High resolution noncollinear acoustooptic filters with variable passband characteristics: design

A generalized method for designing a high resolution acoustooptic filter with variable passband characteristics is described and experimentally verified in crystalline quartz. The optical passband of this filter configuration is made insensitive to acoustic divergence by canceling the wave vector mismatch caused by acoustic divergence by the similar effect introduced by the anisotropy of the acoustic velocity within the acceptance angle. About 0.4-nm half-power bandwidth with an external half-angular aperture of ~3° was obtained at 488 nm in a quartz filter. By changing the effective interaction length from 47 to 6 mm the passband was varied approximately from 0.4 to 3.5 nm. The possibilities of finding suitable filter orientations in Tl3AsSe3 and TeO2 are also discussed.