A fiber Fabry-Perot cavity based spectroscopic gas sensor

TL;DR

This paper introduces a miniaturized, fiber-based Fabry-Perot cavity spectroscopic sensor capable of broadband gas analysis and concentration measurement, combining high sensitivity with compactness and robustness.

Contribution

The work presents a novel fiber Fabry-Perot cavity sensor with wide tunability and stable operation, enabling broadband spectroscopy and concentration detection in a miniaturized platform.

Findings

Demonstrated broadband spectral sampling over tens of terahertz.

Implemented a low-noise, fast scan method using Pound-Drever-Hall locking.

Achieved sensitive detection of oxygen A-band absorption features.

Abstract

Optical spectroscopic sensors are powerful tools for analysing gas mixtures in industrial and scientific applications. Whilst highly sensitive spectrometers tend to have a large footprint, miniaturized optical devices usually lack sensitivity or wideband spectroscopic coverage. By employing a widely tunable, passively stable fiber Fabry-Perot cavity (FFPC), we demonstrate an absorption spectroscopic device that continuously samples over several tens of terahertz. Both broadband scans using cavity mode width spectroscopy to identify the spectral fingerprints of analytes and a fast, low-noise scan method for single absorption features to determine concentrations are exemplary demonstrated for the oxygen A-band. The novel scan method uses an injected modulation signal in a Pound-Drever-Hall feedback loop together with a lock-in measurement to reject noise at other frequencies. The FFPC-based approach provides a directly fiber coupled, extremely miniaturized, light-weight and robust platform for analyzing small analyte volumes that can straightforwardly be extended to sensing at different wavelength ranges, liquid analytes and other spectroscopic techniques with only little adjustments of the device platform.