直角内圆锥面全反射镜激光谐振腔模式的数值模拟

Numerical Simulation of an Optical Resonator with a 90° Cone Reflector

直角内圆锥面全反射镜激光谐振腔由于其特殊的结构,从而具有较好的抗失调特性。选择高功率横流CO2激光器作为数值模拟的模型,采用Fox-Li迭代法对此种谐振腔的输出光束模式进行了分析。当光束在直角内圆锥面全反射镜处发生翻转时,进行了简化计算。由于直角内圆锥面全反射镜会干扰光束的偏振态,所以采用一种矢量分析的方式对输出光束的模式进行了分析。研究发现当选取P光和S光的反射率相差超过3%时,此种谐振腔可得到偏振纯度为1的径向偏振光或角向偏振光。

An optical resonator with a 90° cone reflector has a better misalignment tolerance because of its special structure. In this paper, a high-power transverse flow CO2 laser is selected as a model for numerical simulation, and the Fox-Li iterative approach has been used to analyze the output beam mode of the laser resonator. Calculation process is simplified when the beam transformation occur at 90° cone reflector. Because a 90° cone reflector is a no-paraxial device, and linear polarization is not preserved by the reflection. A modified vector method is used to analyze mode distribution of the output beam, and the results show that when the reflectivity difference between P and S polarizations is more than 3%, the radially polarized or azimuthally polarized beam with a polarization purity of 1 can be obtained by such resonator.