Photonic-crystal-based hybrid wavelength-mode division multiplexer for SOI platforms

Abstract

This paper presents a 12-channel hybrid wavelength-mode division multiplexer (WDM-MDM) based on 2D photonic crystals. The proposed device consists of microring resonators (MRRs) and asymmetric directional couplers (ADCs) to perform three-channel wavelength division multiplexing and four-channel mode division multiplexing operations, respectively. Each MRR can work bi-directionally, providing the same wavelength channels separately in two drop ports. The bus waveguides in the cascaded ADCs are optimized to convert the fundamental modes to the corresponding higher-order modes and are connected through taper regions for the smooth transition of modes. The designed device is simulated using the finite-difference time-domain solver, achieving a maximum channel spacing and insertion loss of 5.05 nm and 0.97 dB, respectively. The device size of the proposed WDM-MDM is 74.98µm×32.82µm. The fabrication tolerance study is performed for uniform over-etch and under-etch conditions. The temperature tolerance study on the resonant wavelength is performed, and the temperature coefficient shift of <0.0254nm/K is achieved. The proposed device can potentially increase the channel capacity for on-chip high-density optical interconnects.