Crystal geometry measurement of an acousto-optic tunable filter using the tested tuning curves

A simple method of measuring the actual crystal geometry of an acousto-optic tunable filter (AOTF) was proposed. The relations between the tuning curves and the geometry were exactly analyzed for both incident polarizations. Through two optimization algorithms, the acoustic wave phase propagation angle and the incident facet angle were computed from the tested tuning curves successively. The exit wedge angle was measured similarly by swapping the incident and exit facets. A well fabricated 430 ~ 785 nm AOTF with known designed transducer cut angle 9.5° was chosen for experiment. The actual three angles were successfully measured. To verify this method, another experiment of measuring the non-diffracted light deflection angle was conducted. Its result highly approached the theoretical value calculated by the measured crystal geometry. This method is useful to establish the AOTF ray tracing model for optic design and to evaluate the AOTF performance by comparing with the designed geometry.