A New Strategy for Real-Time Humidity Detection: Polymer-Coated Optical Waveguide Sensor

Abstract

This paper proposes a novel strategy for low humidity detection, an optical waveguide (OWG) sensor that is locally coated with polyvinylpyrrolidone (PVP) film. The humidity sensor was fabricated using a spin coating on a K+-exchanged glass optical waveguide with PVP film. Its sensing properties were investigated by injecting a humid air range of 10.6~32%RH (relative humidity) at room temperature. The surface morphology of the PVP film was characterized by an atomic force microscope (AFM). The possible humidity sensing mechanism of the proposed sensor was discussed by using absorption spectra. This study showed that the PVP-coated OWG sensor possessed high sensitivity, stability, and rapid response/recovery. Therefore, these observed results demonstrate that the low-cost OWG humidity sensor could be applied in real-time low concentration water vapor monitoring.