激光诱导击穿光谱增强机制及技术研究进展

激光诱导击穿光谱技术是一种新的材料识别及定量分析技术。但是光谱的重复性低限制其由定性分析向定量分析的发展。因此提高激光诱导等离子光谱信号信噪比及等离子体的空间稳定性对于提高光谱信号的可重复性、降低基体效应等不利因素影响有着积极的作用。同时光谱信号信噪比的增强可降低对激光器输出能量的要求,有效降低了激光诱导击穿光谱集成系统的成本,有利于此技术向更多领域拓展。本文对实验中采用的双脉冲或多脉冲增强,放电脉冲再激发,空间限域,磁场束缚和微波辅助增强四大类方法加以总结及概括。在此基础上深入探讨光谱增强的物理机制,从而为进一步提高光谱信号稳定性及定量化分析的精确度提供有力的理论支持。     

A low noise,high fidelity cross phase modulation in multi-level atomic medium

We develop a hybrid scheme of cross phase modulation based on electromagnetically induced transparency (EIT) and active Raman gain (ARG) in a multi-level atomic medium. The cross phase modulation, with low loss and without noise, is demonstrated in a room-temperature ⁸⁵Rb vapor. We show that a π radian nonlinear Kerr phase shift of the signal light relative to a reference light is observed when the signal light is modulated by the phase control field with the low light intensity. We also show that the linear and the third-order absorption can be eliminated via the Raman gain, and the phase noise of the signal light can be ignored when the phase control light is applied in this hybrid scheme.