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Raman spectroscopy is a powerful diagnostic method for gas analysis due to its advantages like non-invasiveness and fast speed. However, its applications are greatly restricted because of the weak signal level caused by small scattering cross section. In order to enhance the Raman signal level and improve the detection sensitivity, a sample cell of confocal cavity is designed and the enhanced Raman signal of ambient air based on this cavity is demonstrated experimentally. The confocal cavity is constructed with a pair of plano-concave reflectors with a curvature radius of 150 mm and reflectivity of 92%. This low reflectivity design not only allows for bandwidth matching with the line-width of excitation laser but also makes the resonant condition satisfied easily. The measured output power of the confocal cavity is over 42 mW in resonant condition, which gives a coupling efficiency of 87.5% when divided with the input power 48 mW. The high coupling efficiency enables the output power efficiently to reach 11 times that for the intra-cavity laser power in one direction. Raman scattering of ambient air is tested to verify the performance of the confocal cavity. In our experiments, the Raman signals are collected in a forward scattering configuration by an imaging Raman spectrometer which is connected to a CCD camera. Strong Raman signals of O2 and N2, even H2O are observed with 1 s exposure time in resonant condition, and rotational lines (O-branch and S-branch) of O2 and N2 are also clearly detected when exposure time is set to be 10 s. Compared with the results obtained without confocal cavity, the Raman signal level is enhanced 17 times and the signal-to-noise ratio is improved twice. In addition, a limit of detection (3) at a magnitude of 200 ppm for CO2 in ambient air is achieved for the resonant confocal cavity. These results indicate that the system can significantly enhance the spontaneous Raman scattering signal level and improve the detection sensitivity. Furthermore, the confocal cavity is applicable to the Raman analyses of other gas samples.
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Keywords:
- resonant confocal cavity /
- Raman scattering /
- gas analysis
[1] Zhang L, Zheng H Y, Wang Y P, Ding L, Fang L 2016 Acta Phys. Sin. 65 054206 (in Chinese)[张莉, 郑海洋, 王颖萍, 丁蕾, 方黎 2016 物理学报 65 054206]
[2] Buldakov M A, Korolkov V A, Matrosov I I, Petrov D V, Tikhomirov A A 2013 J. Opt. Technol. 80 426
[3] Jochum T, Fischer J C, Trumbore S, Popp J, Frosch T 2015 Anal. Chem. 87 11137
[4] Schlter S, Krischke F, Popovska-Leipertz N, Seeger T, Breuer G, Jeleazcov C, Schttler J, Leipertz A 2015 J. Raman Spectrosc. 46 708
[5] Shreve A P, Cherepy N J, Mathies R A 1992 Appl. Spectrosc. 46 707
[6] Troyanova-Wood M A, Petrov G I, Yakovlev V V 2013 J. Raman Spectrosc. 44 1789
[7] Son H 2013 Sensors and Actuators B:Chemical 176 64
[8] Yang X, Chang A S P, Chen B, Gu C, Bondet T C 2013 Sensors and Actuators B: Chemical 176 64
[9] Guo J J, Yang D W, Liu C H 2016 Spectrosc. Spect. Anal. 36 96 (in Chinese) [郭金家, 杨德旺, 刘春昊 2016 光谱学与光谱分析 36 96]
[10] Yu A L, Zuo D L, Li B, Gao J, Wang X B 2016 Appl. Opt. 55 3650
[11] Rupp S, Off A, Seitz-Moskaliuk H, James M T, Telle H H 2015 Sensors 15 23110
[12] Utsav K, Silver J A, Hovde D C, Varghese P L 2011 Appl. Opt. 50 4805
[13] Hill R A, Hartley D L 1974 Appl. Opt. 13 186
[14] Li X Y, Xia Y X, Zhan L, Huang J M 2008 Opt. Lett. 33 2143
