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An acousto-optic modulator (AOM), also called a Bragg cell or an acousto-optic deflector (AOD), uses the acousto-optic effect to diffract and shift the frequency of light using sound waves (usually at radio-frequency). They are used in lasers for Q-switching, telecommunications for signal modulation, and in spectroscopy for frequency
Acousto-optic modulators are used to vary and control laser beam intensity. A Bragg configuration gives a single first order output beam, whose intensity is directly linked to the power of RF control signal. The rise time of the modulator is simply deduced by the necessary time for the acoustic wave to travel through the laser beam.
An acousto-optic modulator. By varying the parameters of the acoustic wave, including the amplitude, phase, frequency and polarization, properties of the optical wave may be modulated. The acousto-optic interaction also makes it possible to modulate the optical beam by both temporal and spatial modulation.
The refractive modulators are named by the respective effect: i.e. electrooptic modulators, acousto-optic modulators etc. The effect of a refractive modulator of any of the types mentioned above is to change the phase of a light beam. The phase modulation can be converted into amplitude modulation using an interferometer or directional coupler.
An acousto-optical spectrometer (AOS) is based on the diffraction of light by ultrasonic waves. [1] A piezoelectric transducer, driven by the RF signal (from the receiver), generates an acoustic wave in a crystal (the so-called Bragg-cell). This acoustic wave modulates the refractive index and induces a phase grating.
An acousto-optic programmable dispersive filter (AOPDF) is a special type of collinear-beam acousto-optic modulator [1] capable of shaping spectral phase and amplitude of ultrashort laser pulses. AOPDF was invented by Pierre Tournois . [ 2 ]
Related to this amplitude modulation (AM), active mode locking is frequency-modulation (FM) mode locking, which uses a modulator device based on the acousto-optic effect. This device, when placed in a laser cavity and driven with an electrical signal, induces a small, sinusoidally varying frequency shift in the light passing through it.
An acousto-optic deflector (AOD) is a device that uses the interaction between sound waves and light waves to deflect or redirect a laser beam. AODs are essentially the same as acousto-optic modulators (AOMs). In both an AOM and an AOD, the amplitude and frequency of different orders are adjusted as light is diffracted.