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Optical Modulators

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

Definition: devices allowing one to manipulate properties of light beams, such as the optical power or phase

More specific terms: acousto-optic modulators, electro-optic modulators, Pockels cells, electroabsorption modulators, liquid crystal modulators, intensity modulators, phase modulators

Categories: article belongs to category photonic devices photonic devices, article belongs to category lightwave communications lightwave communications

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DOI: 10.61835/6t6 Cite the article: BibTex plain text HTML Link to this page! LinkedIn

An optical modulator is a device which can be used for manipulating a property of light – often of an optical beam, e.g. a laser beam. Depending on which property of light is controlled, modulators are called intensity modulators, phase modulators, modulators, spatial light modulators, etc.

A wide range of optical modulators are used in very different application areas, such as in optical fiber communications, displays, for active Q switching or mode locking of lasers, and in optical metrology.

Types of Optical Modulators

There are very different kinds of optical modulators:

Acousto-optic modulators are based on the acousto-optic effect. They are used for switching or continuously adjusting the amplitude of a laser beam, for shifting its optical frequency, or its spatial direction.
Electro-optic modulators exploit the electro-optic effect in a Pockels cell. They can be used for modifying the polarization, phase or power of a beam, or for pulse picking in the context of ultrashort pulse amplifiers.
Plasmonic modulators are a special type of electro-optic modulators which exploit the formation of plasmons (a special type of electromagnetic excitation) at metal surfaces, which lead to surface plasmon polaritons (SPPs). They can be extremely fast while having a low energy consumption.
Electroabsorption modulators are semiconductor-based intensity modulators, used e.g. for data transmitters in optical fiber communications.
Interferometric modulators, e.g. Mach–Zehnder modulators, are mostly exploiting the electro-optic effect in conjunction with interference. They are often realized in photonic integrated circuits for optical data transmission.
Liquid crystal modulators are suitable for, e.g., optical displays and ultrafast pulse shapers. They are also available as spatial light modulators, i.e. with a spatially varying transmission, e.g. for displays.
Micromechanical modulators (which are microelectromechanical systems = MEMS), e.g. silicon-based light valves and two-dimensional mirror arrays, are particularly useful for projection displays.
Chopper wheels can periodically switch the optical power of a light beam, as required for certain optical measurements (e.g. those using a lock-in amplifier), and may thus be considered as optical modulators in a wider sense. Of course, that kind of device cannot provide arbitrary modulation controlled with an electrical input signal.

Bulk-optical modulators, e.g. of the electro-optic type, can be used with large beam areas, and handle correspondingly large optical powers. On the other hand, there are fiber-coupled modulators, often realized as a waveguide modulator with fiber pigtails, which can easily be integrated into fiber-optic systems.

More to Learn

Intensity modulators

Phase modulators

Acousto-optic modulators

Electro-optic modulators

Electroabsorption modulators

Liquid crystal modulators

Pockels cells

Pockels cell drivers

Optical choppers

Suppliers

The RP Photonics Buyer's Guide contains 65 suppliers for optical modulators. Among them:

Exail

Exail (formerly iXblue) offers the most comprehensive range of commercial LiNbO₃ modulators:

the MXER-LN series of intensity modulators for the C and O bands
the MPZ-LN phase modulators for the C and O bands
the near-infrared phase modulators NIR-MPX for the region around 1064 nm
the NIR-MX Mach–Zehnder modulator for the 1-μm spectral region
the xx-MPX-LN-0.1 series for wavelengths between 780 nm and 2000 nm and low modulation frequencies
the MZ-LN family for 1310 nm to 1550 nm with a modulation bandwidth up to 70 GHz
the space-qualified FM-MX and FM-MPX series
the PSW-LN and PSC-LN polarization switches and scramblers

In addition, we offer suitable bias controllers, analog and digital drivers. We also have pulse drivers for generating and shaping pulses.

See our comprehensive brochure on modulators.

Thorlabs

With the introduction of the OM6N series of high-speed optical modulators, Thorlabs has designed and developed a new all-reflective technology based on deformable mirrors for modulating laser power in the 700 – 1350 nm range. This Pockels cell or AOM alternative introduces nearly zero dispersion to ultrafast laser pulses.

Shalom EO

Hangzhou Shalom EO offers off-the-shelf and custom Pockels cells, we can provide off-the-shelf and customized BBO, DKDP, LiNbO₃ and MgO:LiNbO₃ Pockels cells for electro-optical modulation.

The DKDP Pockels cells are of the longitudinal type. They feature high deuteration (>98%), fast rise time, and a maximum aperture of 50 mm.
The BBO Pockels cells are the best choice for high reptition rate Q-switching, with the additional advantages of high damage threshold and low insertion loss.
The LiNbO₃ and MgO:LiNbO₃ Pockels cells are of the transverse type. They have large electro-optic coefficients, good transmission up to 4.0 µm, and low half wave voltage. Aperture sizes of 2.5 mm to 9 mm are available.

In addition, we also provide RTP Q-switches, and electro-optical and acoustic-optical crystals (BBO, DKDP, LiNbO₃ / MgO:LiNbO₃, TeO₂) which are the core elements used in optical modulators and Pockels cells.

EKSMA OPTICS

EKSMA Optics produces KTP, KD^*P and BBO Pockels cells for applications like Q-switching of lasers, pulse picking, laser cavity dumping and coupling laser pulses into and from regenerative amplifiers. Our Pockels cells can be supplied with mounting stages, drivers, power supplies and electronics for pulse picking.

AeroDIODE

AeroDIODE has developed the fiber modulator – a high-speed intensity modulator and optical switch based on a semiconductor optical amplifier (SOA). It is available over a wide wavelength range from 750 to 1650 nm. Key features are high speed (down to 1 ns rise/fall time), high dynamic range (>48 dB), high extinction ratio (>50 dB) and an easy to use graphical user interface with multiple software libraries (LabVIEW, Python etc.). AeroDIODE also offers the Semiconductor Optical Amplifier alone or the SOA driver in either CW or pulsed configuration.

AeroDIODE also offers a wide range of fiber coupled AOMs (Acousto Optic Modulators) with various types of digital (TTL) or analog RF drivers.

ALPHALAS

Phase and amplitude electro-optical as well as acousto-optical modulators in a standard and customer-specific configuration, including the drivers are available on order from ALPHALAS. Standard wavelengths are 1030 nm and 1064 nm, but customized wavelengths can also be supplied.

GWU-Lasertechnik

GWU's assortment covers acousto-optic (AOM) and electro-optical (EOM) modulators (the latter based on BBO or KD^*P). All components can be offered free-space or fiber coupled and with suitable driver electronics.

Raicol Crystals

Raicol Crystals offers electro-optic modulators based on RTP (with a temperature compensating design) or BBO.

Besides, we can supply super-polished LBO crystals which can be used as the center piece of an electro-optic modulator. With its high resistance to laser-induced damage, LBO is very suitable for high-power applications, and its transparency range is large (160 nm – 2600 nm). We offer highly homogeneous crystals with up to 100 × 100 mm² and very low bulk absorption.

Quantifi Photonics

Quantifi Photonics' IQTX coherent modulation transmitter generates and controls phase-modulated optical signals at 11 GHz, 20 GHz, 23 GHz or 40 GHz of bandwidth. It supports M-QAM, M-PSK and custom modulation formats and Baud rates beyond 64 GBaud.

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