Abstract
We compare the performance of two whispering gallery mode optical resonators; optical micro-ball (MBaR) and micro-bottle resonators (MBR) as a relative humidity (RH) sensor. The MBaR and MBR are fabricated via the so-called "soften-and-compress" method to create a ball or bulge structure. The MBaR and MBR is then optically excited by using a 8 mu m optical microfiber and was found to have a Q-factor of >105. The MBaR and MBR was then employed as a humidity sensor with a RH range of between 40% to 100% and the performance is compared for both resonator. The MBR RH sensor was found to have a sensitivity of 0.2973 dB/%, linearity >90% and is superior to the MBaR microfiber in all measured parameters. The MBR RH sensor was also found to have good repeatability and stability compare to MBaR.