Acousto-Optic Tunable Filter*

Abstract

This paper proposes a new type of electronically tunable optical filter. The basic idea is to utilize collinear acousto-optic diffraction in an optically anisotropic media. Changing the driving acoustic frequency changes the band of optical frequencies that the filter passes. A LiNbO3 acousto-optic filter with a pass band approximately 1.3 cm−1 wide should be tunable from 4000 to 7000 Å by changing the acoustic frequency from 428 to 990 Mc/sec. For this case, the angular aperture will be about 1.5°, and, theoretically 100% transmittance should be attained at the filter center frequency by use of about 14 mW of acoustic power per mm2 of filter aperture.