Modeling and performance evaluation of in-line Fabry-Perot photothermal gas sensors with hollow-core optical fibers
Abstract
We study photothermal phase modulation in gas-filled hollow-core optical fibers with differential structural dimensions and attempt to develop highly sensitive practical gas sensors with an in-line Fabry-Perot interferometer for detection of the phase modulation. Analytical formulations based on a hollow-capillary model are developed to estimate the amplitude of photothermal phase modulation at low modulation frequencies as well as the -3 dB roll-off frequency, which provide a guide for the selection of hollow-core fibers and the pump modulation frequencies to maximize photothermal phase modulation. Numerical simulation with the capillary model and experiments with two types of hollow-core fibers support the analytical formulations. Further experiments with an Fabry-Perot interferometer made of 5.5-cm-long anti-resonant hollow-core fiber demonstrated ultra-sensitive gas detection with a noise-equivalent-absorption coefficient of 2.3×10−9 cm-1, unprecedented dynamic range of 4.3×106 and <2.5% instability over a period of 24 hours.
- Publication:
-
Optics Express
- Pub Date:
- February 2020
- DOI:
- 10.1364/OE.385670
- Bibcode:
- 2020OExpr..28.5423B