摘要：
According to the effect of sound field distribution in an acousto-optic crystal on diffraction efficiency and optical fields, an apodization method was proposed to improve the laser heterodyne in-terferometric efficiency. By taking a TeO2 for a substrate, the effect of sound field distribution and volume grating contrast in an acousto-optic device on the diffraction efficiency was analyzed. A nonu-niform contrast model was established and the apodization method was used to control the nonuniform distribution of the spatial sound field. The results show that when the radio frequency is tuned to a working range from 100 to 105 MHz for an Acoustic Optical Modulation(AOM) without apodization, the diffractive spot shows two peaks with nonuniform distribution, diffractive light contains crosstalks with much noise and diffraction efficiency is affected. The heterodyne signal power is -1. 7 dBm. However, the apodization achieves a better diffraction efficiency and crosstalk suppression. The diffraction efficiency reaches the maximum 98%, transmission bandwidth has been 50% to 60% of thetotal diffraction bandwidth. The heterodyne signal power is 3. 8 dBm. The measurement results indicate that the method can optimize transmission capacity, suppress the crosstalk and can improve the laser heterodyne interferometric efficiency by an IF heterodyne signal voltage gain of 11 dB.%针对声光晶体内部的声波反射使晶体内声场分布不均匀,影响衍射效率和衍射光场分布,降低激光外差干涉效率的现象,以不改变声光设备为前提提出了光切趾方法.以TeO2晶体为基底,理论分析声光器件的声场分布、体光栅衬度及其对衍射光效率的影响.提出非均匀光栅衬度模型,并利用光切趾法控制空间声场非均匀分布.通过理论仿真结合实验测量,证明该方法的传输性能.实验结果表明:当射频满足器件工作中心频率在100～105 MHz时,使用切趾法前,衍射光斑呈现双峰,光强未均匀分布,其光斑中心不呈现光强极大值,衍射光束出现串扰并携带大量噪声,外差信号功率为-1.7 dBm;使用切趾法后,声场非均匀现象对光束质量的影响得到改善,光强分布均匀且呈高斯结构,声场衍射效率提高到98％,传输带宽达到总衍射带宽的50％～60％,外差信号功率达到3.8 dBm.结果表明:该方法在优化传输容量、抑制光串扰同时,可提高激光外差干涉效率,使外差中频信号电压增益为11 dB.
