Microbottle resonator for formaldehyde liquid sensing

We have successfully investigated the use of a whispering gallery mode (WGM) optical micro bottle resonator (MBR) for liquid formaldehyde (CH2O) sensing. The MBR was fabricated via the soften-and-compress method to create a bulge (bottle) structure with a bottle diameter of 190 mu m. The MBR was optically excited by using a non-adiabatic 2 mu m optical microfiber and was found to have a Q-factor of > 10(5). The MBR was then employed to measure formaldehyde concentration within 1-5% range and the performance was compared with a bare microfiber. The MBR sensor was found to have a sensitivity of 4.397 dB/% with 90% linearity which were superior to the bare microfiber. The MBR sensor was also found to have good repeatability and stability over a period of 60 min. This indicates that MBR sensor has a great potential to be employed as a low cost formaldehyde liquid sensor.