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在相干探测系统中,信号光与本振光在探测器上进行混频产生中频信号,实现将携带目标信息的信号光转置与放大,实现了近量子噪声限的探测方式。为了有效利用回波信号获得良好的探测性能,有必要对两束光的混频特性进行研究。信号光与本振光在探测器光敏面上的分布决定了两束光的混频效率,只有信号光与本振光的场分布完全一致探测器输出的中频光电流最大。通过对高斯光束的混频进行理论推导并进行数值模拟,结果表明混频效率对光敏面上信号光的分布较为敏感,本振光束腰半径应该等于或略大于信号光束腰的半径,探测器光敏面半径应约为本振光束腰半径的2倍。
In the coherent detection system, the signal light and the local light are mixed on the detector to generate the intermediate frequency signal, so that the signal light carrying the target information is transposed and amplified, and the detection method of the near quantum noise limit is realized. In order to effectively use the echo signal to obtain a good detection performance, it is necessary to study the mixing characteristics of the two beams. The distribution of the signal light and the local light on the photosensitive surface of the detector determines the mixing efficiency of the two beams, and only the field distribution of the signal light and the local light exactly matches the maximum output photocurrent of the detector. The theoretical derivation and numerical simulation of the Gaussian beam mixing results show that the mixing efficiency is sensitive to the distribution of signal light on the photosensitive surface. The local oscillator beam waist radius should be equal to or slightly larger than the signal beam waist radius. The detection The photosensitive surface radius should be about 2 times the local beam waist radius.