Compact, Micro-Optic Hollow Core Fibre Device for Fibre-Enhanced Gas-Phase Raman Spectroscopy

Fibre-enhanced Raman spectroscopy is an attractive technique for analysis of multispecies gas mixtures, providing both high sensitivity and specificity (see e.g. [1]). In this approach, hollow core optical fibre (HCF) is successfully used to enhance the gas-light interaction length to achieve high sensitivity and results so far are promising for a diverse range of applications, including industrial process monitoring. Yet, up until now, all reported works rely on free-space components. Aligning instruments based on free-space opto-mechanical components can be cumbersome, susceptible to drift caused by environmental factors such as temperature variations and vibration and also leads to increased instrument footprint. Integrated HCF devices are now emerging [2] so here, we propose a novel compact, integrated HCF coupling micro-optics approach for gas-phase Raman spectroscopy. The pump laser delivery into the HCF, gas ingress, and Raman collection optics are combined into a single monolithic structure, which is packaged into an aluminium casing with dimensions of 70 × 12 × 9 mm.