Optical hydrogen sensor based on PDMS-formed double-C type cavities with embedded Pt-loaded WO3/SiO2

An optical hydrogen sensor based on PDMS-formed double-C type cavities with embedded Pt-loaded WO3/SiO2 has been proposed. The sensor is fabricated by fusion splicing a single-mode fiber (SMF) with a short segment of hollow-core fiber (HCF), the total length is only similar to 123 mu m. The HCF is separated into the double-C type cavities by a PDMS film, inner C-type cavity forms a micro-cavity Fabry-Perot interferometer (FPI) while outer C-type cavity with embedded Pt-loaded WO3/SiO2 powder serves as a sensitive area. When the sensor is exposed to air mixed with hydrogen, redox reactions result in an increase in ambient temperature leading to the length change of the micro-cavity due to the thermal expansion of the PDMS. The hydrogen sensitivity is -15.14 nm/% within the hydrogen concentration range of 0%-1%. The response time is short, similar to 23 s. The sensor is compact, high sensitivity, fast response. Most of all, the novel double-C type structure effectively solves the problem that sensitive material falls off easily, so it can be long-term used and has great application potential.