signal gain of an optical amplifier per unit pump power or per unit stored energy
- gain equalization
- a technique for making the gain spectrum of an optical amplifier device flatter over a certain optical frequency range
- gain guiding
- guiding of light based on spatially inhomogeneous optical gain
- gain narrowing
- the phenomenon that the bandwidth of light can be reduced during amplification in a medium with a limited gain bandwidth
- gain saturation
- the phenomenon that the gain of an amplifier is reduced for high input signal powers
- gain switching
- a technique for generating short optical pulses in a laser by modulating the laser gain
- gas cells
- a cell filled with some gas, normally used in laser absorption spectroscopy
- gas discharge lamps
- light sources which are based on an electrical discharge in an ionized gas or metal vapor
- gas lasers
- lasers with a gas (or plasma) as gain medium
- Gaussian beams
- light beams where the electric field profile in a plane perpendicular to the beam axis can be described with a Gaussian function, possibly with an added parabolic phase profile
- Gaussian optics
- a framework for describing optical phenomena, which is based on geometrical optics and the paraxial approximation
- Gaussian pulses
- pulses with a temporal intensity profile which has a Gaussian shape
- geometrical optics
- a concept of optics which is based on the propagation of light rays, ignoring wave properties of light
- germanate fibers
- optical fibers based on germanate glasses
- Giles parameters
- spectroscopic data concerning absorption and amplification in an active fiber
- Gires–Tournois interferometers
- linear optical resonators used for introducing chromatic dispersion
- glass lasers and amplifiers
- solid-state lasers with a glass as gain medium
- Gordon–Haus jitter
- a timing jitter originating from fluctuations of the center frequency
- Gouy phase shift
- an additional phase shift occurring in the propagation of focused Gaussian beams
- graded-index fibers
- optical fibers with a continuously varying refractive index in the radial dimension
- gradient-index lenses
- lenses which utilize a radial variation of refractive index
- green lasers
- lasers emitting in the green spectral region
- group delay
- a measure of the time delay experienced by narrow-band light pulses in an optical device
- group delay dispersion
- the frequency dependency of the group delay, or (quantitatively) the corresponding derivative with respect to angular frequency
- group index
- the ratio of the vacuum velocity of light to the group velocity in a medium
- group velocity
- the velocity with which the envelope of a weak narrow-band optical pulse propagates in a medium
- group velocity dispersion
- the frequency dependence of the group velocity in a medium, or (quantitatively) the derivative of the inverse group velocity with respect to angular frequency
- group velocity mismatch
- the phenomenon that pulses become temporally separated in a medium due to different group velocities, or (quantitatively) the difference of inverse group velocities
- guided waves
- waves for which diffraction is suppressed by a waveguide structure
H
- halogen lamps
- incandescent lamps with a halogen filling, allowing for higher operation temperatures
- harmonic mode locking
- mode locking of a laser where multiple pulses are circulating in the laser resonator with equal temporal spacing
- Haus Master equation
- an analytical equation describing the evolution of ultrashort pulses in a laser resonator
- helium–neon lasers
- gas lasers based on a helium–neon mixture
- Hermite–Gaussian modes
- propagation modes or resonator modes which are described with Hermite–Gaussian functions
- high brightness laser diodes
- laser diodes with particularly high radiance (brightness)
- high harmonic generation
- the phenomenon that very high harmonics of an intense input laser beam are generated in a gas
- high intensity discharge lamps
- gas discharge lamps operating with high power density
- high-energy lasers
- pulsed lasers with a high output pulse energy
- high-power fiber lasers and amplifiers
- fiber lasers and fiber amplifiers with high output powers of e.g. larger than 100 W
- high-power lasers
- lasers emitting very high optical powers
- higher-order modes
- transverse modes of a resonator or waveguide, excluding the fundamental (axial) modes
- higher-order solitons
- optical pulses in a nonlinear and dispersive medium which exhibit periodic oscillations of their temporal and spectral shape
- highly nonlinear fibers
- optical fibers exhibiting relatively strong nonlinear effects
- hollow-core fibers
- optical fibers with a hole on the fiber axis
- holography
- methods for recording and reconstructing three-dimensional images
- homogeneous broadening
- the increase in the linewidth of an atomic transition caused by effects which affect different radiating or absorbing atoms in the same way
- homogeneous saturation
- saturation of an absorption or gain, where the shape of the absorption or gain spectrum is not modified
- hot mirrors
- mirrors which can reduce the heat load in an optical system by reflecting infrared radiation
- hyper Raman scattering
- Raman scattering processes involving two pump photons
- hyperfocal distance
- the smallest focusing distance of an imaging instruments for which objects at infinity appear with reasonably sharp focus
- hyperspectral imaging
- imaging which provides images with an optical spectrum corresponding to each pixel
I
- illuminance
- the incident luminous flux per unit area on a surface
- image intensifiers and image converters
- instruments which can intensify images acquired under faint light conditions, or convert images to other wavelengths
- image planes
- planes which are conjugate to an object plane, so that objects are imaged there
- image sensors
- optoelectronic sensors which can be used for imaging
- imaging
- mapping objects points to image points; applications involving such methods
- imaging with a lens
- creation of an optical image using a single lens
- in-band pumping
- optical pumping of a laser or amplifier directly from the lower to the upper laser level, or at least directly into the upper laser level
- incandescent lamps
- light sources which produce thermal radiation from an electrically heated filament
- index matching fluids
- fluids with a refractive index similar to that of other optical materials, typically used for suppressing light reflections
- industrial lasers
- lasers used for industrial purposes, for example for laser material processing
- infrared cameras
- cameras which work with infrared light
- infrared detectors
- detectors for infrared light
- infrared emitters
- devices emitting infrared radiation
- infrared light
- invisible light with wavelengths roughly between 750 nm and 1 mm
- infrared optics
- optical elements and systems which are suitable for infrared light
- infrared viewers
- instruments for observing scenes with infrared light
- inhomogeneous broadening
- the increase in the linewidth of an atomic transition caused by effects which act differently on different radiating or absorbing atoms
- inhomogeneous saturation
- gain saturation effects which alter the shape of the gain spectrum
- injection locking
- a technique for enforcing operation of a laser on a certain optical frequency by injecting light with that frequency into the laser resonator
- injection seeding
- a technique for enforcing narrowband operation of a laser or optical parametric oscillator by injecting light into its resonator
- insertion loss
- power losses due to insertion of a device
- instantaneous frequency
- temporal derivative of the oscillation phase divided by <$2\pi$>
- integrated optics
- the technology dealing with the construction of photonic integrated circuits
- integrating spheres
- devices with a diffusely reflecting inner surface, used for certain optical measurements
- intensity modulators
- devices which can be used to modulate the intensity (power) of a light beam
- intensity noise
- noise of the optical intensity or power of a laser beam
- interference
- a range of phenomena associated with the superposition of waves
- interference filters
- optical filters based on interference effects
- interferometers
- optical devices utilizing the phenomenon of interference
- interlocks
- safety devices for automatically switching off a laser power or interrupting a laser beam
- intermodal dispersion
- the phenomenon that the group velocity of light propagating in a waveguide structure depends on the waveguide mode
- intracavity frequency doubling
- frequency doubling with a nonlinear crystal within the laser resonator
- intracavity laser absorption spectroscopy
- a method of laser spectroscopy, based on the evolution of the optical spectrum of intracavity radiation under the influence of narrowband absorption features
- intracavity pumping
- pumping a laser or OPO with intracavity radiation from another laser
- ion lasers
- gas lasers where ions are used as laser-active agents
- irradiance
- the radiant flux (optical power) received by a surface per unit area
J
K
- Kelly sidebands
- sidebands in the spectrum of certain mode-locked lasers, related to a periodic disturbance of soliton pulses in the laser resonator
- Kerr effect
- a nonlinear interaction of light in a medium with an instantaneous response, related to the nonlinear electronic polarization
- Kerr lens
- a lensing effect arising from the Kerr nonlinearity
- Kerr lens mode locking
- a technique for mode locking a laser, exploiting nonlinear self-focusing
- Kramers–Kronig relations
- mathematical relations between absorption coefficient and refractive index of media
- Kuizenga–Siegman theory
- a theory predicting the durations of pulses from actively mode-locked lasers
L
- Lambertian emitters and scatterers
- light emitters or scatters where the radiance towards an observer is independent of the viewing direction
- lamp power supplies
- power supplies for lamps
- lamp-pumped lasers
- lasers which are pumped with flash lamps or arc lamps, or in rare cases with tungsten halogen lamps
- large diameter optics
- optical elements with a diameter of e.g. 100 mm or more
- large mode area fibers
- optical fibers with relatively large mode areas and a single transverse mode or only a few modes
- large-core fibers
- optical fibers with relatively large fiber core
- laser 3D printing
- the fabrication of 3D structure using laser sintering, melting or polymerization
- laser ablation
- the removal of solid material using intense laser light
- laser absorption spectroscopy
- methods of absorption spectroscopy using laser light
- laser additive manufacturing
- laser-based processes which create suitably shaped solid parts from a powder or liquid
- laser applications
- applications involving laser devices
- laser beam characterization
- methods of assessing detailed properties of laser beams
- laser beams
- light beams propagating dominantly in one direction
- laser cladding
- the deposition of a metallic cladding layer on a metallic base surface, aided by laser light
- laser cleaning
- the removal of unwanted substances from surfaces by applying intense laser radiation
- laser coating
- the deposition of a coating layer on a base surface, aided by laser light
- laser cooling
- a variety of techniques for reducing the temperature (i.e., the random motion) of small particles such as atoms or ions
- laser cooling units
- devices used for cooling of high-power lasers
- laser crystals
- transparent crystals with laser-active dopants, used as laser gain media
- laser cutting
- cutting of material using intense laser beams
- laser design
- the design of a laser device, or the process of working out such a design
- laser development
- the process of developing a laser device
- laser diode collimators
- devices for collimating the output of laser diodes
- laser diode drivers
- electronic current supplies for one or several laser diodes
- laser diode modules
- modules containing diode lasers, and possibly also some optics, cooling devices, electrical elements, etc.
