硅拉曼激光器的设计与典型应用

Design and typical application of silicon Raman laser

针对用光腔衰荡法测量气体浓度时存在严重非线性光学损耗,输出功率密度偏低,光源输出不平坦等问题,利用受激拉曼散射(SRS)非线性频移机制,设计了以Si元素作为拉曼主要增益介质的拉曼激光器。在硅波导结构中设置了p-i-n反向偏置电压,通过控制调节该电压值来降低由双光子吸收(TPA)引起的自由载流子吸收(FCA)以及由FCA引起的非线性光学损耗,从而提高拉曼激光器的输出功率。在实验分析处理过程中,将反向电压分别设置为开路、短路、5V以及25V4种状态,分析比较了不同电压值下激光器输出功率的变化规律。实验结果显示:粒子自由迁移时间从16ns降低到1ns,表明输出功率在同等标准下得以显著提高,进而改善了气体浓度测量的稳定性。

For the serious nonlinear optical loss,low output power density and non-flat light source in gas concentration measurement by a Cavity Ring-down Spectroscope（CRDS）,a Raman laser by using Si as gain media was designed based on the nonlinear frequency shift mechanism of stimulated Raman scattering.To reduce the Two-photon Absorption（TPA） induced Free-carrier Absorption（FCA） and the FCA induced nonlinear optical loss in the silicon,a reversed p-i-n diode was designed to embed in a silicon waveguide.Then,the output power of Raman laser could be enhanced by controlling the voltage.In the experimental analysis,the reversed voltage was set to open,short,5V and 25V,respectively,to observe the output power under the different voltages.The result indicates that the free carrier mobility time decreases from 16 ns to 1 ns and the output power increases outstandingly at the same condition,which enhances the reliability of gas concentration measurement.