Effect of direction of incident light on the basic performance of a TeO₂ acousto-optic tunable filter.

The selection of the ultrasonic polar angle is vitally important to the performance of an acousto-optic tunable filter (AOTF). The effects of ultrasonic angle on various properties of AOTFs were studied. Then, according to the selected ultrasonic angle, the changes of internal and external separation angles were analyzed in detail when the light was incident upon the crystal surface in two different ways. Additionally, the drift of diffracted light caused by chromatic aberration was analyzed, and an appropriate compensation wedge angle was calculated by the improved derivation formula. The external separation angle increased obviously after placing a wedge angle on the output end. Finally, the effect of incident beam with a cone angle on spectral bandwidth and diffraction efficiency is discussed.