Abstract
Whispering gallery mode (WGM) resonators are versatile high sensitivity sensors, but applications regularly suffer from elaborate and expensive manufacturing and read-out. We have realized a simple and inexpensive concept for an all-polymer WGM sensor. Here, we evaluate its performance for relative humidity measurements demonstrating a sensitivity of 47 pm/% RH. Our results show the sensor concepts’ promising potential for use in real-life applications and environments.
Highlights
Monitoring and measuring the relative humidity (RH) is an important factor in many chemical processes and industrial applications, for example in air quality management, food manufacturing or in metal processing and polymer synthesis [1]
Optical humidity sensors are based on radiation losses in optical waveguides [4], fiber Bragg gratings (FBGs) [5,6] or whispering gallery modes (WGMs), for example [7]
Different variants of the sensor array were investigated to evaluate the performance of the polymer-based WGM sensor concept for measurement of relative humidity
Summary
Monitoring and measuring the relative humidity (RH) is an important factor in many chemical processes and industrial applications, for example in air quality management, food manufacturing or in metal processing and polymer synthesis [1]. There is a wide range of different possibilities for humidity detection based on electrical, as well as optical principles [2]. Optical humidity sensors are based on radiation losses in optical waveguides [4], fiber Bragg gratings (FBGs) [5,6] or whispering gallery modes (WGMs), for example [7]. When using a radiation loss-based sensor, it is difficult to separate the response of the sensor to humidity from changes in laser power and varying losses in optical connectors. Silica-based FBGs need a humidity-sensitive polymer coating to be functional. This coating material swells in response to humidity and reduces the refractive index, leading to a change of the
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