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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。
The 90 ° mixer plays an important role in achieving high sensitivity detection in spatially coherent laser communications. The relationship between signal light polarization and spatially coherent detection of mixing efficiency is studied. The circularly polarized light has better stability than the linearly polarized light used in the conventional scheme and is advantageous for high efficiency mixing. Therefore, a method of introducing 1/4 wave plate into the incident end of the signal to change the polarization state of the signal light is proposed. To simulate the signal light by the external factors affect the polarization state changes. The calculated signal power is used as a parameter to study the influence of signal polarization on the mixing efficiency. Assuming that the incident local oscillator light is the same and ignoring other constraints, it can be obtained that the maximum relative signal power is obtained when the mixer receives circularly polarized signal light, ie, the highest mixing efficiency.