On-chip reconfigurable mode converter by rectangle Sb2S3 inlaid in 4H-SiC

Antimony sesquisulfide Sb₂S₃, an emerging low-loss phase change material, has attracted great interest for its unique properties, enabling its huge potential applications in programmable integrated optics. A reconfigurable mode converter is proposed and demonstrated numerically assisted by a rectangle Sb₂S₃ inlaid in a slab 4H-SiC waveguide. A threedimension finite-difference time-domain (3D FDTD) method is employed to simulate and optimize the proposed structure. The TM0-to-TM1 mode conversion is realized with transmittances (T) of 0.91 and mode purity (MP) of 93% at the wavelength of 1550 nm in the crystalline Sb₂S₃ state. When the Sb₂S₃ is switched to the amorphous state, the mode-conversion effect disappears, and the incident TM0 mode propagates unimpededly with T > 0.99 and MP > 97.64% within the waveband from 1500 nm to 1600 nm. The nonvolatile reconfigurable mode converter can contribute to programmable photonic integrated circuits and neuromorphic optical computing.