Symmetric mode multiplexing waveguide switch based on optical phase change material

We propose a 2×6 mode-multiplexing silicon optical waveguide switch leveraging the low-loss phase-change material Ge2Sb2Se4Te1. The device architecture comprises a 2×2 symmetric switch cascaded with two 1×3 reconfigurable mode switches. The design is analyzed using coupled mode and supermode theories, with propagation characteristics verified via three-dimensional finite-difference time-domain simulations. Our results demonstrate robust performance across the optical communication C-band. At 1550 nm, the 2×2 switching element exhibits a high extinction ratio (ER) of 37 dB and a minimal insertion loss (IL) of 0.03 dB. The 1×3 components facilitate efficient mode conversion from TE0 to TE1 and TE2, yielding an ER and IL of 17.2 and 0.15 dB for the former and 16.19 and 0.71 dB for the latter. The integrated 2×6 switch enables both time division and reconfigurable mode-multiplexing, maintaining an ER>12.5 dB and IL<1.8 dB across all 12 operational channels. Furthermore, through geometric optimization, the device effectively isolates and selects modes from mixed transverse electric (TE) or transverse magnetic (TM) inputs. This multi-channel waveguide switch significantly enhances the versatility of reconfigurable, phase-change-material-based multiplexing for integrated photonic circuits.