Compact Nonvolatile Reconfigurable Mode Converter by SbS Embedded in 4H-Silicon-Carbide-on-Insulator Platform.

Nonvolatile switching is emerging and shows potential in integrated optics. A compact nonvolatile reconfigurable mode converter implemented on a 4H-silicon-carbide-on-insulator (4H-SiCOI) platform with a footprint of 0.5 × 1 × 1.8 μm is proposed in this study. The functional region features an SbS film embedded in a 4H-SiC strip waveguide. The functionality is achieved through manipulating the phase state of the SbS. The high refractive index contrast between the crystalline SbS and 4H-SiC enables high-efficiency mode conversion within a compact footprint. The incident TM0 mode is converted to the TM1 mode with a high transmittance () beyond 0.91 and a mode purity () over 91.72% across the 1500-1600 nm waveband. Additionally, when the SbS transitions to its amorphous state, the diminished refractive index contrast efficiently mitigates the mode conversion effect. In this state, the TM0 mode propagates through the functional region with minimal perturbation, exhibiting ≥ 0.99 and ≥ 97.65% within a 1500-1600 nm waveband. Furthermore, the device performances were investigated under partially crystallized states of SbS. The proposed structure offers a broad range of transmittance differences (-16.42 dB ≤ Δ ≤ 17.1 dB) and mode purity differences (-90.91% ≤ Δ ≤ 96.11%) between the TM0 mode and TM1 mode. The proposed device exhibits a high robustness within ±20 nm Δ and ±10 nm Δ. We believe that the proposed multi-level manipulation can facilitate a large communication capacity and that it can be deployed in neuromorphic optical computing.