Abstract

Acousto-optic tunable filters (AOTFs) are electronically addressable optical filters that provide rapid, random wavelength access, broad spectral coverage and moderately high spectral resolution. They are based on acousto-optic diffraction of light in an anisotropic medium. A piezoelectric transducer bonded to a birefringent crystal generates a traveling acoustic wave through the crystal, whenever it is excited by an applied RF signal. This acoustic wave establishes a periodic modulation of the index of refraction and generates a moving grating which allows diffraction of the incident light beam. For a given acousto-optic frequency, only a small wavelength band will satisfy the phase-matching condition and will be cumulatively diffracted. Varying the RF frequency has the resulting effect of changing the center of the optical bandpass. In addition, applying multiple RF frequencies simultaneously, result in multiple wavelength bandpasses.

© 1996 Optical Society of America