Compact highly-sensitive device based on interference-whispering gallery mode composite structure

A composite whispering gallery mode (WGM) sensor integrating nonadiabatic tapered optical fiber interference (NTFI) was first proposed and fabricated for humidity sensing applications. The microbottle resonator is a compact, composite all-fiber optic sensor manufactured by coupling a polyvinyl alcohol (PVA)-coated hollow core fiber (HCF) with a nonadiabatic tapered single mode fiber (SMF). Rather than merely connecting interference structure and WGM cavity in series, the sensor exploits interference and WGM resonance within the same optical fiber pathway, which has the advantages of extremely high detection limit and resolution advantages. Experimental results demonstrate that the composite sensor possesses a humidity sensitivity of -59.9 pm/%RH. Compared with the traditional cascade microcavity, the sensor boasts advantages including simple fabrication, low cost, compact size, and excellent stability, rendering it highly beneficial for diverse practical applications, notably in concentration measurements.