外差探测系统的相位匹配研究

Phase Matching of a Heterodyne Detection System

从外差探测系统设计的基本要求出发.分析本振光与信号光的相位匹配技术.表明当目标回波聚焦像斑与本振光聚焦腰斑不重合时,像斑大小直接影响信号幅度,波长越短,相位匹配越困难.系统发射的探测光束发散角较大时,信噪比较差,且光束扫过点目标可能出现条纹状信号过程.分析所得主要结论得到了实验验证.

The phase matching technique between the signal and the local oscillator (LO) wave is analysed according to demands for the heterodyne detection system design. It shows that the focused signal wave speckle size dominates the output SNR when it doesn't coincide with the focused LO beam waist, and the phase matching becomes more difficult for the shorter wavelength. For large probe beam divergence the SNR is relatively poor, and even a streaky signal process is predicted if a point target is scanned across. The major conclusions from the analysis above are verified by an experiment.