- laser diode testing
- various test procedures applied to laser diodes in qualification, regular batch testing or burn-in
- laser diodes
- semiconductor lasers with a current-carrying p–n junction as the gain medium
- laser drilling
- the generation of holes with laser beams
- laser dynamics
- the temporal evolution of quantities such as the optical power and gain in a laser
- laser gain media
- media for laser amplification
- laser glasses
- doped glasses which can be used as laser gain media
- laser guide stars
- small bright spots in the sky, generated with laser beams for use in astronomy with adaptive optics imaging
- laser hardening
- hardening materials (usually steel or cast iron) with a laser treatment
- laser heads
- assemblies containing a mounted gain medium and means for pumping and cooling, or the complete optical parts of a laser, or assemblies for directing a laser beam to a workpiece
- laser light
- light generated with a laser device
- laser line optics
- optical elements made specifically for certain laser lines
- laser lines
- narrow spectral lines obtained from lasers
- laser machining
- methods of laser material processing which involve the controlled removal of material
- laser marking
- a group of methods for labeling materials with lasers
- laser material processing
- a general term for a wide range of methods for material processing using laser radiation
- laser micromachining
- machining with laser radiation on a micrometer scale
- laser microscopy
- a technique for generating microscopic images by scanning objects with a laser
- laser mirrors
- high-quality mirrors used in laser resonators and other optical setups
- laser modeling and simulation
- the investigation of phenomena and quantitative relations in lasers, using theoretical models, computational methods and simulation; used for problem analysis and design optimization
- laser noise
- fluctuations of various parameters of laser light, such as the optical power and phase
- laser optics
- optical elements and systems used with lasers - either in lasers or for transmitting and manipulating laser light
- laser physics
- the field of physics dealing with phenomena in lasers
- laser pointers
- devices used for pointing at items with laser beams
- laser processing heads
- the part of a laser processing machine which is used to direct a laser beam to a workpiece
- laser rangefinders
- devices for measuring distances to objects, using lasers
- laser resonators
- optical resonators serving as basic building blocks of lasers
- laser rods
- laser crystals (or glasses) in the form of (usually cylindrical) rods
- laser safety
- safety of the use of laser devices
- laser safety glasses
- the protection of eyes against laser hazards
- laser scanners
- devices for scanning the direction of a laser beam
- laser soldering
- joining parts with a solder, which is heated with a laser beam
- laser specifications
- descriptions of essential properties of a laser system, such as performance parameters, dimensions, and operating conditions
- laser speckle
- light patterns resulting from the reflection of coherent light at rough surfaces
- laser spectroscopy
- methods where the interaction of laser light with matter is utilized
- laser surface modification
- the modification of surface properties of materials using processes with laser beams
- laser threshold
- an operation condition of a laser where laser emission just starts to occur
- laser transitions
- optical transitions where stimulated emission is used to obtain optical amplification
- laser viewing cards
- cards used for visualizing laser beams in non-visible spectral regions
- laser welding
- joining of parts by melting them with a laser beam
- laser-induced breakdown
- a kind of spark, initiated by intense laser light
- laser-induced damage
- damage of optical components induced by laser radiation
- lasers
- devices generating visible or invisible light, based on stimulated emission of light
- lasers for material processing
- lasers which are suitable for application in laser material processing
- lasers for quantum photonics
- lasers which are specifically suitable for applications in quantum photonics
- lasers for Raman spectroscopy
- lasers which are specifically suitable for applications in Raman spectroscopy
- lasing without inversion
- the quantum-optical phenomenon of laser emission occurring without the presence of a population inversion
- leaky modes
- a concept for quasi-bound waveguide modes with propagation losses due to leakage into the cladding
- lenses
- transparent optical devices affecting the wavefront curvature of light
- LIDAR
- a technique for acquiring 3D images with laser pulses
- light
- electromagnetic radiation in the visible spectral range, or sometimes in an extended spectral region
- light beams
- light which propagates essentially in one direction and has a limited spatial extension in directions perpendicular to its beam direction
- light forces
- forces associated with absorption, reflection or scattering of light
- light pulses
- flashes of light
- light-emitting diodes
- semiconductor diodes that emit light via electroluminescence
- linewidth
- width of the spectrum of a light beam or an absorption feature
- linewidth enhancement factor
- a parameter quantifying the amplitude–phase coupling in a laser
- liquid crystal displays
- displays based on liquid crystal modulators
- liquid crystal modulators
- optical modulators which are based on liquid crystals
- loupes
- optical lenses held close to the eye which are used for viewing objects with some moderate magnification
- lower-state lifetime
- the lifetime of the population in the lower laser level in the absence of radiation
- LP modes
- linearly polarized modes of optical fibers with radially symmetric index profiles in the approximation of weak guidance
- luminance
- luminous flux per unit solid angle and unit projected area
- luminescence
- light emission which is not caused by heating
- luminosity
- radiant flux (among other meanings)
- luminosity functions
- functions describing the spectral sensitivity of the human eye
- luminous efficacy and efficiency
- the luminous flux of a light source divided by its the radiant power or its electrical consumption (efficacy); the ratio of reached efficacy to the theoretically possible efficacy (luminous efficiency)
- luminous flux
- a measure of the perceived power of light, e.g. from a light source
- luminous intensity
- luminous flux per unit solid angle
- Lyot filters
- optical filter devices based on birefringence, exhibiting a wavelength-dependent transmission
M
- M2 factor
- a parameter for quantifying the beam quality of laser beams
- magnification
- the enlargements of images
- magnifying glasses
- optical lenses held above objects for viewing them with some moderate magnification
- master laser
- a single-frequency laser used for injection locking one or several other lasers
- master oscillator fiber amplifier
- a laser system containing a fiber amplifier for boosting the output power
- master oscillator power amplifier
- a laser system consisting of a seed laser and a laser amplifier for boosting the output power
- McCumber theory
- a theory applied to absorption and emission properties of laser gain media, in particular to solid-state media
- mechanical fiber splices
- permanent or semi-permanent connections of optical fibers which are held in place with mechanical means
- medical lasers
- laser systems used for medical applications
- mercury vapor lamps
- metal vapor lamps based on light emission from mercury (Hg) atoms
- metal halide lamps
- gas discharge lamps containing metal halides
- metal vapor lamps
- light sources which are based on an electrical discharge in a metal vapor
- metal vapor lasers
- gas lasers utilizing a metal vapor as gain medium
- metal-coated mirrors
- mirrors where the reflection is obtained from a metal coating
- metal–semiconductor–metal photodetectors
- fast photodetector devices based on metal–semiconductor (Schottky) contacts
- metastable states
- excited states (particularly electronic states in laser gain media) which have a relatively long lifetime due to slow radiative and non-radiative decay
- Michelson interferometers
- an interferometer with two separate arms and a single beam splitter
- micro-optics
- the field of optics dealing with particularly small optical components
- microbends of fibers
- microscopic bends of optical fibers
- microchannel plates
- electron amplifiers with many spatial channels
- microchip lasers
- solid-state lasers with a quasi-monolithic setup
- microlens arrays
- one- or two-dimensional arrays of microlenses, used e.g. in Shack-Hartmann wavefront sensors
- microlenses
- optical lenses of particularly small diameter, e.g. below 1 mm
- microscope objectives
- the optical component of a microscope which is next to the observed object
- microscopes
- instruments for seeing very small objects
- mid-infrared fibers
- optical fibers for use with mid-infrared light
- mid-infrared laser sources
- light sources emitting mid-infrared radiation in the form of a laser-like beam
- mid-infrared spectrometers
- spectrometers which can analyze mid-infrared light
- miniature lasers
- lasers with particularly small geometric dimensions
- mirror substrates
- substrates on which coatings for laser mirrors can be deposited
- mirrors
- devices which reflect light
- modal bandwidth
