Mode-Engineered Metal Microheaters for Low-Loss Nonvolatile Phase-Change Photonics

Nonvolatile tuning based on phase-change materials offers a route to reconfigurable photonics with zero static power, but electrical switching remains limited by available microheaters. Doped-silicon heaters are effective yet lack transferability across broader material platforms and require higher voltages due to built-in potential. We demonstrate a metal microheater architecture utilizing mode engineering to suppress metal-induced loss while preserving efficient thermal access. Using platinum microheaters integrated with Sb2S3-loaded undoped silicon waveguides, we demonstrate low-loss, electrically driven nonvolatile phase tuning. Notably, the device operates with low switching energy of 44.55 μJ (44.41 nJ) and CMOS-compatible voltages of 0.93 V (1.8 V) for crystallization/SET (amorphization/RESET). The device exhibits 0.15 dB/μm propagation loss, 0.25 nm nonvolatile spectral shifts, and >200 reversible switching events. To establish the versatility, we further demonstrate the electrical switching of Ge2Sb2Te5 (GST), a phase-change material with faster kinetics. Our results establish a low-loss, doping-free strategy for nonvolatile programmable photonics.