准直透镜失调对Littman-Metcalf光栅外腔激光器线宽的影响

以光栅外腔半导体激光器的理论知识为基础，对Littman-Metcalf型外腔半导体激光器的工作原理进行了说明，并详细地讨论了外腔半导体激光器的线宽压窄以及模式选择机制，采用严格的耦合理论和光线变换矩阵推导了系统结构参数对光场耦合效率影响的计算公式。同时，对影响Littman-Metcalf外腔激光器输出激光线宽的几个重要因素进行了分析，重点讨论了系统中准直透镜位置失调导致的线宽变化规律。计算结果表明:合理地控制Littman-Metcalf光栅外腔半导体激光器的外腔参数可以将中心波长为785 nm半导体激光器的本征线宽压窄四个数量级，该外腔系统中准直透镜位置失调会影响系统出射光场与经外腔反馈光场之间的耦合效率，进而影响光栅外腔半导体激光器的输出线宽。

Influence of the misalignment of the collimating lens on the line-width of Littman-Metcalf grating external cavity laser

Based on the theoretical knowledge of grating external cavity semiconductor laser, the working principle of Littman-Metcalf type external cavity semiconductor laser was explained, and the wide voltage narrow ground wire and mode selection mechanism of external cavity semiconductor laser were discussed in detail. Based on strict coupling theory and ray transformation matrix, the calculation formula of the influence of system structure parameters on the coupling efficiency of light field was derived. At the same time, several important factors affecting the output linewidth of littman-Metcalf external cavity laser were analyzed, and the variation of linewidth caused by the misalignment of collimating lens in the system was discussed. The calculation results show that the proper control of the parameters of the littman-metcalf grating external cavity semiconductor laser can narrow the intrinsic linewidth of the semiconductor laser with the central wavelength of 785 nm by four orders of magnitude. In this external cavity system, the misalignment of the collimating lens would affect the coupling efficiency between the emitted light field and the feedback light field through the external cavity. Then the output linewidth of the grating external cavity semiconductor laser is affected.