Pulsed Lasers

Author: the photonics expert Dr. Rüdiger Paschotta (RP)

Definition: lasers emitting light in the form of pulses

More general term: lasers

Category: article belongs to category light pulses light pulses

DOI: 10.61835/uck Cite the article: BibTex plain text HTML Link to this page! LinkedIn

Pulsed lasers are lasers which emit light not in a continuous mode, but rather in the form of optical pulses (light flashes). The term is most commonly used for Q-switched lasers, which typically emit nanosecond pulses, but this article gives an overview of a wider range of pulse-generating lasers. Depending on the pulse duration, pulse energy, pulse repetition rate and wavelength required, very different methods for pulse generation and very different types of pulsed lasers are used. The article on pulse generation describes more in detail the technical methods, whereas this article discusses some types of pulsed lasers:

Various types of actively or passively Q-switched lasers emit pulses in the nanosecond duration regime; particularly compact microchip lasers can also generate sub-nanosecond pulses. Most Q-switched lasers are solid-state bulk lasers, and some of them can achieve high pulse energies in the millijoule or even multi-joule region.
Some solid-state bulk lasers are pumped with flash lamps but not Q-switched; in free-running mode (i.e., with pulsed pumping but no intracavity loss modulation), one obtains longer pulses and somewhat higher pulse energies.
Excimer lasers are used for generating intense nanosecond pulses in the ultraviolet spectral region. They are pumped with rather short electric pulses.
Some other gas lasers (e.g. nitrogen lasers) and metal vapor lasers (e.g. copper vapor lasers) are also driven with current pulses and could normally not work in continuous-wave operation.
Ultrashort pulses with durations in the picosecond or femtosecond domain are usually generated with mode-locked lasers, which may be solid-state bulk lasers, fiber lasers or semiconductor lasers. Their pulse energies are generally quite small, and the pulse repetition rate is usually in the megahertz or gigahertz region. For higher pulse energies (roughly an order of magnitude more), one may use a cavity-dumped laser.
Gain-switched semiconductor lasers are suitable for nanosecond or picosecond pulses with relatively low energy (→ picosecond diode lasers).
Relatively long pulses can be generated e.g. with laser diodes in quasi-continuous-wave operation.

Difficulties with Continuous-wave Operation

Some types of lasers can hardly work in continuous-wave operation, but only in pulsed operation; that can have different reasons:

It some cases, one can obtain a sufficiently high laser gain only with pump intensities which are practical only for pulsed pumping. For example, the required pump intensities would overheat the gain medium when applied for longer times.
In some cases, one is dealing with self-terminating laser transitions.

For such reasons, one sometimes uses a pulsed laser with a high pulse repetition rate where continuous-wave operation would be fully suitable for the application, but hard to realize with the type of laser. An example is photolithography with excimer lasers.

Difficulties with Long Pulse Durations

While many laser applications benefit from very short pulse durations, there are a few cases where rather long pulses are desired. For example, long pulses allow for a very small optical linewidth and may avoid laser-induced damage due to their lower peak power.

However, it is often quite difficult to produce relatively long laser pulses – for example, with durations of several microseconds –, at least when a high pulse energy is required at the same time. The method of Q switching can be optimized for long pulse durations, but with limitations; for example, it is not practical to use a very long laser resonator to maximize the resonator round-trip time. Another approach is to work with a rather low gain, but that implies a high sensitivity to intracavity losses.

Single-pulse, Repetitive and Burst Mode

Single-pulse Mode

Some pulsed lasers are operated in a single-pulse mode where each pulse can be freely triggered when the application demands it. In that regime, one often achieves rather high pulse energies, but only quite limited pulse repetition rates. It is suitable, for example for lamp-pumped solid-state lasers.

Repetitive Pulsing

Some lasers emit pulses with a constant pulse repetition rate. In the case of Q-switched lasers, this is often between 10 Hz and 100 kHz, while mode-locked lasers emit with very high repetition rates, typically tens or hundreds of megahertz, sometimes even many gigahertz. The energy per pulse is correspondingly low.

The pulse repetition rate may be reduced by some possibly large factor by using a pulse picker.

Burst Mode

For some applications, it is advantageous to use bursts (bunches) of pulses. That means that some number of pulses is emitted with a close temporal spacing (e.g. a couple of nanoseconds), forming a burst, and the next burst may occur only after much longer time.

