High sensitivity liquid phase measurements using broadband cavity enhanced absorption spectroscopy (BBCEAS) featuring a low cost webcam based prism spectrometer

The Analyst ◽  
2013 ◽  
Vol 138 (21) ◽  
pp. 6372 ◽  
Author(s):  
Zhechao Qu ◽  
Julia Engstrom ◽  
Donald Wong ◽  
Meez Islam ◽  
Clemens F. Kaminski
Keyword(s):  
Liquid Phase ◽  
Absorption Spectroscopy ◽  
Low Cost ◽  
High Sensitivity ◽  
Phase Measurements ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy

scholarly journals Study of a periodic spectral fluctuation existing in a fibered optical feedback cavity-enhanced absorption spectroscopy (OF-CEAS)

2019 ◽  
Vol 15 (1) ◽  
Author(s):  
Zhifu Luo ◽  
Zhongqi Tan ◽  
Xingwu Long
Keyword(s):  
Absorption Spectroscopy ◽  
Optical Feedback ◽  
Resonant Cavity ◽  
High Sensitivity ◽  
Trace Gas ◽  
Ripple Effect ◽  
Interference Theory ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
Theoretical Analyses

Abstract A special periodic spectral fluctuation is observed during the study of a fibered high sensitivity optical feedback cavity-enhanced absorption spectroscopy (OF-CEAS) for the measurement of trace gas. This spectral fluctuation is different from some phenomenon observed in former OF-CEAS which contain a resonant cavity with V-shaped configuration, such as the etalon effect and the spectral ripple effect. To reveal why this phenomenon happens and how it works, a series of hypothesis are proposed and tested, and the results show that the multi-beam interference of resonance light at the input mirror of the resonant cavity is the main reason for this phenomenon. Based on the multi-beam interference theory, a mathematical modeling of this phenomenon is built, and the theoretical analyses agree well with the experimental results. Some methods to eliminate this phenomenon are proposed and implemented, and the 1σ noise equivalent absorption coefficient of 7.6 × 10− 10 cm− 1 Hz-1/2 is attained with this robust and compact OF-CEAS system.

Prism-based Broadband Optical Cavity (400 – 1600 nm) for High-Sensitivity Trace Gas Sensing by Cavity Enhanced Absorption Spectroscopy

2020 ◽  
Author(s):  
Weidong Chen ◽  
Gaoxuan Wang ◽  
Lingshuo Meng ◽  
Qian Gou ◽  
Azer Yalin ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Gas Sensing ◽  
Optical Cavity ◽  
Wavelength Region ◽  
High Sensitivity ◽  
Central Wavelength ◽  
Enhanced Absorption ◽  
High Reflectivity ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
High Finesse

<p>The use of high reflectivity dielectric mirrors to form a high finesse optical cavity allows one to achieve long optical path lengths of up to several kilometres for high-sensitivity spectroscopy applications [1]. However, the high reflectivity of a dielectric mirror is achieved via constructive interference of the Fresnel reflection at the interfaces produced by multilayer coatings of alternate high and low refractive index materials. This wavelength-dependent coating limits the bandwidth of the mirror's high reflectivity to only a few percent of the designed central wavelength [2].</p><p>In this paper, we report on the development of a novel optical cavity based on prism used as cavity reflector through total internal reflection combined with Brewster angle incidence [3], which offers a high-finesse optical cavity operating in a broadband wavelength region from 400 to longer than 1600 nm. Cavity Enhanced Absorption Spectroscopy (CEAS) of NO<sub>2</sub>, NO<sub>3</sub>, and H<sub>2</sub>O vapor was applied to determine the achieved prism reflectivity over a broad spectral range from 400 nm to 1600 nm.</p><p>Experimental details and preliminary results will be presented. The developed prism-based cavity is specifically adapted for the needs of broadband measurement of multi-molecular absorber or/and wavelength-dependent extinction coefficient of aerosols over a broad spectral region.</p><p>Acknowledgments. This work is supported by the French national research agency (ANR) under the CaPPA (ANR-10-LABX-005), the MABCaM (ANR-16-CE04-0009) and the MULTIPAS (ANR-16-CE04-0012) contracts. The authors thank the financial support from the CPER CLIMIBIO program.</p><p>REFERENCES</p><p>[1] S. S. Brown, "Absorption spectroscopy in high-finesse cavities for atmospheric studies", Chem. Rev. <strong>103</strong> (2003) 5219-5238.</p><p>[2] G.R. Fowles, Introduction to Modern Optics, 2nd ed. (Rinehart and Winston, 1975), p. 328.</p><p>[3] B. Lee, K. Lehmann, J. Taylor and A. Yalin, "A high-finesse broadband optical cavity using calcium fluoride prism retroreflectors", Opt. Express <strong>2</strong><strong>2</strong> (2014) 11583-11591.</p>

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