Compact reconfigurable on-chip polarization beam splitters enabled by phase change material.

In this paper, we present the design of a compact reconfigurable polarization beam splitter (PBS) enabled by ultralow-loss phase-changing Sb2Se3. By harnessing the phase-change-mediated mode coupling in a directional coupler (DC), guided light with different polarizations could be routed into different paths and this routing could be dynamically switched upon the phase change of Sb2Se3. With an optimized DC region, the proposed PBS demonstrates efficient polarization splitting with crosstalk less than -21.3 dB and insertion loss less than 0.16 dB at 1550 nm for both phase states of Sb2Se3, and features energy efficient property benefitting from the nonvolatile phase change of Sb2Se3, which holds great potentials for on-chip applications involving polarization control, including polarization-division multiplexing system, quantum photonics, microwave photonics, etc.

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 Ge2Sb2Te5) 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 Sb2S3 integrated inside the slot region. The MSW supports two lowest order TE modes, i.e., symmetric TE00 and antisymmetric TE01 modes, and the phase of Sb2S3 could actively tune two-mode interference behavior. Owing to the enhanced electric field in the slot, the interaction strength between modal field and Sb2S3 could be boosted, and a photonic switch containing a ∼9.4 µm-long Sb2S3-MSW hybrid section could effectively alter the light transmission between bar and cross ports upon the phase change of Sb2S3 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) Sb2S3 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.