- the maximum optical bandwidth (limited by intermodal dispersion) which can be used in a telecom fiber
- mode cleaner cavities
- optical cavities used as filters for improving the beam quality of laser beams
- mode cleaners
- devices which can improve the beam quality of laser beams
- mode competition
- the phenomenon that different resonator modes experience laser amplification in the same gain medium, leading to cross-saturation effects
- mode coupling
- a concept for describing and calculating light propagation in certain situations, e.g. involving nonlinear interactions
- mode division multiplexing
- a multiplexing technique for data transmission in fibers, where different fiber modes are used for different channels
- mode field converters
- optical devices which allow for efficient coupling between modes of different sizes
- mode hopping
- the phenomenon that a laser exhibits sudden jumps of optical frequency, which are associated with transitions between different modes of its resonator
- mode locking
- a group of techniques for generating ultrashort pulses in lasers
- mode locking devices
- devices for achieving mode locking of a laser
- mode matching
- the precise spatial matching of the electric field distributions of laser beams and resonator modes or waveguide modes
- mode radius
- a measure of the transverse extent of a laser mode or laser beam
- mode-locked diode lasers
- diode lasers which are actively, passively or hybrid mode-locked for generating ultrashort pulses
- mode-locked fiber lasers
- ultrafast fiber lasers which are actively or passively mode-locked for generating ultrashort pulses
- mode-locked lasers
- lasers which emit ultrashort pulses on the basis of the technique of mode locking
- modes
- self-consistent electric field distributions in waveguides, optical resonators or in free space
- modes of laser operation
- a mode of operation such as continuous-wave operation, Q-switched or mode-locked operation
- modulation depth
- a relative modulation amplitude, or (for a saturable absorber) the maximum change in absorption
- modulational instability
- a nonlinear optical effect which amplifies modulations of optical power
- molecular lasers
- gas lasers where the laser-active gas consists of molecules rather than separate atoms or ions
- monochromatic light
- light with a single optical frequency
- monochromators
- optical devices which transmit only light in an adjustable small range of optical wavelengths
- monolithic solid-state lasers
- solid-state lasers where the whole laser resonator consists only of one piece of crystal or glass
- multi-core fibers
- optical fibers containing more than one fiber core
- multi-line lasers
- laser sources emitting radiation on multiple laser lines
- multi-phonon transitions
- transitions between electronic levels of atoms or ions in solid media, involving the emission of multiple phonons
- multimode beams
- light beams in free space or in transparent media which involve multiple (often many) modes, frequently with highly random characteristics
- multimode fibers
- fibers supporting more than one guided mode per polarization direction
- multipass amplifiers
- an amplifier with multiple passes through the gain medium
- multipass gas cells
- a cell which allows to realize multiple passes of a laser beam through a gas
- multiphonon absorption
- absorption processes involving multiple phonons
- multiphoton absorption
- absorption processes where multiple photons are absorbed simultaneously
- multispectral imaging
- imaging which provides images with multiple spectral channels
N
- nanofibers
- optical fibers with transverse dimensions below one micrometer
- nanosecond lasers
- lasers emitting optical pulses with nanosecond durations
- narrow-linewidth lasers
- single-frequency lasers with a narrow optical emission spectrum
- near field and far field
- the optical field either close to a source or object or far from it
- neodymium-doped laser gain media
- laser gain media containing laser-active neodymium ions
- neutral density filters
- optical attenuators with an approximately constant attenuation in a substantial wavelength range
- night vision devices
- instruments which allow viewing or imaging under conditions of very low light levels
- nodal points
- points of an optical system for which an incoming ray, directed at a nodal point, leaves the system with the same direction.
- noise eaters
- devices for reducing the intensity noise of an optical beam by automatically adjusting the degree of power attenuation
- noise figure
- a measure of the excess noise added in an amplifier
- noise specifications
- specifications for the noise properties of lasers, for example
- noise-equivalent power
- the input power to a detector which produces the same signal output power as the internal noise of the device
- non-radiative transitions
- transitions between energy levels of atoms or ions which are not associated with the emission of light
- nonclassical light
- light with properties which can be explained only within quantum optics
- noncritical phase matching
- a technique of phase matching which does not require a critical angular adjustment
- nonlinear absorption
- absorption where the absorption coefficient depends on the optical intensity
- nonlinear crystal materials
- crystal materials exhibiting an optical nonlinearity, usually of <$\chi^{(2)}$> type
- nonlinear frequency conversion
- the conversion of input light to light of other frequencies, using optical nonlinearities
- nonlinear index
- a parameter for quantifying the Kerr nonlinearity of a medium
- nonlinear length
- the propagation distance in a medium over which nonlinear effects become substantial
- nonlinear optics
- the part of optics dealing with optical nonlinearities and their applications
- nonlinear polarization
- the part of the light-induced electric polarization which depends nonlinearly on the electric field of the light
- nonlinear polarization rotation
- the phenomenon that the change in the polarization direction of light in a fiber can depend on the optical intensity
- nonlinear pulse distortion
- distortion of the spatial, temporal or spectral characteristics of an optical pulse, resulting from optical nonlinearities
- nonlinearities
- optical phenomena involving a nonlinear response to a driving light field
- nonplanar ring oscillators
- a type of monolithic single-frequency lasers, based on a nonplanar ring resonator
- numerical aperture
- the sine of the acceptance angle of an optical system or a waveguide
O
- object and image space
- mathematical spaces for the description of optical elements and systems
- objectives
- optical elements for collecting light from inspected objects, or for sending light to objects
- ocular lenses
- lenses or lens systems as used in telescopes and microscopes, for example, close to the observing eye
- OEM laser modules
- laser modules made for integration into larger devices by another manufacturer
- opacity
- the property of a substance or an object not to transmit light or at least to attenuate it
- optical aberrations
- degradations of optical images caused in imaging instruments
- optical activity
- the ability of a transparent substance to exhibit polarization rotation or circular dichroism
- optical adhesives
- specialty adhesives for use in optical systems, usually with high transparency for light
- optical amplifiers
- devices for amplifying the power of light beams
- optical apertures
- structures which limit the propagation of light
- optical attenuators
- devices which can reduce the optical power e.g. of a light beam
- optical breadboards
- portable platforms for optical prototyping and for mounting modules on optical tables
- optical choppers
- devices for periodically interrupting light beams
- optical clocks
- time measurement devices based on optical frequency standards
- optical clockworks
- devices which can phase-coherently relate optical frequencies to microwave frequencies
- optical coherence tomography
- an optical imaging technique where longitudinal resolution is achieved based on interference effects with low-coherence light
- optical contact
- a close and clean contact between two solids where light can be transmitted without significant wavefront distortions
- optical contact bonding
- a method of generating an optical contact by directly (without a contact agent) merging two surfaces of transparent solids with very high surface quality
- optical crystals
- crystals for optical applications, usually single crystals, often with polished end faces
- optical data transmission
- the transmission of information using light beams, e.g. in fibers
- optical delay lines
- an optical setup which is used to introduce a time delay for a light beam
- optical density
- a logarithmic measure of the power attenuation, or the refractive index
- optical domes
- strongly curved optical windows
- optical energy meters
- instruments for measuring optical pulse energies
- optical fabrication
- the fabrication of optical components like lenses, prisms and mirrors
- optical fiber communications
- the technology of transmitting information through optical fibers
- optical filters
- devices with a wavelength-dependent transmission or reflectance
- optical flats
- plates with one or two surfaces of very high optical quality and flatness
- optical frequency
- the oscillation frequency of the electric field of light
- optical frequency multipliers
- devices which convert light to other light with optical frequencies which are integer multiples of the original frequency
