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A Brief Overview of Acousto-Optic Modulator

2017-02-28

Acousto-Optic ModulatorAcoustic-optic modulator (AOM), also termed a Bragg cell, is an efficient device which is used to control laser bean intensity by enabling intensity, frequency and direction of a laser beam to be modulated. It makes use of the acoustic-optic effect to separate and channel the frequency of the light by making use of sound waves generally at radio-frequency. This can be an uncomplicated ON:OFF modulation for rapid switching and/or variable level modulation to render relative control of the intensity. The alteration of the refractive index is by the oscillating mechanical pressure of a sound wave. These modes are ascertained with the help of the RF driver type – analog or digital modulation, or in some cases combination of both. The drive frequency of RF is usually fixed and the RF amplitude is regulated accordingly. According to research done on the acousto-optic modulator market, based on device it has been segmented into deflector, modulator, frequency shifter, tunable filter, mode locker, Q-switch, cavity dumper or pulse picker, and RF driver. Acousto-optics devices consists of several materials such as lithium niobate, tellurium dioxide, silica, arsenic trisulfide, lead silicate, tellurite glasses, and lead (II) bromide which display an acousto-optic effect. AOM is widely used in telecommunications for signal modulation, lasers for Q-switching, and in spectroscopy for frequency control. The prime element of an AOM is a transparent crystal with the help of which the light propagates. A piezoelectric transducer linked to a material like glass is utilized to stimulate a sound wave which has a frequency of the order of 100 MHz.

Significant Properties of Acousto-optic Modulators

Several prospects could be necessary for the selection of an acousto-optic modulator for some application:

 

  • In various cases, superior diffraction efficiency is vital. For instance, this is concerned when using the AOM as a Q-switch in a high-gain laser, and more so for dumping of cavity.
  • The material must possess greater transparency at pertinent wavelengths, and parasitical reflections ought to be reduced.
  • The switching time is significant for a few applications. This is controlled by fixed velocity of sound in the AOM. This entails that an AOM switching a laser bean along with greater diameter is inevitably low.
  • The needed power for the RF regulates both the cooling issues and electric power demands.
  • Superior optic peak powers need a well-suited material and a huge open aperture, enabling for a high damage threshold.
  • The device has to be used in broad range of RF frequencies for shifting frequencies.