Optical Modulators
Definition: devices allowing one to manipulate properties of light beams, such as the optical power or phase
German: optische Modulatoren
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, polarization 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.
- Electroabsorption modulators are intensity modulators, used e.g. for data transmitters in optical fiber communications.
- Interferometric modulators, e.g. Mach–Zehnder modulators, are often realized in photonic integrated circuits for optical data transmission.
- Fiber-optic modulators can exploit various physical principles. They can be true fiber devices, or contain fiber pig-tailed bulk components.
- Liquid crystal modulators are suitable for, e.g., optical displays and pulse shapers. They can serve as spatial light modulators, i.e. with a spatially varying transmission, e.g. for 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). Of course, that kind of device cannot provide arbitrary modulation controlled with an electrical input signal.
- Micromechanical modulators (which are microelectromechanical systems = MEMS), e.g. silicon-based light valves and two-dimensional mirror arrays, are particularly useful for projection displays.
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.
Suppliers
The RP Photonics Buyer's Guide contains 33 suppliers for optical modulators. Among them:

EKSMA OPTICS
We produce 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.
See us at Photonics. World of Lasers and Optics 2019 in Moscow, March 4–7 (booth 73A23) and Laser World of Photonics China 2019 in Shanghai, March 20–22 (booth W3.3610)!


Gooch & Housego
Acousto-optic multi-channel modulators (AOMC) allow multiple beams to be modulated or deflected independently by integrating an array of transducers with a single acousto-optic crystal. We have minimized crosstalk through proprietary optical and electrical designs to allow concurrent operation of up to 48 channels for modulation, and up to 8 channels for beam deflection. Our multi-channel modulators are known for their reliable operation and high performance.
Multi-channel modulators are most often used for high speed applications like micromachining and direct-write lithography, as each beam can be modulated independently. They are also used to increase throughput when writing large media by writing multiple beams at the same time.
See also: intensity modulators, phase modulators, acousto-optic modulators, electro-optic modulators, electroabsorption modulators, Pockels cells, Pockels cell drivers
and other articles in the categories lightwave communications, photonic devices
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