Many laser types are not suitable for that mode of operation, or only with substantial additional technical effort. A quite flexible approach is to produce pulses with a seed laser diode and amplify those in a fiber amplifier. One may then define a burst simply by appropriately driving the seed laser. In order to compensate for gain saturation during the burst (i.e., a drop of pulse energy), one may apply a seed pulse energy which is rising during the burst.

For more details, see the article on burst mode lasers.

Pulse Quality

There are various aspects of pulse quality, some of which may be quite relevant for applications:

It is often desirable to have very reproducible (constant) pulse parameters like pulse energy, duration, center wavelength and bandwidth. Also, the temporal pulse shape (optical power vs. time) and the evolution of optical phase should be quite constant for some laser applications.
In some cases, it is important to avoid any pre-pulses or post-pulses. For example, in laser-induced nuclear fusion or in other high intensity physics experiments, it is important that the target is “taken by surprise” by an intense laser pulse, and not already evaporated by some unwanted pre-pulse.
The pulse timing can also be important. Some lasers – particularly well stabilized mode-locked lasers – exhibit an extremely small timing jitter, particularly over small measurement time intervals (e.g. pulse-to-pulse jitter).

Amplification of Laser Pulses

For boosting the average power (particularly of high repetition rate pulse trains with moderate pulse energies), high-power fiber amplifiers are often well suited. For cases with lower repetition rate but higher pulse energy, solid-state bulk amplifiers are better suited. These, however, usually do not provide as much gain, unless one uses sophisticated multipass arrangements.

For ultrashort pulses with much increased pulse energies, one uses regenerative amplifiers and multipass amplifiers.

A laser system combined with some kind of optical amplifier is often still called a laser as a whole.

More to Learn

Suppliers

The RP Photonics Buyer's Guide contains 148 suppliers for pulsed lasers. Among them:

Exail

The Exail (formerly iXblue) ModBox-OFE is a complete front end laser system designed to be used as a seed source in high energy density laser facilities. The system is available at 1030 nm, 1053 nm and 1064 nm, it allows to generate custom shaped optical pulses with high stability and high extinction ratio and with durations from 125 ps to 100 ns. The short pulse generation is based on the combination of a high-performance continuous laser source combined with a large bandwidth modulation.

The ModBox-OPG is a family of optical pulse generation units which generate pulses with durations from 30 ps to hundreds of nanoseconds, and with very high extinction ratio. The available optical shapes are Gaussian and square waveform. The ModBox works at any wavelength, and for an optical pulse train repetition which is externally triggered up to gigahertz repetition rates.

The optical spectral broadening ModBox-OSB achieves the broadening of an optical signal by modulating its phase via the mean of a very efficient LiNbO₃ phase modulator. A number of side bands are created over a spectral width that can reach several hundreds GHz. The ModBox-OSB contains a single-tone RF generator, white noise sources or PRBS sources. The ModBox-OSB integrates laser chain such as High Energy Lasers (HEL) lasers or Spectral Beam Combining laser architectures (SBC).

LEDlas

Introducing our cutting-edge LED-pumped EO Q-switched Nd:YAG laser, designed for high-performance applications. This laser offers exceptional stability, a long lifespan, and minimal maintenance requirements. With a peak power exceeding 9 MW and a convenient USB computer interface, it's ideal for a variety of applications, including LIBS, photoacoustic imaging, circuit trimming, fat-panel-display repair, and material processing.

Bright Solutions

Bright Solutions offers various Q-switched lasers:

Wedge – nanosecond Q-switched lasers for 266, 355, 532, 1064, 1570, 3100 nm (also multi-wavelength configurations), used e.g. for atmospheric LIDAR, monitoring, glass machining or lithography
Onda – compact monolithic nanosecond Q-switched lasers for 266, 355, 532 or 1064 nm, used e.g. for lens marking, plastic marking or intravolume glass marking
Sol – compact Q-switched lasers for 355, 532 or 1064 nm, up to 200 kHz, used e.g. for automotive fabrication, electronic machining, ID card writing and other industrial applications
Vento – sub-nanosecond MOPA lasers with pulse durations down to 500 ps, up to 200 kHz, up to 100 W average power at 1064 nm or 50 W at 532 nm, e.g. for LIDAR or PCB microprocessing
[Aero – high energy lasers ](aero-high-energy-dpss-lasers/) with up to 200 mJ at 1064 nm, 100 mJ at 532 nm, multi-wavelength configurations, custom beam shaping, application e.g. in atmospheric LIDAR, LIBS or nonlinear spectroscopy
ONE DPSS – miniaturized Q-switched lasers with up to 200 μJ and down to 3 ns, e.g. for atmospheric LIDAR and laser marking on plastics

Alpes Lasers

Alpes Lasers offers pulsed QCLs with wavelengths ranging from 4 to 14 μm and average powers up to hundreds of milliwatts. The unique nature of QCLs makes them perfectly suited for very short-pulse applications.

