Impact of Pressure-Induced Differential Refractive Index in Raman Spectroscopy using Hollow-Core Fibres

Raman spectroscopy is an attractive technique for simultaneous analysis of multiple gas species. Exploiting hollow-core microstructured optical fibres (HC-MOFs) for enhanced gas-light interaction length allows for extremely low detection limits of, e.g., 0.2 ppm methane [1] . Recently, we reported that extremely small changes in the refractive indices of the gases inside the core and cladding regions (as induced by differential gas pressure) significantly impact the optical properties of these fibres [2] . Here we exploit this effect to almost double the Raman signal.