Terahertz whispering gallery mode resonators: influence of geometric properties on spectral performance for sensing applications

Terahertz Whispering Gallery Mode Resonators (WGMRs) have granted great interest in the photonic regime. They are characterized by their high-quality factor, providing an excellent chance for integrated photonic systems. The geometry of the WGMR plays a crucial role in optimizing spectral properties for specific applications. In the presented study, first, the mode analysis is done using the Finite Element Method (FEM) to investigate the spatial field distribution of a microsphere WGMR of a selected radius of 40 mu m. A theoretical investigation is also performed to study the impact of microsphere radius on key spectral properties, including free spectral range (FSR), quality factor, model number, and resonance frequency. The radius of delivery fiber is fixed to 1 mu m, while the radius of the microsphere is varied between 25 and 100 mu m. According to this study, a small microsphere radius results in a large FSR and high-quality factor (Q(F)) 10(12), enabling enhanced sensitivity, considered an essential requirement of THz WGMR sensors.