Optimization and Comparative Analysis of Rectangular and Slot Waveguide based Symmetric Ring and Racetrack Resonators for SoI Photonic Integrated Filters

Over the past decades Silicon on Insulator (SoI) technology has tantalized the interest of researchers in the design of numerous nonlinear Photonic Integrated Circuits (PIC's) to provide a variety of devices. In this manuscript, four different types of optical add/drop resonators are proposed and compared using their simulated microcomb notch filter performance. The four types of resonators are (i) rectangular waveguide based conventional ring resonator, (ii) slot waveguide based ring resonator, (iii) rectangular waveguide based racetrack resonator, and (iv) slot waveguide based racetrack resonator, for variety of active/passive applications. The resonator parameters: Free Spectral Range (FSR), Full Width at Half Maximum (FWHM), Finesse (F) and Quality factor (Q-factor) are evaluated and compared for four resonators. The resonators are optimized for different parameters, such as ring radius (R), gap (g) between the waveguides and coupling length (L-c). The optimized R of similar to 30 mu m with the power coupled 'g' of 55 nm is found after performing rigorous simulations for the entire optical conventional band (C-band) i.e., in 1530 nm - 1565 nm using Finite Element Method (FEM). The manuscript provides valuable insights into the design considerations and performance trade-offs of different optical resonators in PICs showing symmetricity along x-axis and y-axis. These findings can guide the development of efficient and high-performance integrated photonic devices for various applications, including communication and computing systems.