Reconfigurable inverse-designed multifunctional photonic device based on phase change material Sb₂Se₃

Reconfigurable, programmable and compact devices hold immense importance in high-density programmable photonicintegrated circuits (PICs) used in optical communications and signal processing. Compared with traditional methods of designing devices, the inverse design approach provides a new avenue for achieving high-density PICs. However, the majority of programmable photonic systems result in large footprints and high energy consumption due to the relatively weak modulation capability. This severely limits high-density integration of on-chip photonic systems. In recent years, chalcogenide phase-change materials (PCMs) have emerged as a promising alternative for achieving reconfigurable photonic devices by utilizing their high refractive index contrast and reversible phase transition between amorphous and crystalline states. In this work, we demonstrate a 1 × 2 multifunctional and compact photonic device based on phasechange material Sb2Se3 with footprints of only 4.8 × 4.8 μm2. We adopt the adjoint optimization approach to design the Sb2Se3 film on the silicon 3dB power splitter designed in advance. Subsequently, we can use laser heating technique to change the phase patterns on the Sb2Se3 film to achieve the designed device function. This enables the device to be reconfigurable from an optical switch to an arbitrary ratio power splitter. Remarkably, the functionality of our photonic device is rewritable, allowing for the erasure and reconfiguration of the Sb2Se3 phase pattern. The demonstrated programmable phase-change photonic devices will significantly enhance the flexibility of photonic devices and promote the development of high-density programmable PICs.