Whole-circuit integration of low-loss phase-change materials for reconfigurable silicon photonics

The integration of low-loss phase-change materials (PCMs) with silicon photonics has attracted increasing interest for reconfigurable and non-volatile photonic devices. However, most existing approaches selectively pattern PCM regions through additional lithography and lift-off processes. Here, we propose a whole-circuit integration approach to simplify the fabrication of PCM-based silicon photonic devices, where a PCM thin film is deposited on a silicon-on-insulator (SOI) wafer and co-etched with a silicon layer. Using low-loss Sb₂Se₃, the additional propagation loss is limited to ∼0.78 dB/mm. Meanwhile, whole-circuit integration provides a modulation region far exceeding selective integration. A full 2<i>π</i> multi-level phase modulation is experimentally demonstrated in an unbalanced Mach-Zehnder interferometer (UMZI). These results establish whole-circuit PCM integration as a scalable and foundry-compatible route toward programmable silicon photonic circuits.