Abstract: -optic tunable filter (AOTF) is an electronically tuned optic filter that operates on the principle of acousto-optic diffraction. It consists of a birefringent crystal to which a piezoelectric transducer is bonded. The transducer converts the rf signal applied on it to acoustic wave, the acoustic wave launched into the crystal modulates the index of refraction of crystal periodically. This provides a moving phase grating which will diffract portions of incident light beam. For a fixed acoustic frequency, only a limited spectral band of incident light can approximately satisfy the phase-matching condition and be diffracted by the filter. The center of the band will change with the acoustic frequency, i.e., rf signal frequency. Thus a spectral filter is created. AOTF has advantages of wide tuning range, high spectral resolution, large angular aperture, and fast scan rate. These advantages make AOTF attractive for a variety of applications. !5
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