Fiber-Enhanced Raman Spectroscopy for Trace-Gas Sensing in the High-Concentration Gas Background With an Anti-Resonant Hollow Core Fiber

Abstract

In this article, with an anti-resonant hollow core fiber (ARHCF), fiber-enhanced Raman spectroscopy (FERS) for trace-gas sensing in a high-concentration gas background is demonstrated for the first time. The performance of the apparatus is verified by detecting trace-gas in the high concentration SF6 and gaseous impurities in the high concentration C2H6. With a 1.5 W laser source and 60 s exposure time, the limit of detection (LOD) of gases at tens of ppm levels is achieved, including carbonyl sulfide (COS), carbon tetrafluoride (CF4), carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), acetylene (C2H2), ethylene (C2H4), propyne (C3H4), propylene (C3H6), and propane (C3H8). Quantification of multi-gas with great accuracy exceeding 94% is also realized. It shows that the FERS can demonstrate the ability of multi-gas sensing with high selectivity, sensitivity, and accuracy.

Trace Analysis of C4F7N Insulating Gas Mixtures by Spontaneous Raman Spectroscopy and Gas Chromatography

“…SRS trace gas analysis has long been hindered by the relatively small scattering cross sections of order 10 –31 cm 2 /steradian for gases . However, numerous recent efforts into the development of enhancement techniques by way of optical capillaries, − fibers, − microcavities, and conventional resonator cavities − that increase the interaction strength and/or the SRS light collection efficiency have dramatically improved the prospects of SRS for trace gas sensing. Among these enhancement strategies, the utilization of a nonresonant multipass cavity offers particular robustness. − This technique has demonstrated trace sensitivity well into the parts-per-billion range, , while requiring minimal power consumption and no active optical resonance stabilization.…”

High-Precision Trace Hydrogen Sensing by Multipass Raman Scattering

“…In hollow-core fibers as long as 2 m, hydrogen was probed with an estimated LOD of 4.7 ppm using either rotational or vibrational transitions [30,31]. Much progress in improving FERS has also been made recently by mitigating the issue of gas throughput by utilization of larger, anti-resonant, waveguides [32]. Another means of achieving Raman enhancement is using optical resonators.…”

Narrow-Linewidth Pr:YLF Laser for High-Resolution Raman Trace Gas Spectroscopy

“…To circumvent this limitation, numerous approaches to SRS enhancement have been researched and are continually being improved. Approaches based on cavities [9][10][11][12][13][14][15][16][17][18][19] or on waveguides [20][21][22][23][24][25] have demonstrated the ability to routinely detect at parts-per-million (ppm) concentrations. For example, in cavity-enhanced Raman scattering (CERS), high-power green laser light obtained via frequency doubling can be introduced into an external high-finesse optical cavity to create circulating power of 1 kW [26].…”