Acrylate/GO composite film enabled optical microcavity relative humidity sensor with enhanced sensitivity by pump-detection technique

An acrylate/graphene oxide (GO) composite film enabled optical microcavity relative humidity (RH) sensor with enhanced sensitivity by pump-detection technique is presented. An acrylate/GO composite film serves as both the sensitive film and reflection film of an open optical microcavity, which is fabricated by 3D printing on the end face of a single-mode fiber. A pump-detection technique is used to improve the sensitivity of the sensor. Experimental results show that its sensitivity is only 151.11 p.m./%RH without the 980-nm pump light. In contrast, its sensitivity is significantly improved after introducing the 980-nm pump light, and its sensitivity reaches 2.4 times as much as that of the unpumped sensor. Moreover, it exhibits fast response characteristics with humidity response time and recovery time of 0.32 s and 1.40 s, respectively. In real-world application tests, the sensor effectively distinguishes normal, rapid, slow, and apnea breathing patterns, demonstrating strong potential for medical and sports-related respiratory monitoring.