0000000000374711
AUTHOR
Pauls Kristaps Reinis
High-Sensitivity Whispering Gallery Mode Humidity Sensor Based on Glycerol Microdroplet Volumetric Expansion
We demonstrate a highly sensitive whispering gallery mode (WGM) relative humidity (RH) sensor based on a glycerol microdroplet. WGMs were excited using a 760 nm tunable semiconductor laser. We used free space coupling, which is effective when using a liquid resonator. A detailed analysis of different parameters influencing the sensor’s characteristics (sensitivity, hysteresis, resolution, stability, and temperature) is presented. The sensitivity of the sensor is one of the highest reported (2.85 nm/% RH in the range 50–70% RH with the resolution 1 × 10−4% RH). This type of humidity sensor has several advantages, such as high sensitivity, extended lifetime, good repeatability, and low cost, …
Mode family analysis for PMMA WGM micro resonators using spot intensity changes
The whispering gallery modes (WGM) micro resonators are based on elliptical objects, which can be made from optically transparent materials, The geometry of the object enables optical wave circulating inside the ellipse using total internal reflection. If there is a monochromatic light source with constant intensity to the ellipse, constructive interference may be observed. Poly methyl methacrylate acrylic (PMMA) WGM micro resonators are commercially available with typical optical quality factor of 103-104. These could limit problems with WGM micro resonator expensive manufacturing. Thanks to advances in high resolution image processing, read-outs using spectroscopy (single photo detector) …