Lossless resistive micro-heater design for reconfigurable phase-change photonics

Electrically reconfigurable photonics based on optical phase change materials (PCMs) has attracted surging interest recently, with broad potential applications ranging from analog computing to optical camouflage. PCM switching in these devices is customarily implemented using resistive micro-heaters. These electrically conductive micro-heaters, however, cause significant optical losses due to free carrier absorption. In this paper, we present a design concept that overcomes this limitation without compromising the electrical performance of the micro-heaters. Using doped Si heaters as an example, we show that such parasitic losses can be suppressed by engineering the optical mode to minimize the optical field overlap with the lossy doped region. An active optical meta-grating design was proposed based on the concept, which achieves 2π phase tuning range near 1.53 μm wavelength with only 10 nm thick Sb₂S₃ while maintaining over 85% optical efficiency.