- optical frequency standards
- frequency standards using optical transitions in atoms, ions or molecules
- optical glasses
- glasses of high quality, made for optical applications
- optical heterodyne detection
- a sensitive method of photodetection, reaching the standard quantum limit even for weak signal powers
- optical intensity
- optical power per unit area
- optical isolators
- devices which transmit light in one direction but not in the opposite direction
- optical materials
- materials used for optical components
- optical metrology
- the science and technology of performing measurements with light
- optical modulators
- devices allowing one to manipulate properties of light beams, such as the optical power or phase
- optical molasses
- an arrangement of laser beams used for cooling atoms or ions
- optical parametric amplifiers
- optical amplifiers based on parametric nonlinear interactions
- optical parametric chirped-pulse amplification
- parametric amplification of chirped ultrashort pulses
- optical parametric generators
- light sources based on parametric amplifiers with no signal or idler input
- optical parametric oscillators
- coherent light sources based on parametric amplification within an optical resonator
- optical path length
- product of physical path length and refractive index
- optical phase
- the phase of the electric field of an optical wave, usually considered in the time domain
- optical physics
- the study of the fundamental physics aspects of optics
- optical power
- the energy per unit time, e.g. transported by a laser beam, or a focusing power
- optical power meters
- instruments for optical power measurements, based e.g. on heating of an absorber structure or a photodiode
- optical power monitors
- devices for monitoring optical powers in free-space light beams or in optical fibers
- optical profilometers
- optical non-contact instruments for precisely measuring surface profiles
- optical pumping
- electronically exciting a medium with light, or specifically populating certain electronic levels
- optical rectification
- a nonlinear process where an optical field generates a quasi-DC nonlinear polarization
- optical refrigeration
- a technique for cooling macroscopic samples via laser-induced fluorescence
- optical resonators
- arrangements of optical components which allow a beam of light to circulate
- optical sampling
- a technique of sampling signals using laser light, often in the form of ultrashort pulses
- optical sensors
- sensors based on optical principles, or sensors for light
- optical slits
- narrow openings through which light can be transmitted
- optical spectrum
- the decomposition of the power or energy of light according to different wavelengths or optical frequencies
- optical spectrum analyzers
- instruments for measuring optical spectra
- optical strain sensors
- sensors for mechanical strain based on optical technology, e.g. with fiber Bragg gratings
- optical tables
- platforms for building optical devices with suppression of vibrations
- optical temperature sensors
- temperature sensors based on optical technology, e.g. with fiber Bragg gratings
- optical thickness
- a measure either for the absorption or the effective optical path length of a sample
- optical time-domain reflectometers
- instruments for measuring the spatially resolved reflectivities and losses in optical fibers
- optical tweezers
- arrangements for capturing and moving particles with laser beams
- optical windows
- flat transparent plates with optical quality, used for protection against the environment
- optics
- the science and technology dealing with the properties and the propagation of light
- opto-isolators
- optoelectronic devices for signal transmission with electrical isolation between two electrical circuits
- opto-mechanics
- mechanical elements used in optics
- optoelectronics
- the technology of electronic devices that interact with light
- orientation-patterned semiconductors
- semiconductors containing a periodic pattern of domain orientation
- oscillators
- a device producing an oscillation – in contrast to an amplifier, for example
- output couplers
- partially transparent laser mirrors, used for extracting output beams from laser resonators
- output coupling efficiency
- a factor influencing the power efficiency of a laser, taking into account intracavity losses
P
- parabolic mirrors
- mirrors with the surface shape of a paraboloid, or at least a parabolic cross-section
- parabolic pulses
- pulses with a parabolic intensity profile
- parametric amplification
- a process of optical amplification based on a parametric nonlinearity
- parametric fluorescence
- emission of light by a parametric amplifier without signal or input inputs
- parametric nonlinearities
- instantaneous optical nonlinearities based on the <$\chi^{(2)}$> or <$\chi^{(3)}$> nonlinear tensor of a transparent medium
- parasitic lasing
- unwanted laser operation in a laser or amplifier device
- paraxial approximation
- a frequently used approximation, essentially assuming small angular deviations of the propagation directions from some beam axis
- passive fibers
- optical fibers without laser-active dopants in the fiber core
- passive mode locking
- a technique of mode locking, based on a saturable absorber inside the laser resonator
- peak power
- maximum optical power of a pulse
- periodic poling
- a technique for achieving quasi-phase matching of nonlinear interactions in a transparent crystal material
- phase corrector plates
- transparent plates for modifying the phase profile of light
- phase matching
- a group of techniques for achieving efficient nonlinear interactions in a medium
- phase modulators
- devices for manipulating the phase of a laser beam
- phase noise
- noise of the optical phase of a beam or of an electric signal
- phase shift method for distance measurements
- a method for optical distance measurements
- phase velocity
- the velocity with which phase fronts propagate in a medium
- phase-matching bandwidth
- the width of an optical frequency range in which some process (e.g. a nonlinear interaction) can be efficient due to sufficiently precise phase matching
- phonons
- quantized microscopic vibrations in solid media
- phosphate glasses
- certain glasses from which certain optical fibers and laser gain media can be made, for example
- phosphorescence
- a luminescence which lasts for a relatively long time after excitation of a medium
- phosphors
- substances which exhibit luminescence, used mostly for illumination and displays
- photo cameras
- optical instruments for taking photographic images
- photocathodes
- an electrode where electrons can be released based on the photoelectric effect
- photochromic materials
- optical materials which exhibit increased light absorption when being exposed to light
- photoconductive detectors
- photodetectors which exhibit a reduction in electrical resistance caused by incoming light
- photoconductive sampling
- a technique of optical sampling with photoconductive switches
- photoconductive switches
- electric switches controlled by light via photo-induced conductivity
- photocurrent
- an electric current which is induced by incident light in a photodetector
- photodarkening
- the phenomenon that the optical power losses in a medium can grow when the medium is irradiated with light at certain wavelengths
- photodetectors
- devices used for the detection of light
- photodiode arrays
- typically linear arrays of photodiodes, provided as compact devices
- photodiodes
- semiconductor devices with a p–n or p–i–n structure for the detection of light
- photoelectric effect
- the emission or excitation of electric carriers related to the absorption of light
- photoemissive detectors
- photodetectors which are based on the external photoelectric effect
- photographic objectives
- objective lenses used for photography
- photoluminescence
- emission of light which is caused by the irradiation of a material with other light
- photometers
- instruments for measuring light properties such as irradiance or illuminance, or optical properties of objects
- photometry
- the science and technology of measuring properties of light related to its perceived brightness for human eyes
- photomultipliers
- photodetection devices based on the photoelectric effect and charge multiplication by secondary emission of electrons
- photon counting
- photodetection at low light levels where single photon absorption events are counted
- photonic bandgap fibers
- optical fibers where light is guided based on a photonic bandgap effect
- photonic crystal fibers
- specialty optical fibers with a built-in microstructure, in most cases consisting of small air holes in glass
- photonic crystal surface-emitting lasers
- surface-emitting semiconductor lasers utilizing a 2D photonic crystal structure for forming an in-plane laser resonator
- photonic crystals
- media with special optical properties due to periodic optical nanostructures
- photonic integrated circuits
- integrated circuits with optical functions
- photonic metamaterials
- nanostructured materials with special optical properties
- photonic metasurfaces
- surfaces containing sub-wavelength structures which lead to special optical properties
- photonics
- the science and technology of light
- photons
- quanta of light energy
- phototransistors
