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分别在不考虑晶体超声吸收及考虑超声吸收和超声功率角分布的情况下,建立了声光互作用方程。运用空间傅里叶变换方法推导出衍射光场与入射光场在空频域下的传递函数。仿真结果表明,超声吸收使得衍射光光强峰值位置偏离光束中心,光强不再呈高斯分布,会引起卫星光通信发射端的指向偏差。通过研究超声功率和频率与衍射光光强分布的关系发现,超声功率选取某一数值时可以消除峰值位置偏差,将此功率值定义为最优超声功率Popt。求出声光偏转器整个工作频带内的Popt并进行多项式拟合,得到了最优超声功率与超声频率的关系。按照该多项式关系同步调节超声频率与功率可以补偿超声吸收引起的指向偏差。
The equations of acousto-optic interaction were established without considering the ultrasonic absorption of the crystal and taking into account the ultrasonic absorption and the angular distribution of ultrasonic power, respectively. The transfer function of the diffracted light field and the incident light field in the space-frequency domain is derived by using the method of spatial Fourier transform. The simulation results show that ultrasonic absorption makes the peak position of the diffracted light deviate from the center of the beam, and the light intensity no longer shows a Gaussian distribution, which causes the pointing deviation of the satellite optical communication transmitter. By studying the relationship between the ultrasonic power and the frequency and the light intensity distribution of the diffracted light, it is found that the peak position deviation can be eliminated by selecting a certain value of the ultrasonic power, and the power value is defined as the optimal ultrasonic power Popt. The Popt in the entire working frequency band of the acousto-optic deflector is obtained and polynomial fitting is performed, and the relationship between the optimal ultrasonic power and the ultrasonic frequency is obtained. Adjusting the ultrasonic frequency and power synchronously according to the polynomial relationship can compensate for the directional deviation caused by ultrasonic absorption.