Low-loss nonvolatile silicon photonic switching enabled by a GST superlattice

Phase-change photonics offers nonvolatile programmability but is often limited by high absorption of crystalline Ge₂Sb₂Te₅ (GST). Here, we demonstrate a low-loss, nonvolatile silicon photonic switching platform enabled by a GST superlattice (GST-SL) integrated on SOI. The GST-SL is constructed by alternating 3 nm GST sublayers and 3 nm SiO₂ spacers, which suppresses the loss penalty in the crystalline state while preserving strong phase-change-induced optical modulation. Using microring-resonator extraction, we obtain attenuation coefficients of 0.0377dB/µm^-1 (amorphous) and 0.2592dB/µm^-1 (crystalline) together with a resonance shift coefficient of 0.0615nm/µm^-1, confirming that the GST-SL architecture enables efficient switching/phase tuning at markedly reduced loss. Electrical driving is implemented with an ITO microheater to access programmed states, providing a practical route toward low-loss nonvolatile elements for scalable programmable PICs.