- a type of semiconductor-based photodetector with internal current amplification for higher responsivity
- phototubes
- gas-filled or vacuum tubes which can be used as photodetectors
- photovoltaic cells
- semiconductor devices which generate electrical energy from light energy
- picosecond diode lasers
- diode lasers emitting picosecond light pulses
- picosecond lasers
- lasers emitting pulses with picosecond durations
- pinholes
- circular holes, typically with diameters well below one millimeter
- planar waveguides
- waveguide structures guiding light only in one dimension
- plane waves
- waves with plane wavefronts
- plastic optical fibers
- optical fibers made of polymer materials
- plastic optics
- optical elements made of organic polymer materials
- Pockels cell drivers
- electronic devices for driving Pockels cells
- Pockels cells
- electro-optic devices, used for building modulators
- Pockels effect
- the phenomenon that the refractive index of a medium exhibits a modification which is proportional to the strength of an applied electric field (linear electro-optic effect)
- polarimeters
- instruments for measuring the rotation angle of optical polarization caused by optically active substances
- polarization beam combining
- a technique for combining two polarized laser beams
- polarization beat length
- the period of interference effects in a birefringent medium
- polarization mode dispersion
- the polarization dependence of the propagation characteristics of light waves in optical fibers
- polarization of light
- direction of the electric field oscillation of a light beam
- polarization waves
- patterns of electric (or magnetic) polarization of a medium which are usually caused by light waves
- polarization-maintaining fibers
- specialty optical fibers with strong built-in birefringence, preserving the properly oriented linear polarization of an input beam
- polarizers
- optical filters where the light transmission depends strongly on the direction of polarization
- polishing of fibers
- the polishing of fiber ends in order to obtain particularly well-defined optical properties
- polychromatic light
- light with multiple optical frequencies
- polychromators
- an optical device which sends light with different wavelengths to different directions
- population inversion
- a state of a medium where a higher-lying electronic level has a higher population than a lower-lying level
- position-sensitive detectors
- photodetectors which can detect the position of a light spot in one or two dimensions
- power density
- intensity or power per unit frequency interval
- power over fiber
- delivery of power for electronic devices via light in an optical fiber which is converted to electricity
- power scaling of lasers
- a procedure for substantially increasing the output power of lasers
- power spectral density
- optical power or noise power per unit frequency interval
- Poynting vector
- a vector indicating the strength and direction of energy flow of an electromagnetic wave
- principal dispersion
- a crude measure for chromatic dispersion of a transparent optical material
- principal points and principal planes
- planes from which rays appear to be deflected in an optical system according to paraxial optics, and the intersections of those planes with the optical axis
- prism pairs
- combinations of two prisms, mostly used for dispersion compensation
- prisms
- transparent optical devices which refract or reflect light
- propagation constant
- a mode- and frequency-dependent quantity describing the propagation of light in a medium or waveguide
- propagation losses
- losses of optical energy during propagation of light
- pulse characterization
- the measurement of various properties of an optical pulse
- pulse compression
- linear or nonlinear techniques for reducing the durations of optical pulses
- pulse duration
- the duration of an optical pulse
- pulse energy
- energy of an optical pulse
- pulse front tilt
- the phenomenon that the arrival time of an ultrashort pulse varies across the beam profile
- pulse generation
- the generation of light pulses (flashes)
- pulse pickers
- electrically controlled optical switches used for extracting single pulses from a pulse train
- pulse propagation modeling
- working with physical models describing the propagation of ultrashort pulses e.g. in lasers or optical fibers
- pulse repetition rate
- the number of pulses emitted per second e.g. by a mode-locked or Q-switched laser
- pulse shapers
- devices which can be used to modify the temporal or spectral shape of ultrashort light pulses
- pulse stretchers
- devices for temporally stretching ultrashort light pulses
- pulse trains
- regular sequences of pulses
- pulsed laser deposition
- a method for fabricating thin films on substrates by evaporating materials with laser pulses
- pulsed lasers
- lasers emitting light in the form of pulses
- pump absorption
- the absorption of pump light, e.g. in a laser or a laser amplifier
- pump chambers
- a part of a lamp-pumped solid-state laser, containing a laser rod, one or more lamps, reflectors, a cooling arrangement and possibly other parts
- pump depletion
- reduction in the transmitted pump power in a laser or nonlinear conversion device
- pump parameter
- the ratio of pump power and threshold pump power of a laser
- pump–probe measurements
- techniques for investigating ultrafast phenomena, where a pump pulse excites a sample and a probe pulse is used for probing the sample after an adjustable delay time
- pyroelectric detectors
- light detectors based on the pyroelectric effect
- p–i–n photodiodes
- photodiodes with a p–i–n semiconductor structure
Q
- Q factor
- a measure of the damping of resonator modes
- Q switches
- optical switches which are typically used for generating nanosecond pulses in lasers
- Q switching
- a method for obtaining energetic pulses from lasers by modulating the intracavity losses
- Q-switched lasers
- lasers which emit optical pulses, relying on the method of Q switching
- Q-switched mode locking
- an operation regime of mode-locked lasers with strong fluctuations of the pulse energy
- Q-switching instabilities
- instabilities of passively mode-locked lasers where the pulse energy is unstable
- quantum cascade lasers
- semiconductor lasers relying on intersubband transitions, normally emitting in the mid-infrared spectral region
- quantum cryptography
- methods to encrypt information securely, relying on quantum-mechanical phenomena
- quantum defect
- energy difference between pump and laser photons
- quantum dots
- microscopic structures confining charge carriers in three dimensions
- quantum efficiency
- percentage of input photons which contribute to a desired effect
- quantum electronics
- an area of physics which is the basis of optoelectronics
- quantum key distribution
- methods for the secure distribution of encryption keys
- quantum noise
- noise arising from quantum fluctuations
- quantum optics
- the part of optics which deals with quantum effects
- quantum photonics
- the science and technology using quantum optics for applications like quantum communications, quantum computing and quantum metrology
- quantum wells
- thin layers confining carriers in one dimension
- quarter-wave mirrors
- dielectric mirrors based on a sequence of quarter-wave layers
- quasi-continuous-wave operation
- an operation mode of lasers (e.g. diode bars) where the pump power is switched on for short time intervals in order to limit thermal effects
- quasi-phase matching
- a technique of achieving a kind of phase matching, using a periodic structure
- quasi-soliton pulses
- soliton-like pulses in lasers or fiber-optic links
- quasi-three-level laser gain media
- laser gain media where the lower laser level has a substantial thermally induced population
- quenching
- the reduction or limitation of an excited-state population, mostly by unwanted effects
R
- Rabi oscillations
- oscillations of level populations (or quantum mechanical probability amplitudes) under the influence of an incident light field
- radiance
- the optical power per unit area and solid angle
- radiant energy
- energy of some electromagnetic radiation which is emitted, transmitted or absorbed during some interval of time
- radiant exitance
- radiant flux emitted by a surface per unit area
- radiant flux
- radiant energy per unit time which is emitted, transmitted, reflected or received by an object
- radiant intensity
- radiant flux per unit solid angle
- radiation pressure
- a mechanical pressure resulting from incident light or other radiation
- radiation-balanced lasers
- lasers where the heat generation in the gain medium is compensated by optical refrigeration in the same medium
- radiation-resistant fibers
- optical fibers which exhibit relatively little performance degradation when exposed to high-energy gamma or other radiation
- radiative lifetime
- lifetime of an electronic state in the (hypothetical) situation where only radiative processes depopulate that level
- radio and microwave over fiber
- the transmission of radio frequency signals through optical fibers
- radiometry
- the science and technology of measuring properties of electromagnetic radiation, including light
- Raman amplifiers
- optical amplifiers based on Raman gain
- Raman gain
- optical gain arising from stimulated Raman scattering
- Raman gain media
- nonlinear media in which stimulated Raman scattering can be utilized for obtaining optical amplification
- Raman lasers
