1 × N (N = 2, 4) dual-mode optical switch based on multimode interference coupler

Abstract

This paper presents the design and demonstration of 1 × N (N = 2, 4) dual-mode optical switches on a silicon-on-insulator platform, optimized for mode division multiplexing (MDM). The switches utilize a multimode interference-based Mach-Zehnder interferometer combined with thermo-optic phase shifters for efficient mode control. For the elementary 1 × 2 switch, an insertion loss of less than 0.06 dB for the TE₀ mode and 0.10 dB for the TE₁ mode is achieved within the C-band, with crosstalk levels below − 30.5 dB for both modes. Scalability is demonstrated with a 1 × 4 switch, where the insertion loss is reduced to 0.61 dB for TE₀ and 0.48 dB for TE₁, and crosstalk is kept below − 37.9 dB for TE₀ and − 35.5 dB for TE₁ across all switching configurations. The switches are designed using the Lumerical Heat Solver module and the Eigenmode expansion method. With compact footprints of 6.5 × 750 μm² for the 1 × 2 switch and 15 × 1400 μm² for the 1 × 4 switch, these switches offer significant potential for intra-chip MDM systems and photonic integrated circuits.