Compact nonvolatile 2×2 photonic switch based on two-mode interference.

On-chip nonvolatile photonic switches enabled by phase change materials (PCMs) are promising building blocks for power-efficient programmable photonic integrated circuits. However, large absorption loss in conventional PCMs (such as GeSbTe) interacting with weak evanescent waves in silicon waveguides usually leads to high insertion loss and a large device footprint. In this paper, we propose a 2×2 photonic switch based on two-mode interference in a multimode slot waveguide (MSW) with ultralow loss SbS integrated inside the slot region. The MSW supports two lowest order TE modes, i.e., symmetric TE and antisymmetric TE modes, and the phase of SbS could actively tune two-mode interference behavior. Owing to the enhanced electric field in the slot, the interaction strength between modal field and SbS could be boosted, and a photonic switch containing a ∼9.4 µm-long SbS-MSW hybrid section could effectively alter the light transmission between bar and cross ports upon the phase change of SbS with a cross talk (CT) less than -13.6 dB and an insertion loss (IL) less than 0.26 dB in the telecommunication C-band. Especially at 1550 nm, the CT in the amorphous (crystalline) SbS is -36.1 dB (-31.1 dB) with a corresponding IL of 0.073 dB (0.055 dB). The proposed 2×2 photonic switch is compact in size and compatible with on-chip microheaters, which may find promising applications in reconfigurable photonic devices.