-
摘要:
为解决传统拉曼光谱信号强度弱、信噪比低的问题,本文提出一种新型的共聚焦拉曼系统,通过外接光子晶体光纤实现共聚焦点的绝对共轭,总结了光子晶体光纤耦合过程中出现的技术问题,并对实际样品进行测试。与Thorlabs、OZ两种常规共聚焦拉曼系统所用光纤、Witec 532 nm-alpha300R拉曼系统进行比较,在相同激光强度和积分时间下,本文信噪比为73.8382,显著高于Thorlabs、OZ两种光纤的37.1557和40.0342,而相较于Witec 532 nm-alpha300R的65.5312,也提升了12.68%,高质量的拉曼信号使得该绝对共轭共聚焦拉曼系统具有广阔的市场前景和超高的市场竞争力。
Abstract:To solve the problems of weak signal strength and low signal-to-noise ratio in traditional Raman spectroscopy, a new confocal Raman system is proposed in this paper. The absolute conjugation of the confocal point is realized by external photonic crystal fiber. The technical problems in the coupling process of photonic crystal fiber are summarized, and the actual samples are tested. Compared with conventional confocal Raman fibers such as Thorlabs and OZ and Witec 532 nm-alpha300R Raman system, the signal-to-noise ratio in this paper is 73.8382 at the same laser intensity and integration time, which is significantly higher than that of Thorlabs and OZ (37.1557 and 40.0342, respectively). Compared with the signal-to-noise ratio of 65.5312 for Witec 532 nm-alpha300R, it also increased by 12.68%. High-quality Raman signal makes the absolute conjugated confocal Raman system have broad market prospects and ultra-high market competitiveness.
-
Key words:
- Raman spectrometer /
- absolute conjugation /
- photonic crystal fiber /
- SNR
-
Overview: After the discovery of the Raman scattering effect, due to its high sensitivity and non-invasiveness to test samples, it has been more and more used in materials testing, jewelry identification and other fields. However, in the direction of biological samples, such as bacterial metabolism detection, microbial discrimination, etc., the intensity of Raman spectroscopy is relatively weak, and the signal-to-noise ratio is low. As a conventional Raman signal acquisition method, the confocal Raman system occupies an important position in many Raman systems. However, most confocal Raman systems mostly use small holes or slits, and rarely use photonic crystal fibers. Aiming at the problems of weak signal strength and low signal-to-noise ratio of traditional Raman spectroscopy, a new confocal Raman system is proposed. The system realizes the absolute conjugation of the confocal point through the external photonic crystal fiber. Secondly, the difference in imaging accuracy between photonic crystal fiber and other single-mode fibers is verified, and it is found that the imaging accuracy of photonic crystal fiber is much higher than that of ordinary single-mode fiber. Then, the actual samples were tested and verified, and Escherichia coli with high background noise was screened out. The test results were compared with the optical fibers used in Thorlabs and OZ conventional confocal Raman systems and Witec 532 nm-alpha300R confocal Raman systems. Under the conditions of the same laser intensity of 3 mW and integration time of 5 s, the signal-to-noise ratio obtained is 73.8382, which is higher than that of Thorlabs and OZ systems. Compared with the 65.5312 of the Witec 532 nm-alpha300R confocal Raman system, the Raman signal quality of the two single-mode fibers are 37.1557 and 40.0342 respectively, an increase of 12.68%. It can be seen that the quality of the Raman signal obtained in this paper is relatively high. Absolutely conjugated confocal Raman system will promote the application of photonic crystal fiber in biological cell Raman, and has a very broad application prospect.
-
表 1 两种光纤和Witec与本文信噪比对比表
Table 1. SNR comparison table between Witec and this paper
Thorlabs OZ Witec Our SNR 37.2384 40.0318 64.6236 70.5219 36.8945 40.2175 66.1375 71.3961 37.3341 39.8532 65.8325 73.5965 Average 37.1557 40.0342 65.5312 73.8382 -
[1] Beyssac O, Goffé B, Chopin C, et al. Raman spectra of carbonaceous material in metasediments: a new geothermometer[J]. J Metamorp Geol, 2002, 20(9): 859-871. doi: 10.1046/j.1525-1314.2002.00408.x
[2] Bersani D, Lottici P P. Applications of Raman spectroscopy to gemology[J]. Anal Bioanal Chem, 2010, 397(7): 2631-2646. doi: 10.1007/s00216-010-3700-1
[3] Dieing T, Hollricher O, Toporski J. Confocal Raman Microscopy[M]. Berlin, Heidelberg: Springer, 2011.
[4] Stiles P L, Dieringer J A, Shah N C, et al. Surface-enhanced Raman spectroscopy[J]. Annu Rev Anal Chem, 2008, 1: 601-626. doi: 10.1146/annurev.anchem.1.031207.112814
[5] Carey P. Biochemical Applications of Raman and Resonance Raman Spectroscopes[M]. Amsterdam: Elsevier, 2012.
