Hybrid WDM/MDM (De) multiplexer based on Fabry–Perot resonators with Bragg grating reflectors

The traveling-wave-like Fabry–Perot (TW-like F-P) resonators, utilizing transverse-mode conversion, have been thoroughly investigated as on-chip filters. However, the asymmetric directional coupling (ADC) between the phase shifter and the output waveguide in this structure is not fully utilized, resulting in a rare implementation of hybrid wavelength division multiplexing (WDM) and mode division multiplexing (MDM). In this paper, using the transfer matrix method (TMM), we investigate methods to effectively enhance the quality factor (Q-factor) of TW-like F-P resonators. This is achieved by increasing the phase shifter length and reducing the coupling coefficient between these waveguides, without significantly impacting the channel drop efficiency. MDM can be achieved by adjusting the width of the output waveguides, utilizing the ADC between the phase shifter and the output waveguide. We design nine-channel hybrid WDM-MDM multiplexers based on TW-like F-P resonators. The variational-finite-difference time-domain (varFDTD) method is utilized to analyze the device’s performance, and its single channel extinction ratio (ER) values can reach −20 dB. This work paves the way for TW-like F-P-resonator-based large capacity optical communications and interconnections.