Ultrasensitive Gas Detection via Polarization-Mode Photothermal Interferometry in a Single-Mode Nanofiber Coupler.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41629067.
- Also identified by DOI 10.1021/acs.nanolett.5c06094 and PMC identifier 12922175.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Optical nanofibers (ONF) have emerged as versatile platforms for studying light-gas interactions at the micro/nanoscale, yet existing ONF gas sensors remain limited in detection sensitivity. Here, we report a polarization-mode photothermal interferometry technique that precisely measures the gas absorption-induced phase difference between two polarization states of the symmetric supermode of a single-mode ONF coupler. The high power density and large evanescent field associated with the ONF coupler enhance the efficiency of photothermal phase modulation, while the strong waveguide birefringence and noise-immune differential phase detection confer environmental immunity, jointly yielding an order-of-magnitude enhancement in the signal-to-noise ratio. With a 2 cm-long overcoupled ONF coupler, we achieved an acetylene detection limit of 6 ppb and an instability below ± 1.2% over 30 h. This compact ONF gas sensor, based on standard fused directional coupler technology, provides a promising route toward cost-effective and high-performance solutions for environmental monitoring and industrial applications.