[6] Stöckle R M, Suh Y D, Deckert V, et al. Nanoscale chemical analysis by tip-enhanced Raman spectroscopy[J]. Chem Phys Lett, 2000, 318(1-3): 131-136. doi: 10.1016/S0009-2614(99)01451-7
[7] Russell P S J. Photonic band gaps[J]. Phys World, 1992, 5(8): 37-42. doi: 10.1088/2058-7058/5/8/31
[8] Knight J C, Birks T A, Russell P S J, et al. All-silica single-mode optical fiber with photonic crystal cladding[J]. Opt Lett, 1996, 21(19): 1547-1549. doi: 10.1364/OL.21.001547
[9] Cregan R F, Mangan B J, Knight J C, et al. Single-mode photonic band gap guidance of light in air[J]. Science, 1999, 285(5433): 1537-1539. doi: 10.1126/science.285.5433.1537
[10] 陈月娥, 侯蓝田. Yb3+掺杂双包层光子晶体光纤制备研究[J]. 光电工程, 2009, 36(2): 62-66. doi: 10.3969/j.issn.1003-501X.2009.02.012 https://www.cnki.com.cn/Article/CJFDTOTAL-GDGC200902014.htm
Chen Y E, Hou L T. Preparation of Yb3+ doped double-clad photonic crystal fiber[J]. Opto-Electron Eng, 2009, 36(2): 62-66. doi: 10.3969/j.issn.1003-501X.2009.02.012 https://www.cnki.com.cn/Article/CJFDTOTAL-GDGC200902014.htm
[11] 张学典, 袁曼曼, 常敏, 等. 正方形空气孔光子晶体光纤特性分析[J]. 光电工程, 2018, 45(5): 20-28. doi: 10.12086/oee.2018.170633
Zhang X D, Yuan M M, Chang M, et al. Characteristics in square air hole structure photonic crystal fiber[J]. Opto-Electron Eng, 2018, 45(5): 20-28. doi: 10.12086/oee.2018.170633
[12] 王清月, 胡明列, 柴路. 光子晶体光纤非线性光学研究新进展[J]. 中国激光, 2006, 33(1): 57-66. doi: 10.3321/j.issn:0258-7025.2006.01.014
Wang Q Y, Hu M L, Chai L. Progress in nonlinear optics with photonic crystal fibers[J]. Chin J Lasers, 2006, 33(1): 57-66. doi: 10.3321/j.issn:0258-7025.2006.01.014
[13] Folkenberg J R, Nielsen M D, Mortensen N A, et al. Polarization maintaining large mode area photonic crystal fiber[J]. Opt Express, 2004, 12(5): 956-960. doi: 10.1364/OPEX.12.000956
[14] Polis B, Imiela A, Polis L, et al. Raman spectroscopy for medulloblastoma[J]. Child's Nervous System, 2018, 34(12): 2425-2430. doi: 10.1007/s00381-018-3906-7
[15] 吕明磊. 拉曼光谱基线校正与噪声抑制技术研究[D]. 成都: 电子科技大学, 2017.
Lv M L. Baseline correction and noise suppression of Raman spectroscopy[D]. Chengdu: University of Electronic Science and Technology of China, 2017.
[16] 何英杰, 谢东海, 钟若飞. 基于高光谱影像的SG滤波算法的研究[J]. 首都师范大学学报(自然科学版), 2018, 39(2): 70-75. doi: 10.3969/j.issn.1004-9398.2018.02.014
He Y J, Xie D H, Zhong R F. Research on SG filtering algorithm based on hyperspectral image[J]. J Cap Norm Univ (Nat Sci Ed), 2018, 39(2): 70-75. doi: 10.3969/j.issn.1004-9398.2018.02.014
[17] 尚韬, 李锋, 刘增基. 基于光子晶体光纤的拉曼放大器特性研究[J]. 通信学报, 2008, 29(8): 63-68. doi: 10.3321/j.issn:1000-436X.2008.08.008
Shang T, Li F, Liu Z J. Numerical analysis of Raman amplifier based on triangular photonic crystal fiber[J]. J Commun, 2008, 29(8): 63-68. doi: 10.3321/j.issn:1000-436X.2008.08.008
[18] 陈金敏. 微弱拉曼光谱成像信息提取及SNR估计[J]. 数字技术与应用, 2019, 37(4): 100-103. https://www.cnki.com.cn/Article/CJFDTOTAL-SZJT201904056.htm
Chen J M. Extraction of weak raman spectral imaging information and SNR estimation[J]. Digit Technol Appl, 2019, 37(4): 100-103. https://www.cnki.com.cn/Article/CJFDTOTAL-SZJT201904056.htm
[19] Zhang Z M, Chen S, Liang Y Z, et al. An intelligent background-correction algorithm for highly fluorescent samples in Raman spectroscopy[J]. J Raman Spectrosc, 2010, 41(6): 659-669. doi: 10.1002/jrs.2500