Research of pointing deviation of acousto-optic deflector due to ultrasonic attenuation

Acousto-optic interaction equations were established separately under two situations of without or with the consideration of ultrasonic attention and the angular distribution of ultrasonic power. The transfer function in spatial-frequency domain between the diffracted light and incident light was derived by employing spatial Fourier transform approach. Numerical simulation was performed. The results indicate that due to ultrasonic attenuation, the peak intensity of diffracted light deviates from the center of the beam and the distribution of diffracted light intensity is not Gaussian type any more, which leads to the pointing deviation of transmitting terminal in inter-satellite optical communications. The study of the dependence of the distribution of diffracted light intensity on ultrasonic power and ultrasonic frequency shows that the peak intensity deviation of the diffracted light can be eliminated when a certain value is chosen for the ultrasonic power. This certain value was defined as the optimal ultrasonic power P_opt. The relation between optimal ultrasonic power and ultrasonic frequency was given by applying a polynomial fitting to various P_opt in the whole bandwidth of acousto-optic deflector. The pointing deviation due to ultrasonic attenuation can be compensated by adjusting the ultrasonic frequency and ultrasonic power synchronously according to the expression of polynomial fitting.