Simulation of Optical Hollow Microbottle Resonator for Sensing Applications

A silica hollow microbottle resonator (HMBR) combined with a pair of curved silicon micro-mirrors on the outside wall of the microbottle is proposed and numerically investigated using the Finite-Difference Time-Domain (FDTD) algorithm. The microbottle has only 32 μm length, 26 μm width and 1.5 μm wall thickness. The curved micro-mirrors overcome the light diffraction loss through light focusing, while the microbottle, in which gas analytes are introduced, provides additional light confinement and hence improves the performance of the sensor. The obtained Q -factor is about 4590 at 1543.21 nm and the free spectral range (FSR) is more than 31 nm. An internal sensitivity of 1567 nm per refractive index unit (RIU) is achieved in the near-infrared (NIR), which is the highest ever reported for an refractive index (RI) gas sensor based on HMBR. With the introduction of an air gap layer between the silica HMBR and the silicon micro-mirrors, both the Q -factor and sensitivity have been improved to 6729 and 1730 nmRIU − 1 respectively. We believe that the proposed architecture will be used in future sensing applications.