高斯光束与谐振腔基模模式光路谐振匹配的分析与校准

Analysis and alignment of the light path of Gauss beam matched to the fundamental mode of an optical resonator

为了降低高斯光束与谐振腔耦合过程中失调量和失配量对基于无源谐振腔测量技术精度的影响,采用高斯光束变换规律、模式耦合有关理论以及光束传播坐标变换等相关理论,就失调量和失配量对基模耦合效率的影响分别进行分析和模拟,并据此给出了一般情况下两个参考量同时存在时基模耦合效率的表达式.分析表明:失配量的存在主要影响激光器与谐振腔的耦合效率,而对高阶模式的激发影响较小,因此对谐振腔的衰减线型影响较小;失调量的存在对谐振腔高阶模式的激发起主要作用,给测量带来严重误差.该结论为利用腔出射光信号来确定误调参量值的实验方案提供了依据.因此,在考虑光源光谱线宽的情况下,就光源光谱线宽的特性提出两种装调校准方案:基于法布里-珀罗干涉仪法和基于多维象限探测器探测谐振腔出射光的调节回路,这将为分析基于无源谐振腔的相关技术测量误差来源以及实现测量系统的高精度装调提供理论指导.

In order to reduce the influences of misalignment parameter and mismatch parameter on measurement based on optical resonator, the influence on the coupling efficiency of a source laser is stabilized to a fundamental cavity mode, and two limiting cases are analyzed and derived by using conversion of Gaussian beam, mode coupling theory and coordinate transformation theory, including the expression of coupling efficiency of fundamental cavity mode as two limiting cases emerge simultaneously. Analyses show that for mismatch parameter, only even-indexed Hermite-Gaussians beam is excited; for misalignment parameter, there exists an effect on the proportion of Hermite-Gaussians beam, which should bring about serious measurement error. These optical signals provide the error signals which are minimized. By taking the laser line width into account, we propose two methods for real time alignment of a Gaussian beam for an optical resonator perfectly coupled system： Fabry-Perot electro-optic sensors of a misadjusted system and control loops system depends on detecting emergent light of cavity via multi-dimensional quadrant detector. All of these will provide a theoretical direction for analyzing the measurement error and improving the measurement accuracy.