- lasers based on Raman gain rather than on laser gain from stimulated emission
- Raman scattering
- a nonlinear scattering process involving optical phonons
- Raman spectroscopy
- optical spectroscopy based on spontaneous or stimulated Raman scattering
- rare-earth-doped fibers
- optical glass fibers which are doped with rare earth ions
- rare-earth-doped laser gain media
- laser gain media which are doped with rare earth ions
- rate equation modeling
- a method of modeling the dynamics of laser gain media
- Rayleigh length
- the distance from a beam waist where the mode radius increased by a factor square root of 2
- Rayleigh scattering
- scattering of light at scattering centers which are much smaller than the wavelength
- reciprocity method
- a spectroscopic method which is often used for obtaining the scaling of emission spectra of laser gain media
- recirculating fiber loops
- fiber loops in which light can circulate many times
- recoil limit
- a lower limit for the temperature which can be reached with some laser cooling techniques
- red lasers
- lasers emitting red light
- reference cavities
- optical cavities serving as a kind of frequency reference
- reflectance
- the ratio of reflected optical power to the incident optical power at some reflecting object
- reflectivity
- the ratio of reflected optical power to the incident optical power at a surface
- reflectometers
- instruments for measuring the reflectance of objects
- reflectors
- devices which reflect light or other radiation
- refraction
- the change of the propagation direction when a wave comes from one medium into another one
- refractive index
- a measure of the reduction in the velocity of light in a medium
- refractometers
- scientific instruments used to measure the refractive index of materials
- regenerative amplifiers
- optical amplifiers with a resonator in which a light pulse can do multiple round trips before being coupled out
- relative intensity noise
- noise of the optical intensity (or actually power), normalized to its average value
- relaxation oscillations
- small mutually coupled oscillations of the laser power and laser gain around their steady-state values
- resonant frequency doubling
- frequency doubling with a nonlinear crystal placed in a resonant enhancement cavity
- resonator design
- the description of the optical components from which an optical resonator is made, and their exact arrangement
- resonator modes
- modes (self-reproducing field configurations) of an optical or microwave resonator
- responsivity
- photocurrent per unit optical power incident on a photodetector
- retardance
- the difference in optical phase shifts between two polarization directions, e.g. for light transmitted through a sample or reflected at a surface
- retroreflectors
- optical devices which reflect light in a direction which is parallel to the incident beam
- return loss
- a measure for how much reflected light is attenuated
- RGB sources
- source of red, green and blue light, which is usually provided in the form laser beams
- ring lasers
- lasers with a ring resonator
- ring resonators
- optical resonators where light can independently circulate in two different directions
- rod lasers
- solid-state lasers with a rod-shaped gain medium
- rod lenses
- cylindrical lenses with the geometrical form of a cylinder
- ruby lasers
- solid-state lasers based on a ruby crystal
- rugate filters
- dielectric interference filters with a continuous variation of the refractive index
S
- saturable absorbers
- light absorbers with a degree of absorption which is reduced at high optical intensities
- saturable Bragg reflectors
- a special type of saturable semiconductor absorbers
- saturation energy
- a measure of the incident optical pulse energy required for achieving significant saturation of an absorber or a gain medium
- saturation power
- a measure of the incident optical power required for achieving significant saturation of an absorber or a gain medium
- scanning lenses
- lens systems which are designed for use in laser scanners
- scattering
- processes where light is sent in other directions, usually but not always in random directions
- Schawlow–Townes linewidth
- linewidth of a single-frequency laser with quantum noise only
- scientific lasers
- lasers which are designed for scientific applications
- scotopic and photopic vision
- vision of the human eye at lower and higher light intensity levels, respectively
- sech2-shaped pulses
- pulses with a temporal intensity profile which has the shape of a sech2 function
- seed lasers
- lasers which are used for generating some seed light into an amplifier or another laser
- self-focusing
- focusing of a beam in a transparent medium, caused by the beam itself through a nonlinear process in the medium
- self-heterodyne linewidth measurement
- a technique for laser linewidth measurements, based on a beat note between the beam and a delayed version of itself
- self-phase modulation
- nonlinear phase modulation of a beam, caused by its own intensity via the Kerr effect
- self-starting mode locking
- mode locking which is quickly achieved after turning on a laser, without external intervention
- self-steepening
- a nonlinear effect in pulse propagation, leading to an increasingly steep trailing slope of the temporal pulse shape
- self-terminating laser transitions
- laser transitions which can not be continuously operated due to the accumulation of population in the lower laser level
- Sellmeier formula
- an equation for calculating the wavelength-dependent refractive index of a medium
- semiconductor lasers
- lasers based on semiconductor gain media
- semiconductor optical amplifiers
- optical amplifiers based on semiconductor gain media
- semiconductor saturable absorber mirrors
- saturable semiconductor absorber devices acting as nonlinear mirrors
- semiconductors
- materials with a small band gap energy
- sensitivity
- (different meanings, depending on the context)
- Shack–Hartmann wavefront sensors
- wavefront sensors which are based on a microlens array
- shot noise
- quantum-limited intensity noise
- side pumping
- a technique of pumping a solid-state laser in directions which are approximately transverse to its beam direction
- sign conventions in wave optics
- conventions concerning the signs of phase terms in wave optics
- signal lamps
- lamps for displaying or sending light signals
- signal-to-noise ratio
- the ratio of signal power to noise power in a detector
- silica fibers
- optical fibers based on fused silica or related materials
- silicate glasses
- glasses which are based on silica (silicon dioxide) and some additions
- silicon photonics
- photonic technology based on silicon chips
- single-atom lasers
- lasers with only a single atom as the gain medium
- single-crystal fibers
- long and thin rods made of monocrystalline materials
- single-frequency lasers
- lasers emitting radiation in a single resonator mode
- single-frequency operation
- an operation mode of a laser where only a single resonator mode acquires a significant power
- single-mode fibers
- optical fibers supporting only a single guided mode per polarization direction
- single-mode operation
- operation of a laser on axial (longitudinal) resonator modes only, or even on a single axial mode
- single-polarization fibers
- optical fibers which transmit only light with a certain polarization
- Sisyphus cooling
- a mechanism for laser cooling of atoms or ions
- slab lasers
- solid-state bulk lasers where the gain medium has the form of a slab
- slave laser
- a laser which is injection-locked to another laser
- slope efficiency
- differential power efficiency of a laser
- small-signal gain
- optical gain for small signal intensities, where no amplifier saturation occurs
- sodium vapor lamps
- metal vapor lamps based on light emission from sodium (Na) atoms
- solar modules
- devices for solar power generation, containing photovoltaic cells
- solar power generation
- the generation of electricity based on sunlight
- solar-blind photodetectors
- photodetectors which are insensitive to visible light but react to ultraviolet light
- solid-state lasers
- lasers based on solid-state gain media (usually ion-doped crystals or glasses)
- soliton mode locking
- a mechanism for laser mode locking based on soliton pulses
- soliton period
- the distance over which higher-order solitons reproduce their temporal and spectral shape
- solitons
- pulses with a certain balance of nonlinear and dispersive effects
- space division multiplexing
- a multiplexing technique for optical data transmission where multiple spatial channels are utilized
- space-qualified lasers
- lasers which have been qualified for use in space missions, where the need to fulfill special conditions
- spatial hole burning
- a distortion of the gain shape in a laser medium (or the loss spectrum in a saturable absorber medium), caused by saturation effects of a standing wave
- spatial walk-off
- the phenomenon that the intensity distribution of a beam in an anisotropic crystal drifts away from the direction of the wave vector
- specialty fibers
- optical fibers with special designs or materials
- spectral beam combining
- a class of methods for beam combining, based on wavelength-sensitive beam combiners
- spectral brightness
- brightness per unit optical bandwidth
- spectral imaging
- imaging which also provides spectral information
- spectral lamps
- low pressure gas discharge lamps emitting light on one or more standard spectral lines
