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

• Main Authors: Md Johari, Md Ashadi, Jali, Mohd Hafiz, Abdul Khudus, Muhammad Imran Mustafa, Al Noman, Abdullah, Wadi Harun, Sulaiman
• Format: Article
• Language: English
• Published: Elsevier GmbH 2019
• Online Access: http://eprints.utem.edu.my/id/eprint/24205/2/WHISPERING%20GALLERY%20MODES%20ON%20OPTICAL%20MICRO-BOTTLE%20RESONATOR%20FORHUMIDITY%20SENSOR%20APPLICATION.PDF; http://eprints.utem.edu.my/id/eprint/24205/; https://www.sciencedirect.com/science/article/pii/S0030402619304127; https://doi.org/10.1016/j.ijleo.2019.03.111

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 Db = 190μm, stem diameter of Ds = 125μm and bottle length of Lb = 182μm. The MBR is then optically excited by using a 2 μm optical microfiber and was found to have a Q-factor of > 104. 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 > 105 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