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.

scholarly journals Application of Near-Infrared Optical Feedback Cavity Enhanced Absorption Spectroscopy (OF-CEAS) to the Detection of Ammonia in Exhaled Human Breath

Sensors ◽  
2019 ◽  
Vol 19 (17) ◽  
pp. 3686
Author(s):  
Zhifu Luo ◽  
Zhongqi Tan ◽  
Xingwu Long
Keyword(s):  
Detection Limit ◽  
Absorption Spectroscopy ◽  
Spectral Resolution ◽  
Optical Feedback ◽  
Low Pressure ◽  
High Spectral Resolution ◽  
Trace Gas ◽  
Human Breath ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy

The qualitative and quantitative analysis to trace gas in exhaled human breath has become a promising technique in biomedical applications such as disease diagnosis and health status monitoring. This paper describes an application of a high spectral resolution optical feedback cavity enhanced absorption spectroscopy (OF-CEAS) for ammonia detection in exhaled human breath, and the main interference of gases such as CO2 and H2O are approximately eliminated at the same time. With appropriate optical feedback, a fibered distributed feedback (DFB) diode laser emitting at 1531.6 nm is locked to the resonance of a V-shaped cavity with a free spectral range (FSR) of 300 MHz and a finesse of 14,610. A minimum detectable absorption coefficient of αmin = 2.3 × 10−9 cm−1 is achieved in a single scan within 5 s, yielding a detection limit of 17 ppb for NH3 in breath gas at low pressure, and this stable system allows the detection limit down to 4.5 ppb when the spectra to be averaged over 16 laser scans. Different from typical CEAS with a static cavity, which is limited by the FSR in frequency space, the attainable spectral resolution of our experimental setup can be up to 0.002 cm−1 owing to the simultaneous laser frequency tuning and cavity dither. Hence, the absorption line profile is more accurate, which is most suitable for low-pressure trace gas detection. This work has great potential for accurate selectivity and high sensitivity applications in human breath analysis and atmosphere sciences.

scholarly journals RF noise induced laser perturbation for improving the performance of non-resonant cavity enhanced absorption spectroscopy

2014 ◽  
Vol 22 (14) ◽  
pp. 17030 ◽  
Author(s):  
Luca Ciaffoni ◽  
John Couper ◽  
Gus Hancock ◽  
Robert Peverall ◽  
Peter A. Robbins ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Resonant Cavity ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
Rf Noise

scholarly journals Comparison of optical-feedback cavity-enhanced absorption spectroscopy and gas chromatography for ground-based and airborne measurements of atmospheric CO concentration

2017 ◽  
Vol 10 (5) ◽  
pp. 1803-1812 ◽  
Author(s):  
Irène Ventrillard ◽  
Irène Xueref-Remy ◽  
Martina Schmidt ◽  
Camille Yver Kwok ◽  
Xavier Faïn ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
High Performance ◽  
Optical Feedback ◽  
Mercuric Oxide ◽  
Gas Chromatograph ◽  
Laser Spectrometer ◽  
Airborne Measurements ◽  
Enhanced Absorption ◽  
Cavity Enhanced Absorption Spectroscopy ◽  
Compact Size

Abstract. We present the first comparison of carbon monoxide (CO) measurements performed with a portable laser spectrometer that exploits the optical-feedback cavity-enhanced absorption spectroscopy (OF-CEAS) technique, against a high-performance automated gas chromatograph (GC) with a mercuric oxide reduction gas detector (RGD). First, measurements of atmospheric CO mole fraction were continuously collected in a Paris (France) suburb over 1 week. Both instruments showed an excellent agreement within typically 2 ppb (part per billion in volume), fulfilling the World Meteorological Organization (WMO) recommendation for CO inter-laboratory comparison. The compact size and robustness of the OF-CEAS instrument allowed its operation aboard a small aircraft employed for routine tropospheric air analysis over the French Orléans forest area. Direct OF-CEAS real-time CO measurements in tropospheric air were then compared with later analysis of flask samples by the gas chromatograph. Again, a very good agreement was observed. This work establishes that the OF-CEAS laser spectrometer can run unattended at a very high level of sensitivity ( <  1 ppb) and stability without any periodic calibration.

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