Whispering gallery modes on optical micro-bottle resonator for humidity sensor application

摘要

We investigate the use of a class of whispering gallery mode optical resonators, namely, optical microbottle resonators (MBR) as a relative humidity (RH) sensor. The MBR is fabricated via the so-called "soften-and-compress" method to create a bulge (bottle) structure with a bottle diameter D-b = 190 mu m, stem diameter of D-s = 125 mu m and bottle length of L-b = 182 mu n. The MBR is then optically excited by using a 2 gm optical microfiber and was found to have a Q-factor of > 10(4). The MBR was then employed as a humidity sensor with a RH range of between 40%-80% and the performance is compared with a no-MBR microfiber. The MBR RH sensor was found to have a sensitivity 0.0487 dB/%, linearity > 90% and P-value > 10(5) and is superior to the no-MBR microfiber in all measured parameters. The MBR RH sensor was also found to have good repeatability and stability over a period of 60 s. The wavelength shifted for the MBR is 0.03 nm greater than no-MBR.