Improved Visible-Guiding Anti-Resonant Hollow-Core Fiber for Gas-Phase Raman Spectroscopy

Abstract

Gas-filled hollow-core optical fibers (HCFs) provide an enhanced gas-light interaction length which can be exploited for high-sensitivity laser-based trace gas detection [1]. Here, we focus on HCF-based spontaneous gas-phase Raman spectroscopy; this is an attractive approach for optical gas sensing as multispecies gas mixtures can be detected with a single laser source. While the merits of using HCF-based gas Raman detection have been previously described [1], and limits of detection (LoD) as low as 0.15 ppm reported [2], so far there has been limited discussion on HCF design optimization to maximize the system performance. Here, the design, fabrication and testing of a visible-guiding 10-element single-cladding ring (“tubular”) anti-resonant HCF (10T-ARF) is reported. We show that this design provides improved Raman signal (via lower attenuation of both the fundamental mode (FM) and higher order modes (HOMs) and larger numerical aperture) in combination with faster gas filling time (due to a larger core diameter) without compromising on bend performance and therefore device footprint.