用大芯径石英玻璃光纤传输兆瓦级高能激光脉冲及其在双波长LA-LIBS技术中的应用  

Delivery of Megawatts High Energy Laser Pulse with Large Core Diameter Silica Fiber and Its Application in Dual-Wavelength Laser-Ablation Laser-Induced Breakdown Spectroscopy

作　　者：周奇[1] 彭飞飞[1] 李润华[1] 陈钰琦[1] 杨雪娇[1] 

机构地区：[1]华南理工大学理学院物理系,广东广州510641

出　　处：《光谱学与光谱分析》2013年第12期3392-3395,共4页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金项目(11274123);国家重大基础研究计划(973)项目(2012CB921900);华南理工大学中央高校科研业务费(x21x-D2116740)资助

摘　　要：为了解决单脉冲激光诱导击穿光谱(LIBS)技术在元素分析时空间分辨本领与分析灵敏度之间的矛盾,本文利用一台双波长输出的Nd:YAG激光器开展了双波长激光剥离-激光诱导击穿光谱(LA-LIBS)技术的研究。其中532 nm的二倍频激光用于剥离样品;1 064 nm的基频激光通过大芯径石英玻璃光纤传输并实现一定的延时后用于击穿被剥离的样品。两束激光采用正交几何配置以实现高空间分辨高灵敏的元素分析。实验研究了1 064 nm激光到光纤的耦合、光纤输出后的准直以及再聚焦时的一些关键技术问题。研究并得出了四种不同光纤对激光能量的传输能力。选择利用芯径为800μm,数值孔径为0.39、长50 m的石英玻璃光纤成功传输了15 mJ的调Q激光脉冲并实现了250 ns的延时。并在此基础上开展了铜合金样品的双波长LA-LIBS分析,实验验证了基于一台Nd:YAG激光器开展双波长LA-LIBS研究的可行性。该技术只需要一台激光器就可以完成相应的光谱分析,具有系统结构简单,便于小型化等优点,适合对不同样品开展原位的高空间分辨高灵敏的元素显微分析。To resolve the contradiction between spatial resolution and analysis sensitivity in single pulse laser-induced breakdown spectroscopy （LIBS）, a study on dual-wavelength laser-ablation laser-induced breakdown spectroscopy （LA-LIBS） was carried out by using one Nd ： YAG laser which was capable of two laser beam outputs with different wavelengths, where, the second harmonic output, 532 nm laser beam, was used as laser-ablation source, and the fundamental output, 1 064 nm laser beam, was delivered with a large core diameter silica fiber to realize nanoseconds time-delay and then used to breakdown the ablated sam- ples. Two laser beams were orthogonally arranged to realize element analysis with high spatial resolution and high sensitivity. Some key techniques on the coupling of I 064 nm laser beam into fiber, the collimation of laser at the fiber end and re-focusing of the laser beam were studied. The energy delivery capabilities of four fibers of different types were studied and the maximum val- ues were determined experimentally. A Q-switched laser pulse with 15 mJ pulse energy was successfully delivered by selecting a 50 meter long silica fiber with 800/lm core diameter and 0. 39 numerical aperture. And 250 ns time-delay was realized. A copper alloy was analyzed by spectra with current established LA-LIBS system and the possibility of realizing dual-wavelength LA-LIBS analysis based on one Nd ： YAG laser was demonstrated experimentally. In this technique, only one Nd ： YAG laser was re- quired to carry out spectral analysis. It has a few advantages, such as simple equipment structure, and being convenient to minia- turize the whole system etc. This dual-wavelength LA-LIBS technique was suitable for in-situ elements microanalysis for differ- ent samples with both high spatial resolution and high sensitivity.

关 键 词：光纤传能 激光剥离-激光诱导击穿光谱 高空间分辨 元素分析 

分 类 号：O433.4[机械工程—光学工程]