1 × 2 Switchable Dual-Mode Optical 90° Hybrid Device Based on Thermo-Optic Phase Shifters and 2 × 2 MMI Couplers on SOI Platform

This paper designs a 1 × 2 switchable dual-mode optical 90° hybrid device on the silicon-on-insulator (SOI) platform for the mode division multiplexing hybridized coherent transmission systems in optical communication. Our proposed hybrid uses various 2 × 2 multimode interference (MMI) couplers, symmetric Y-junctions, and thermo-optic phase shifters. The suggested hybrid device working principle is proved on theoretical analysis about the multimode interference and the transfer matrix relation. The optimization of geometrical parameters and metallic micro-heaters is executed through the numerical simulation method. The proposed hybrid coupler expresses lots of optical performance advantages, with an insertion loss lower than 2.5 dB, a common-mode rejection ratio (CMRR) better than -24 dB, and phase error smaller than 4° in the 50-nm wavelength bandwidth of the third telecom window for both two TE modes. Besides, the device is proven large geometrical tolerances in terms of width and height tolerances larger than ±50 nm and ±6 nm in the 1.5-dB variation limit of transmission, respectively. In addition, the proposed device attains relatively low power consumption under 75 mW and an ultrafast switching time below 10 μs. Such advantages of good performances make the device a promising potential for broadband and intra-chip MDM-hybridized coherent optical communication systems and photonic integrated circuits.