Antiresonant fiber-enhanced Raman spectroscopy gas sensing with 1 ppm sensitivity

Area of Science:

• Optics and Photonics
• Spectroscopy
• Environmental Sensing

Background:

• Antiresonant hollow-core fiber (AR-HCF) offers low attenuation and broad bandwidth.
• AR-HCF has lower numerical aperture, reducing Raman signal collection efficiency compared to other fibers.
• AR-HCF effectively suppresses higher-order modes, enabling enhanced gas sensing capabilities.

Purpose of the Study:

• To enhance Raman gas sensing using AR-HCF for low-concentration detection.
• To investigate silica background signal attenuation in AR-HCF for improved spectroscopy.
• To develop a spatial filtering method for reducing baseline noise in Raman gas sensing.

Main Methods:

• Combined nodeless AR-HCF with Raman spectroscopy in a forward scattering configuration.
• Investigated silica background attenuation behavior within the AR-HCF.
• Employed a multimode fiber as a spatial filter to reduce silica signal and baseline.

Main Results:

• Observed natural isotopes of CO2 (¹²C¹⁶O₂, ¹³C¹⁶O₂, ¹²C¹⁸O¹⁶O) in ambient air using a 5-meter AR-HCF.
• Achieved limits of detection of 0.5 ppm for ¹³C¹⁶O₂ and 1.2 ppm for ¹²C¹⁶O₂.
• Demonstrated effective silica signal filtering and baseline reduction using a multimode fiber spatial filter.

Conclusions:

• Fiber-Enhanced Raman Spectroscopy (FERS) with AR-HCF shows significant potential for isotopic and multi-gas sensing.
• Increasing AR-HCF length effectively enhances low-concentration gas detection capabilities.
• The developed methods enable sensitive and selective detection of trace gases.