Sensing of gas mixtures via nonlinear interferometry

Abstract We demonstrate the use of a nonlinear interferometer with bulk lithium niobate crystal for sensing of gas mixtures over broadband mid-infrared (mid-IR) range of wavelengths. Our method utilizes spontaneous parametric down-conversion to generate correlated photon pairs in the visible and mid-IR ranges. We show that by leveraging the phase-matching properties of lithium niobate crystal, it is possible to access the ‘fingerprint’ region of greenhouse gases in the mid-IR range by detection of correlated visible light signal. Our technique enables simultaneous detection of gas mixtures with high spectral resolution and fast readout without the need for specialized mid-IR equipment. The experimental results show its applicability to molecular gas sensing, paving the way for new advancements in environmental monitoring.