Teem Photonics

Teem Photonics offers air-cooled diode-pumped passively Q-switched lasers – pulsed Microchip and Powerchip lasers series, as well the PicoOne and PicoMega laser series, based on a MOFA architecture, i.e., using a fiber amplifier. All can generate intense sub-nanosecond pulses. Available emission wavelengths are 1064 nm, 532 nm, 355 nm, 266 nm and 213 nm.

Lumibird

Lumibird manufactures a wide range of nanosecond pulsed lasers thanks to its expertise in three key technologies: solid-state lasers, fiber lasers and fiber amplifiers, and laser diodes. Various application areas are addressed in industry (manufacturing, lidar sensors), science (laboratories and universities), medical (ophthalmology) and defense.

HÜBNER Photonics

HÜBNER Photonics offer pulsed nanosecond lasers in the Cobolt Tor Series: up to 0.5 mJ/pulse, <5 ns pulse width, 7 kHz pulse repetition rate with single pulse triggerable and free running models.

Stuttgart Instruments

The Stuttgart Instruments Primus is an ultrafast (fs) mode-locked oscillator, based on the solid-state technology. It provides a high average output power combined with a superior low noise level (shot noise limit above 300 kHz) and an excellent long-term stability.

The solid-state technology with 1040 nm central wavelength enables the excellent long-term stability by providing several watts of output power at 40 MHz pulse repetition rate and 450 fs pulse duration. Its superior low noise level reaches the shot noise limit above 300 kHz. In combination with the stability and output power, it enables ultrasensitive measurements and makes the Primus perfectly suited as pump source for frequency converters like the Stuttgart Instruments Alpha. The entire system is encapsulated in a solid CNC-cut and water-cooled housing, thus reaching excellent robustness against external perturbations.

NKT Photonics

NKT Photonics offers a variety of pulsed lasers, covering a wide spectral range from UV to visible and infrared. We have packaged the lasers in a sealed, robust enclosure allowing operation in harsh environmental conditions. They are air-cooled and maintenance-free. We offer femtosecond fiber lasers as well as a wide range of picosecond pulsed diode lasers.

CNI Laser

CNI offers nanosecond Q-switched lasers with wavelength coverage from 223 nm to 4800 nm. We have versions with pulse energies from 1 μJ to 10 J, repetition rates from 1 Hz to 200 kHz and pulse width from 0.8 ns to 200 ns. The lasers can be actively or passively cooled with air or water, or with conduction cooling, and there are various controls and outputs.

CNI also offers picosecond lasers.

Sacher Lasertechnik

Sacher Lasertechnik offers nanosecond pulsed diode lasers with emission wavelengths between 630 nm and 1650 nm, e.g. for time-resolved fluorescence spectroscopy.

Active Fiber Systems

AFS’s customized kW average power and multi-mJ pulse energy ultrafast laser systems are based on AFS leading-edge fiber technology. They unite multiple main-amplifier channels using coherent combination, a technology which AFS has matured to an industrial grade. All essential parameters are software-controlled and can be tuned over a wide range, making them an extremely valuable tool for numerous application.

ALPHALAS

ALPHALAS manufactures pulsed lasers with picosecond and nanosecond pulse durations that are targeted at material processing, micromachining, nonlinear optics, scientific research and various other applications which require high peak power or time resolved measurements. Advanced mode-locking and Q-switching techniques provide a huge variety of parameters for the laser pulses. Regeneratively amplified lasers with extremely high peak power in the megawatt range, picosecond pulse durations and up to mJ pulse energy are offered with various wavelengths, e.g. 914, 946, 1030, 1047, 1053, 1064, 1320 or 1342 nm and their second, third and fourth harmonics.

Educational laser kits with various modes of operation offer nanosecond or picosecond pulse durations.