- spectral lines
- narrow spectral features related to emission or absorption lines of certain substances
- spectral phase
- the phase of the electric field in the frequency domain
- spectral phase interferometry
- a class of interferometric methods for pulse characterization, where interference in the frequency domain is exploited
- spectral quantities
- quantities in radiometry and photometry which describe the distribution e.g. of a radiant flux over different optical frequencies or wavelengths
- spectral response of a photodetector
- the range of optical wavelengths for which a photodetector is sensitive
- spectrograms
- a type of diagrams which visualize optical or other signals
- spectrographs
- instruments for spectrally analyzing light, based on a polychromator and a multi-channel photodetector
- spectrometers
- devices for separating spectral components
- spectrophotometers
- instruments for measuring the wavelength-dependent transmittance or reflectance of solutions or solid objects
- spectroscopy
- methods where the interaction of light with matter is utilized, e.g. for detecting substances or measuring concentrations
- specular reflection
- reflection of light where the angle of reflected light equals the angle of incident light, but on the opposite side of the surface normal
- spherical aberrations
- optical aberrations resulting from spherical optical surfaces
- spiking
- the tendency of some lasers to emit spikes of output power, particularly after being switched on
- spontaneous emission
- a quantum effect, causing the spontaneous decay of excited states of atoms or ions
- spun fibers
- fibers which have been twisted during the fiber drawing process in order to obtain modified polarization properties
- squeezed states of light
- nonclassical states of light with noise below the standard quantum limit in one quadrature component
- stability zones of optical resonators
- parameter regions of an optical resonator where the resonator is geometrically stable
- stabilization of lasers
- measures applied to lasers in order to improve their stability in terms of output power, optical frequency, or other quantities
- standard quantum limit
- a limit for noise levels set by quantum mechanics
- standard spectral lines
- spectral lines which are often used as wavelength references
- standing-wave resonators
- optical resonators with two end mirrors
- Stark level manifolds
- groups of energy levels (e.g. of laser gain media) which can have slightly different energies due to the Stark effect
- step-index fibers
- optical fibers with a step-index refractive index profile
- stimulated emission
- a quantum effect, where photon emission is triggered by other photons
- Stokes shift
- the reduction in photon energy in certain processes
- streak cameras
- devices for measuring the power of an optical pulse versus time
- sum and difference frequency generation
- nonlinear processes generating beams with the sum or difference of the frequencies of the input beams
- supercontinuum generation
- a nonlinear process for strong spectral broadening of light
- superfluorescence
- collective emission of radiation by an ensemble of excited atoms or ions
- superluminal transmission
- transport of some quantity with a velocity exceeding that of light in vacuum
- superluminescence
- fluorescence which is enhanced by laser amplification
- superluminescent diodes
- broadband semiconductor light sources based on superluminescence
- superluminescent sources
- optical sources based on superluminescence
- supermirrors
- laser mirrors with a very high reflectivity
- superradiance
- collective emission of an ensemble of atoms or ions after coherent excitation
- surface-emitting semiconductor lasers
- semiconductor lasers where the generated light propagates in the direction perpendicular to the wafer surface
- synchronization of lasers
- the synchronization of light pulses generated with lasers
- synchronous pumping
- pumping of a laser or an optical parametric oscillator with short light pulses in synchronism with the emitted pulses
T
- tapered amplifiers
- optical amplifiers which contain a tapered section, where the beam area is gradually increased
- tapered fibers
- optical fibers which are over some length stretched out to a very small diameter
- tapered laser diodes
- laser diodes containing a tapered region for achieving a higher beam quality
- telecentric lenses
- lenses or objectives having the entrance or exit pupil at infinity
- telecom fibers
- optical fibers for use in optical fiber communications
- telescopes
- optical instruments for viewing distant objects, or sometimes more generally afocal systems
- temporal walk-off
- the loss of temporal overlap of pulses, caused by group velocity mismatch
- terahertz detectors
- detectors for terahertz radiation
- terahertz radiation
- electromagnetic radiation with frequencies around 0.1 THz to 10 THz
- terahertz sources
- sources of electromagnetic radiation with frequencies around 0.1 THz to 10 THz
- thermal blooming
- thermally caused distortion and deflection of a laser beam profile for propagation through a gas or liquid with high optical power
- thermal detectors
- light detectors which are based on measuring light-induced temperature rises
- thermal imaging
- imaging based on thermal radiation
- thermal lensing
- a lensing effect induced by temperature gradients
- thermal radiation
- electromagnetic radiation which results from thermal emission
- thin-disk lasers
- solid-state bulk lasers having a very thin disk of laser-active material as the gain medium
- thin-film polarizers
- optical polarizers based on a multilayer dielectric coating
- third-order dispersion
- chromatic dispersion related to a third-order dependence of the phase change on the frequency offset
- threshold pump power
- the pump power at which the laser threshold is reached
- thresholdless lasers
- lasers with a threshold power which is virtually zero
- thulium-doped laser gain media
- laser gain media containing laser-active thulium ions
- time division multiplexing
- a multiplexing technique operating in the time domain
- time-of-flight measurements
- distance measurements based on measuring the time of flight of a light pulse
- time-resolved spectroscopy
- spectroscopy where time-dependent signals are measured
- time–bandwidth product
- product of temporal and spectral width of a pulse
- timing jitter
- fluctuations of the temporal positions of pulses
- timing phase
- a phase reflecting timing deviations by relating them to the pulse period
- titanium–sapphire lasers
- lasers based on a Ti:sapphire gain medium
- total internal reflection
- the phenomenon that light incident on the boundary between two transparent media is fully reflected if the light is coming from the optical more dense medium and the angle of incidence is sufficiently large
- transform limit
- a limit for the time–bandwidth product of an optical pulse
- transition cross-sections
- material parameters for quantifying the likelihood or rate of optical transition events
- transition-metal-doped laser gain media
- laser gain media which are doped with transition metal ions
- transmission gratings
- diffraction gratings which are used in transmission
- transmissivity
- the ratio of transmitted optical power to the incident optical power at a surface
- transmittance
- the ratio of transmitted optical power to the incident optical power at some partial transparent object
- triangulation
- a method for distance measurements
- triple-clad fibers
- optical fibers having three claddings
- tunable lasers
- lasers the output wavelengths of which can be tuned
- tunable optical filters
- optical filters with tunable filter parameters, e.g. concerning center wavelength of pass band
- tungstate lasers
- solid-state lasers based on tungstate crystals as gain media
- twisted-mode technique
- a technique for achieving single-frequency operation of a laser, based on quarter-wave plates on both sides of the gain medium
- two-photon absorption
- a nonlinear absorption process where two photons are simultaneously absorbed
- Twyman–Green interferometers
- an interferometer similar to a Michelson interferometer, but with expanded beams
U
- ultrafast amplifiers
- amplifiers for ultrashort (femtosecond or picosecond) optical pulses
- ultrafast laser physics
- the area of laser physics dealing with ultrashort processes
- ultrafast lasers
- lasers emitting ultrashort pulses
- ultrafast optics
- the part of optics dealing with ultrafast phenomena
- ultrashort pulses
- optical pulses with durations of picoseconds or less
- ultraviolet lasers
- lasers (or other laser-based light sources) generating ultraviolet light
- ultraviolet light
- invisible light with wavelengths shorter than ≈ 400 nm
- ultraviolet optics
- optical elements for use with ultraviolet light
- unstable resonators
- optical resonators which are dynamically unstable with respect to transverse beam offsets
- upconversion
- a process where light can be emitted with photon energies higher than those of the light generating the excitation
- upconversion lasers
- lasers relying on upconversion processes
- upper-state lifetime
- the lifetime of the population in the upper laser level
V
- V number
- a normalized frequency parameter, which determines the number of modes of a step-index fiber
- vacuum noise
- quantum noise of the vacuum state, or quantum noise introduced into an optical system via a vacuum input
