90°混频器对空间相干激光通信中实现高灵敏度探测起着重要作用。研究了信号光偏振态与空间相干探测混频效率的关系。圆偏振光比传统方案所用的线偏振光具有更好的稳定性, 且有利于实现高效率混频, 因此提出了在信号入射端引入1/4波片的方法来改变信号光的偏振态, 以模拟信号光受到外界因素影响时的偏振态变化情况。将计算得到的信号功率作为参量, 研究信号光偏振态对混频效率的影响。假定入射本振光相同且忽略其他限定条件, 可以得到: 混频器在接收圆偏振态信号光时, 可获得最大的相对信号功率, 即混频效率最高。

A 90° mixer plays an important role in achieving a high sensitivity detection in space coherent laser communication. The relationship between signal light polarization state and mixing efficiency of space coherent detection is studied. The circularly polarized light is more stable than the linearly polarized light used in traditional programs, and it is beneficial to achieving a high efficient mixing. A method that a 1/4 wave plate is introduced at the signal input end is proposed to change the polarization state of the signal light, and the simulation for the change of signal light polarization state is carried out when the signal light is influenced by external factors. The calculated signal power is used as a parameter, and the influence of the signal light polarization state on the mixing efficiency is studied. When incident local oscillator lights are same and other limited conditions are ignored, we come to a conclusion that the maximum relative signal power can be obtained by the mixer when the mixer receives circularly polarized signal light, and its mixing efficiency is the highest.