광반응 재료가 코팅된 단주기격자 기반 자외선 센서의 휴대성 및 민감도 향상 연구

Abstract

This study focused on developing an optical sensor that monitors ultraviolet (UV) light. Recently, we proposed and demonstrated a novel, highly sensitive UV sensor based on fiber Bragg grating (FBG). The sensor was coated with an azobenzene polymer material that acts as an UV-induced stretchable functional material in combination with a cylindrical focal lens. The incident UV light is focused on the FBG surface. In this study, we have improved the sensitivity of the sensor by employing a cylindrical focal mirror as a curved reflector to refocus the UV light passing through the FBG. We considered the performance of several different types of reflectors and chose an optimum curvature radius for the reflector. Compared to the UV sensor without an auxiliary device, the sensitivity of the FBG sensor incorporating a focal lens and a curved reflector was 15 times higher. In addition, we also developed a package module to protect the FBG-based device from environmental factors such as temperature and/or flow fluctuation. Subsequently, the module was tested to verify its performance. In previous reports where the FBG sensor was tested, we used individual optical instruments such as a broad-band source and an optical spectrum analyzer. These individual instruments inhibited the implementation of this sensor in industrial fields. For increased portability of the UV sensor, we have developed a single instrument that includes an optical source and a line CCD (charge coupled device) with a diffraction grating to analyze the optical spectrum. In comparison with the previous bulky measurement system, this UV sensing system provides unparalleled performance in terms of mobility and economic efficiency. The system can monitor UV light at multiple regions in four optical channels. For proof-of-concept, we tested the performance of three UV sensors with different center wavelengths placed at different points in series.