Fiber-based optical Fabry-Perot gas sensor for fast and on-column detection

A versatile, compact, and sensitive fiber-based optical Fabry-Perot (FP) gas sensor is reported in this paper. The sensor probe is composed of a silver layer and a vapor-sensitive polymer layer that are deposited on the cleaved fiber endface to form an FP cavity sequentially. The interference spectrum generated from the reflected light at the silver-polymer and polymer-air interfaces changes upon the absorption of gas analytes. This structure enables using polymer of any refractive index (RI) as the sensing layer, which significantly enhances the sensor versatility. Two polymers of polyethylene glycol (PEG) 400 (RI=1.465-1.469) and Norland Optical Adhesive (NOA) 81 (RI=1.53-1.56) are used as the gas sensing polymer to demonstrate the feasibility of the FP sensor, and show drastically different sensor response to various gas analytes. In addition, we assemble the FP sensor with a short fused silica capillary into a sensor module, and employ it in the gas chromotgraphy (GC) system to investigate its capability as a GC detector for rapid on-column detection.