基于折叠近共心腔的拉曼光谱气体探测方法研究  

Raman Spectroscopy for Gas Detection Using a Folded Near-Concentric Cavity

作　　者：刘庆省 杨德旺 郭金家[1] 燕傲霜 郑荣儿[1] LIU Qing-sheng;YANG De-wang;GUO Jin-jia;YAN Ao-shuang;ZHENG Rong-er(College of Information Science and Engineering,Ocean University of China,Qingdao 266100,China;Laser Research Institute,Qilu University of Technology(Shandong Academy of Sciences),Qingdao 266100,China)

机构地区：[1]中国海洋大学信息科学与工程学院,山东青岛266100 [2]齐鲁工业大学(山东省科学院)激光研究所,山东青岛266100

出　　处：《光谱学与光谱分析》2020年第11期3390-3393,共4页Spectroscopy and Spectral Analysis

基　　金：山东省重点研发计划项目(2019JZZY010417);国家自然科学基金项目(61575181)资助。

摘　　要：拉曼光谱技术以多组分同时探测、无需样品预处理等优势被用于多个领域,但是较低的探测灵敏度制约了其更广泛的应用。为了提高拉曼光谱技术气体探测的灵敏度,文章报道了一种基于折叠近共心腔对气体拉曼信号进行增强的方法。该方法通过向多次反射腔中心引入一片高反射率平面镜将腔体从中心处进行折叠,使腔体中心处光束相互重叠以增加光线密度和光通量,进而提高系统的探测灵敏度。采用TracePro软件对不同模式下的多次反射腔进行光线追迹和通量分析(激光:300 mW@532 nm,镜面反射率:99%@532 nm),结果表明光腔折叠方式能够显著提高反射腔中心处的光通量。折叠近共心腔在反射次数为68次的情况下,光腰中心处光通量可达22.35 W,约为近共心反射腔光通量的1.5倍左右。进一步搭建了多次反射腔对模拟结果进行验证,实验结果表明:折叠近共心腔对拉曼信号信噪比增强效果最好,约为49倍;近共心腔次之为36倍;是折叠共心腔为24倍;最后是共心腔为17倍。与未折叠的近共心腔相比,采用折叠近共心腔采集的气体拉曼信号信噪比提高了约1.4倍。根据该系统探测到的空气中的二氧化碳拉曼峰相对强度,以三倍于噪声强度的信号作为检出限标准,估算出该系统对于二氧化碳的检测限约为0.13 mg·L^-1(66 ppm)。Raman spectroscopy is used in many fields with advantages of no sample pretreatment and simultaneous multiple species detection,while the disadvantage of low sensitivity limits its further a pplication.In order to improve the sensitivity of Raman gas detection,a method for enhancing the gas Raman signal based on a folded near-concentric cavity is reported in this paper.By inserting a high reflectivity plane mirror into the center of multiple reflectors,the cavity body is folded from the center,so that the beams in the center of the cavity overlap with each other to increase the light density and luminous flux,thereby improving the detection sensitivity of the system.Ray tracing and flux analysis are performed on the different cavity modes using TracePro software(laser:300 mW@532 nm,reflectance:99%@532 nm).The results show that the optical cavity folding method can significantly increase the optical flux at the center of the reflecting cavity.When the number of reflections in the folded near concentric cavity is 68 times,the luminous flux at the center of the waist is 22.35 W,which is about 1.5 times enhancement compared with the unfolded near-concentric reflecting cavity.In order to verify the simulation results,a gas detection Raman spectroscopy system with folded near-concentric cavity is set up.The experimental results show that the folded near-concentric cavity has the best enhancement,reaching 49 times;next is near concentric cavity about 36 times;the third is folding the concentric cavity,a pproximately 24 times;the last is the concentric cavity,just 17 times.The signal-to-noise ratio of the gas Raman signal collected by the folded near-concentric cavity is 1.4 times higher than that of the unfolded near-concentric cavity.According to the relative intensity of the carbon dioxide Raman peak in the air,we can calculate the limit of detection for CO 2 using 3-σcriterion standard with the value of 0.13 mg·L-1(66 ppm).

关 键 词：拉曼光谱技术 气体探测 探测灵敏度 折叠近共心腔 

分 类 号：O433.1[机械工程—光学工程]