[15] Yang D W, Guo J J, Du Z F, Wang Z N, Zheng R E 2015 Spectrosc. Spect. Anal. 35 645 (in Chinese) [杨德旺, 郭金家, 杜增丰, 王振南, 郑荣儿 2015 光谱学与光谱分析 35 645]
[16] Li X Y, Xia Y X, Huang J M, Zhan L 2008 Chin. Phys. Lett. 25 3326
[17] King D A, Pittaro R J 1998 Opt. Lett. 23 774
[18] Thorstensen J, Haugholt K H, Ferber A, Bakke K A H, Tschudi J 2014 J. Europ. Opt. Soc. Rap. Public. 9 14054
[19] Salter R, Chu J, Hippler M 2012 Analyst 137 4669
[20] Karpf A, Rao G N 2015 Appl. Opt. 54 6085
[21] Zuo D L, Yu A L, Li Z, Wang X B, Xiong Y H 2015 Proc. of SPIE 9611 Imaging Spectrometry XX San Diego, California, United States, August 9, 2015 96110N-19
[22] Saleh B E A, Teich M C 2007 Fundamentals of Photonics (Second Edition) (Hoboken: Wiley-Interscience)pp394395
[23] Barnes J A, Gough T E, Stoer M 1999 Rev. Sci. Instrum. 70 3515
[24] Hanf S, Keiner R, Yan D, Popp J, Frosch T 2014 Anal. Chem. 86 5278
[25] Zhang S G, Hu S X, Lin J M, Shao S S, Cao K F, Huang J, Xu Z H 2014 Infrared Laser Eng. 43 1135 (in Chinese) [张世国, 胡顺星, 林金明, 邵石生, 曹开法, 黄见, 徐之海 2014 红外与激光工程 43 1135]
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[1] Zhang L, Zheng H Y, Wang Y P, Ding L, Fang L 2016 Acta Phys. Sin. 65 054206 (in Chinese)[张莉, 郑海洋, 王颖萍, 丁蕾, 方黎 2016 物理学报 65 054206]
[2] Buldakov M A, Korolkov V A, Matrosov I I, Petrov D V, Tikhomirov A A 2013 J. Opt. Technol. 80 426
[3] Jochum T, Fischer J C, Trumbore S, Popp J, Frosch T 2015 Anal. Chem. 87 11137
[4] Schlter S, Krischke F, Popovska-Leipertz N, Seeger T, Breuer G, Jeleazcov C, Schttler J, Leipertz A 2015 J. Raman Spectrosc. 46 708
[5] Shreve A P, Cherepy N J, Mathies R A 1992 Appl. Spectrosc. 46 707
[6] Troyanova-Wood M A, Petrov G I, Yakovlev V V 2013 J. Raman Spectrosc. 44 1789
[7] Son H 2013 Sensors and Actuators B:Chemical 176 64
[8] Yang X, Chang A S P, Chen B, Gu C, Bondet T C 2013 Sensors and Actuators B: Chemical 176 64
[9] Guo J J, Yang D W, Liu C H 2016 Spectrosc. Spect. Anal. 36 96 (in Chinese) [郭金家, 杨德旺, 刘春昊 2016 光谱学与光谱分析 36 96]
[10] Yu A L, Zuo D L, Li B, Gao J, Wang X B 2016 Appl. Opt. 55 3650
[11] Rupp S, Off A, Seitz-Moskaliuk H, James M T, Telle H H 2015 Sensors 15 23110
[12] Utsav K, Silver J A, Hovde D C, Varghese P L 2011 Appl. Opt. 50 4805
[13] Hill R A, Hartley D L 1974 Appl. Opt. 13 186
[14] Li X Y, Xia Y X, Zhan L, Huang J M 2008 Opt. Lett. 33 2143
[15] Yang D W, Guo J J, Du Z F, Wang Z N, Zheng R E 2015 Spectrosc. Spect. Anal. 35 645 (in Chinese) [杨德旺, 郭金家, 杜增丰, 王振南, 郑荣儿 2015 光谱学与光谱分析 35 645]
[16] Li X Y, Xia Y X, Huang J M, Zhan L 2008 Chin. Phys. Lett. 25 3326
[17] King D A, Pittaro R J 1998 Opt. Lett. 23 774
[18] Thorstensen J, Haugholt K H, Ferber A, Bakke K A H, Tschudi J 2014 J. Europ. Opt. Soc. Rap. Public. 9 14054
[19] Salter R, Chu J, Hippler M 2012 Analyst 137 4669
[20] Karpf A, Rao G N 2015 Appl. Opt. 54 6085
[21] Zuo D L, Yu A L, Li Z, Wang X B, Xiong Y H 2015 Proc. of SPIE 9611 Imaging Spectrometry XX San Diego, California, United States, August 9, 2015 96110N-19
[22] Saleh B E A, Teich M C 2007 Fundamentals of Photonics (Second Edition) (Hoboken: Wiley-Interscience)pp394395
[23] Barnes J A, Gough T E, Stoer M 1999 Rev. Sci. Instrum. 70 3515
[24] Hanf S, Keiner R, Yan D, Popp J, Frosch T 2014 Anal. Chem. 86 5278
[25] Zhang S G, Hu S X, Lin J M, Shao S S, Cao K F, Huang J, Xu Z H 2014 Infrared Laser Eng. 43 1135 (in Chinese) [张世国, 胡顺星, 林金明, 邵石生, 曹开法, 黄见, 徐之海 2014 红外与激光工程 43 1135]
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