- vanadate lasers
- lasers based on rare-earth-doped yttrium, gadolinium or lutetium vanadate crystals, usually Nd:YVO4
- variable optical attenuators
- optical attenuators with a variable degree of attenuation
- variable reflectivity mirrors
- mirrors with a spatial variation of the reflectivity (reflectance)
- VCSEL arrays
- arrays containing many VCSEL laser emitters
- velocity of light
- the velocity with which light propagates in a medium
- velocity-matched photodetectors
- a type of photodetector where propagation velocities of light and electrical signals are matched in order to achieve a very high detection bandwidth
- vertical cavity surface-emitting lasers
- a monolithic kind of semiconductor lasers with beam emission perpendicular to the wafer surface
- vertical external-cavity surface-emitting lasers
- surface-emitting semiconductor lasers with an external laser resonator
- vibronic lasers
- lasers based on gain media with a large gain bandwidth, caused by a strong interaction of electronic transitions with phonons
- vignetting
- a reduction of image brightness in peripheral regions
- visible lasers
- lasers (or other laser-based light sources) emitting visible light
- volume Bragg gratings
- Bragg gratings written into some bulk material
W
- wall-plug efficiency
- total electrical-to-optical power efficiency of a laser system
- wave optics
- the description of optical phenomena based on wave models
- wave vector
- a vector indicating the direction of wave propagation and the phase delay per unit length
- wavefronts
- surfaces connecting points with the same phase of a wave
- waveguide dispersion
- chromatic dispersion arising from waveguiding effects
- waveguide lasers
- lasers with a waveguide structure in the gain medium
- waveguides
- spatially inhomogeneous transparent structures for guiding light
- wavelength
- the spatial period of a plane wave
- wavelength division multiplexing
- a multiplexing technique working in the wavelength domain
- wavelength tuning
- the manipulation of the output wavelength of an optical device such as a laser or an optical parametric oscillator
- wavelength-swept lasers
- lasers which allow for period and fast wavelength tuning
- wavelength-tunable light sources
- light sources where the optical wavelength can be tuned
- wavemeters
- devices for precise measurements of laser wavelengths
- wavenumber
- the phase delay per unit length, or that quantity divided by <$2\pi$>
- waveplates
- transparent plates with a defined amount of birefringence, used for modifying the polarization of light
- wedge prisms
- prisms with a small angle between the end surfaces
- white light
- light which creates a white color impression
- white light interferometers
- interferometers using broadband light inputs
- white light sources
- light sources with very broad optical bandwidth
- working distance
- the distance between an objective and the object
X
- X-ray lasers
- lasers emitting in the X-ray spectral region
- xenon lamps
- lamps based on an electrical discharge in xenon gas
Y
- YAG lasers
- lasers based on YAG (yttrium aluminum garnet) crystals, usually Nd:YAG or Yb:YAG
- yellow and orange lasers
- lasers emitting yellow or orange light
- YLF lasers
- lasers based on YLF (yttrium lithium fluoride) crystals, usually Nd:YLF
- ytterbium-doped laser gain media
- laser gain media containing laser-active ytterbium ions
Z
- z-scan measurements
- a technique for measuring the strength of the Kerr nonlinearity of a material, relying on self-focusing
- zero dispersion wavelength
- a wavelength where the group velocity dispersion of a fiber or a material is zero
- zone plates
- an optical device for focusing light (or other electromagnetic radiation) based on diffraction
List of Formula Symbols
Symbol | Explanation | SI Units |
---|---|---|
<$a$>, <$r_\text{co}$> | core radius of a fiber | m |
<$b$> | confocal parameter of a laser beam (twice the Rayleigh length) | m |
<$c$> | velocity of light | m/s |
<$d_\textrm{eff}$> | effective nonlinear coefficient of a nonlinear crystal material | m/V |
<$D_2$> | group delay dispersion | s2 |
<$D_{2\lambda}$> | group delay dispersion with wavelength derivative | s/m |
<$D_3$> | third-order dispersion | s3 |
<$d_{ij}$> | components of the <$\chi^{(2)}$> nonlinear tensor | m/V |
<$e$> | elementary electric charge | C |
<$f$> | focal length (e.g., of a lens) | m |
<$f$> | noise frequency | Hz |
<$f_\textrm{rep}$> | pulse repetition rate | Hz |
<$f_\textrm{ro}$> | relaxation oscillation frequency | Hz |
<$g$> | gain coefficient | 1 or m−1 |
<$g(\tau )$> | complex degree of coherence | 1 |
<$g_\textrm{B}$> | nonlinear gain coefficient for Brillouin scattering | m/W |
<$g_\textrm{R}$> | nonlinear gain coefficient for Raman scattering | m/W |
<$g_\textrm{ss}$> | small-signal gain coefficient | 1 or m−1 |
<$h$> | Planck's constant | J s |
<$k$> | wavenumber | m−1 |
<$k_\textrm{B}$> | Boltzmann constant | J/K |
<$\Delta k$> | phase mismatch of a parametric nonlinear process | rad/m |
<$l_\textrm{rt}$> | round-trip losses of a resonator | 1 |
<$n$> | refractive index | 1 |
<$n_\textrm{e}$> | extraordinary refractive index | 1 |
<$n_\textrm{eff}$> | effective refractive index | 1 |
<$n_\textrm{g}$> | group index | 1 |
<$n_\textrm{o}$> | ordinary refractive index | 1 |
<$n_2$> | nonlinear index | m2/W |
<$Q$> | Q factor | m |
<$q$> | complex <$q$> parameter (→ Gaussian beams) | m |
<$r$> | radius (e.g., in fiber core or distance from beam axis) | m |
<$r$> | pump parameter of a laser | 1 |
<$r_{ij}$> | components of the electro-optic tensor | m/V |
<$v_\textrm{g}$> | group velocity | m/s |
<$v_\textrm{p}$> | phase velocity | m/s |
<$w$> | Gaussian beam radius | m |
<$w_0$> | beam radius at the beam waist | 1 |
<$z_\textrm{R}$> | Rayleigh length | m |
<$z_\textrm{s}$> | soliton period | m |
<$A$> | amplitude of pulse envelope | |
<$A_\textrm{eff}$> | effective mode area | m2 |
<$B$> | B integral | rad |
<$B$> | noise bandwidth | Hz |
<$B$> | brightness | W/(m2 rad2) |
<$\textrm{BPP}$> | beam parameter product | mm mrad |
<$D_{\lambda }$> | dispersion parameter | ps/(nm km) |
<$E$> | electric field strength | V/m |
<$E_\textrm{p}$> | pulse energy | J |
<$E_\textrm{sat}$> | saturation energy | J |
<$F$> | finesse | 1 |
<$F$> | noise figure | 1 |
<$F_\textrm{sat}$> | saturation fluence | J/m2 |
<$G_X(\tau )$> | autocorrelation function of some variable <$X$> | |
<$I$> | optical intensity | W/m2 |
<$I_\textrm{sat}$> | saturation intensity | W/m2 |
<$L_\textrm{coh}$> | coherence length | m |
<$M^2$> | M2 factor | 1 |
<$N_\textrm{F}$> | Fresnel number | 1 |
<$N_\textrm{dop}$> | doping concentration | m−3 |
<$\textrm{NA}$> | numerical aperture | 1 |
<$P$> | optical power | W |
<$P$> | electric polarization of a medium | C/m2 |
<$P_\textrm{out}$> | output power | W |
<$P_\textrm{p}$> | peak power of a pulse | W |
<$P_\textrm{sat}$> | saturation power of a laser gain medium or saturable absorber | W |
<$Q$> | Q factor | 1 |
<$R$> | power reflectivity (or reflectance) (of a mirror) | 1 |
<$R$> | radius of curvature (e.g., of wavefronts) | m |
<$R$> | responsivity of a photodiode | A/W |
<$\Delta R$> | modulation depth of a saturable absorber | 1 |
<$S_{\varphi }(f)$> | power spectral density of a phase value | rad2/Hz |
<$T$> | temperature | K or °C |
<$T_\textrm{g}$> | group delay | s |
<$T_\textrm{oc}$> | output coupler transmission | 1 |
<$T_\textrm{rt}$> | round-trip time of an optical resonator | s |
<$V$> | V number of a step-index fiber | 1 |
<$\alpha$> | absorption coefficient | m−1 |
<$\alpha$> | linewidth enhancement factor | 1 |
<$\alpha$> | thermal expansion coefficient | K−1 |
<$\beta$> | propagation constant | rad/m |
<$\beta_2$> | group velocity dispersion | s2/m |
<$\gamma_\textrm{SPM}$> | self-phase modulation coefficient | rad/(W m) |
<$\epsilon_0$> | electric permittivity of vacuum | C/Vm |
<$\epsilon$> | relative electric permittivity | 1 |
<$\eta$> | efficiency | 1 |
<$\eta_\textrm{oc}$> | output coupling efficiency | 1 |
<$\theta$> | beam divergence half-angle | rad |
<$\theta$> | polar angle | rad |
<$\kappa$> | thermal conductivity | W/(m K) |
<$\Lambda$> | optical path length | m |
<$\lambda$> | optical wavelength | m |
<$\lambda_\textrm{p}$> | pump wavelength | m |
<$\lambda_\textrm{s}$> | signal wavelength | m |
<$\mu$> | relative magnetic permeability | 1 |
<$\mu_0$> | magnetic permeability of vacuum | N/A2 |
<$\nu$> | optical frequency | Hz |
<$\nu_\textrm{B}$> | Brillouin frequency shift | Hz |
<$\nu_\textrm{ceo}$> | carrier–envelope offset frequency | Hz |
<$\nu (t)$> | instantaneous frequency | Hz |
<$\Delta \nu$> | optical bandwidth | Hz |
<$\rho$> | walk-off angle | rad |
<$\sigma_\textrm{abs}$> | absorption cross-section | m2 |
<$\sigma_\textrm{em}$> | emission cross-section | m2 |
<$\tau_2$> | upper-state lifetime | s |
<$\tau_\textrm{coh}$> | coherence time | s |
<$\tau_\textrm{p}$> | pulse duration | s |
<$\tau_\textrm{rad}$> | radiative lifetime | s |
<$\varphi$> | azimuth angle | rad |
<$\varphi$> | optical phase or phase shift | rad |
<$\varphi_\textrm{G}$> | Gouy phase shift | rad |
<$\varphi_\textrm{nl}$> | nonlinear phase shift from the Kerr effect | rad |
<$\varphi_\textrm{t}$> | timing phase | rad |
<$\Delta \varphi_\textrm{ceo}$> | carrier–envelope offset phase | rad |
<$\chi^{(2)}$>, <$\chi^{(3)}$> | nonlinear tensor | 1 |
<$\omega$> | angular frequency | rad/s, s−1 |
<$\Lambda$> | modulation period of a fiber Bragg grating | m |