Acoustooptical Tunable Filter -- from Eric Weisstein's World of Physics

Also called a Bragg cell. A prismatic crystal of , , , , , or GaP (Berg and Lee 1983, p. 50) in which standing acoustic waves are set up. The acoustic waves produce index of refraction changes, so the crystal essentially becomes a diffraction grating with the spacing set by the distance between wave peaks. By shining a laser through the crystal, a diffraction pattern is obtained, and the original signal may be obtained using Fourier methods.

Acoustooptical tunable filters can replace radio/infrared filter banks by adding a piezoelectric transducer at one end of the cell to convert a downmixed radio signal into an acoustic vibration. Acoustooptical filters are completely tunable.

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