Customer-specific designs for pulses larger than 100 ns or variable pulse durations are also available.

GWU-Lasertechnik

GWU-Lasertechnik has more than 30 years of experience in lasers and nonlinear optics. We are the pioneer of commercial BBO OPO technology. Our widely tunable laser sources cover the spectral range from the deep-UV at <190 nm to the IR at >2700 nm. We offer pulsed solutions for nano-, pico- and femtosecond pulses with best performance and highest reliability.

Monocrom

Monochrom offers different types of pulsed lasers:

Q-switched diode-pumped lasers such as the LQ-527-12: a frequency-doubled Nd:YLF laser emitting up to 1 mJ at 527 nm
pulsed high-power diode lasers with longer pulse durations but very high pulse energies, such as the HiEN Puls x5400-YAG

Leukos

LEUKOS offers the passively Q-switched laser HLX-I, a compact microchip laser generated sub-nanosecond pulsed at 1064 nm. Different versions are available, with up to 500 MW average output power and 50 μJ pulse energy. It is suitable for micromachining, a seed laser, for LIDAR, 3 D scanning and imaging, biophotonics, supercontinuum generation and in other fields.

See our data sheet.

Geola

Geola speciales in TEM₀₀ and SLM pulsed lasers from sub-ns pulse duration to >10 J per shot.

MPB Communications

MPBC’s line of pulsed fiber lasers are designed to address a range of market applications including medical and bio-medical research, semiconductor inspection, micro-machining, metrology, and multi-photon microscopy.

Products include:

Mode-locked ultrafast fiber lasers which operate at 515 nm, 532 nm, and anywhere from 920 nm to 1570 nm. They generate linearly polarized nearly transformed-limited pulses with pulse durations in the femtosecond or picosecond regime. With repetition rates in the range 10–100 MHz, and an average power of greater than 1.5 W, our ultrafast lasers are designed for a wide range of applications.
Sub-nanosecond pulsed fiber lasers, available from 514 nm to 1700 nm and with user-selectable repetition rates, are based on an all-fiber laser cavity, offering excellent beam quality and wall plug efficiency.

RPMC Lasers

Serving North America, RPMC Lasers offers versatile pulsed lasers from femtosecond to nanosecond, with single-shot to 200 MHz rep rates, adjustable PRR, and pulse widths. Delivering MW peak powers and nJ to 100s of mJ energies, they suit cold ablation, LIDAR, and more.

Spanning UV (210 nm) to mid-IR (4500 nm) with up to 5^th harmonics, plus tunable, narrow linewidth, and broadband options, they enable cost-effective solutions for spectroscopy, metrology, and every market.

Customizable platforms—from ultrafast fiber to ultra-low SWaP MIL-spec—offer tailored pulses, wavelengths, and rugged designs for industrial, medical, aerial, space, or lab use.

Let RPMC help you find the right pulsed laser today!

AdValue Photonics

AdValue Photonics offers different kinds of Q-switched nanosecond lasers, all emitting in the 2-μm spectral region (1950 nm):

The Q-switched laser module AP-QS1-MOD generates pulses with 20 ns to 200 ns duration, up to 30 kHz repetition rate, up to 10 W average output power and high beam quality. The module also has an output modulation capability.
The Q-switched laser AP-QS is a compact seed laser delivering 5-μJ pulses with up to 30 kHz repetition rate.
The Q-switched laser AP-QS1 with a rack housing offers up to 5 W average power and 250 μJ pulse energy.

Besides, AdValue Photonics has picosecond and femtosecond fiber lasers.

TOPTICA Photonics

TOPTICA's FemtoFiber lasers provide reliable femto-/picosecond pulses based on polarization-maintaining fibers and SAM mode-locking. Different models (1560/780 nm, VIS/NIR tunable output, IR/NIR supercontinuum, short-pulse) cover a wide range of applications, e.g. time-domain terahertz, microscopy, attoscience and as seed lasers.

Megawatt Lasers

MegaWatt Lasers Inc. offers CTH:YAG and Er:YAG resonators. These are flash lamp pumped and water cooled. They are optimized for energy and repetition rate. The CTH:YAG resonator is able to generate 4-J pulses at a repetition rate of 10 Hz, while the Er:YAG resonator reaches 3 J at also 10 Hz. Both allow for adjustable pulse widths.

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