不同激光参数下水下固体靶激光诱导击穿光谱实验研究  

Experimental Investigation of Laser-Induced Breakdown Spectroscopy on Submerged Solid Target Under Different Laser Parameters

作　　者：翟灿旭 田野[1] 叶旺全 卢渊[1] 郑荣儿[1] Zhai Canxu;Tian Ye;Ye Wangquan;Lu Yuan;Zheng Ronger(College of Physics and Optoelectronic Engineering,Faculty of Information Science and Engineering,Ocean University of China,Qingdao 266100,Shandong,China)

机构地区：[1]中国海洋大学信息科学与工程学部物理与光电工程学院,山东青岛266100

出　　处：《光学学报》2025年第1期303-309,共7页Acta Optica Sinica

基　　金：国家重点研发计划青年科学家项目(2023YFC2811700);国家自然科学基金面上项目(12174359);山东省自然科学基金优秀青年基金(ZR2023YQ059)。

摘　　要：激光脉宽与能量是影响水下激光诱导击穿光谱(LIBS)质量的关键因素。搭建一套水下固体靶LIBS探测系统,采集不同激光脉冲条件下水下铝靶的LIBS,分析激光脉宽为6~25 ns、激光能量为8~25 mJ的条件下光谱信噪比、信背比、相对标准偏差(RSD)以及其他物理特征的变化规律。结果表明:当激光脉宽大于12 ns时,随着激光能量的增加,信噪比逐渐增加,激光脉宽的增加能够显著提升信背比;当激光能量在16 mJ左右且脉宽大于14 ns时,光谱的稳定性较好。当激光峰值功率密度大于或接近水体击穿阈值时,光谱信号质量较差,从阴影图像与烧蚀坑的结果可知,在该条件下会出现多点击穿现象,空化气泡半径、冲击波速度与激光烧蚀量均较17 ns激光脉冲更大,激光能量转化为光谱辐射的效率低,因此LIBS信号质量大幅下降。由此得出,在激光峰值功率密度不超过水体击穿阈值且能击穿靶面的前提下,激光脉宽的增加能够有效改善水下LIBS信号。Objective Laser-induced breakdown spectroscopy(LIBS)technology has enormous potential for deep-sea in-situ detection due to its real-time,non-contact advantages.However,the high density and incompressibility of water result in underwater laser-induced plasma with high particle number density and low temperature,causing lower intensity and poor stability compared to gas environments.To improve the underwater detection capabilities of LIBS,using long-duration lasers can significantly enhance the emission line intensity,as proven by many studies.This improvement also positively influences the signal-to-noise ratio(SNR)and signal-to-background ratio(SBR)of LIBS signals.In this study,we analyze the LIBS signal quality generated on a submerged aluminum target,including line intensity,SNR,SBR,and relative standard deviation(RSD),under different laser durations(6?25 ns)and energies(8?25 m J).This provides an experimental basis for optimizing laser parameters in underwater LIBS.Methods A Q-switched Nd∶YAG laser with a wavelength of 1064 nm is used as the ablation source.The laser operates at pulse durations of 6 ns to 25 ns by varying the laser flash-pump voltage,with a repetition rate of 0.2 Hz.The laser passes through a half-wave plate and a Glan prism to adjust the laser pulse energy from 8 m J to 25 m J,monitored by a photodiode connected to an oscilloscope.A dichroic mirror transmits the laser beam and reflects the plasma emission light.Then the laser beam is focused into a quartz cuvette filled with deionized water by a pair of quartz plano-convex lenses L1(f=38.1 mm).The cuvette(80 mm×80 mm×80 mm)has a wall thickness of 2 mm.The target is mounted on an X-Y-Z stage and submerged in water,with the laser focal position set at 0.75 mm below the target surface.The diameter of the laser spot on the target surface is about 250μm,based on the measured crater size.Pure metals of aluminum(99.9%)are used,polished,and cleaned with alcohol before experiments.A water pump refreshes the water in the cuvette to reduce the int

关 键 词：激光诱导击穿光谱 激光脉宽 激光能量 水下固体靶 

分 类 号：O433.4[机械工程—光学工程]