Analysis of the optical and acoustic beam's incident angles for TeO₂ tunable filters

On the basis of TeO₂ acousto-optic tunable filters (AOTF) working principles and the requirements of the performance of the optical add/drop multiplexer (OADM) in optical communication, the choice of the incident angles of the optical and acoustic beams of the TeO₂ acousto-optic tunable filters is considered from the four aspects of the momentum-match, the optical rotation, the bandwidth and the collinear beam with Matlab program. The conclusions are that an optical incident angle works in the range of 4°-25° and 60°-90° in consideration of the optical rotation; and in order to make bandwidth smaller than 1 nm within the tunable range of 400 nm, it should be larger than 31° at least, otherwise the tuning range comes down; and it is necessary for the devices in optical communication to choose the non-collinear working mode when the momentum-match of the two incident angles is satisfied at first.