Methane sensing in the mid-IR using short wave IR photon counting detectors via non-linear interferometry

TL;DR

This paper introduces a novel mid-infrared methane sensor that uses non-linear interferometry to shift measurement wavelengths to the short-wave infrared, enabling sensitive detection with improved performance over existing methods.

Contribution

The paper presents a new non-linear interferometry technique for methane sensing that operates at wavelengths with better detector sensitivity, allowing for compact, field-deployable sensors with high precision.

Findings

Successfully measured small methane concentrations with high precision.

The method can outperform existing sensors at high non-linear gain.

Potential for detection at ranges up to 100 meters.

Abstract

We demonstrate a novel MIR methane sensor shifting measurement wavelength to SWIR (1.55$\mu$m) by using non-linear interferometry. The technique exploits the interference effects seen in three-wave mixing when pump, signal, and idler modes make a double pass through a nonlinear crystal. The method allows sensing at wavelengths where detectors are poor ($>$3$\mu$m) and detection at wavelengths where photon counting sensitivity can be achieved. In a first experimental demonstration, we measured a small methane concentration inside a gas cell with high precision. This interferometer can be built in a compact design for field operations and potentially enable the detection of low concentrations of methane at up to 100m range. Signal-to-noise ratio calculations show that the method can outperform existing short wavelength ($\sim$1.65$\mu$m) integrated path differential absorption direct sensing at high ($>$$10^{-4}$) non-linear gain.