Mid-infrared electro-optic modulation by phase-change materials driven by transparent MEMS microheaters

Non-volatile phase-change materials (PCMs) provide a promising material platform to design reconfigurable electro-optic devices. However, for PCM-based spatial light modulators, electro-optic switching of material phases by a voltage pulse is generally affected by the filamentation effect. An alternative way to induce phase transition and reversible modulation is by on-chip micro-heaters, whereas these microheaters can only reflect light where noble metals are generally used as thermal resists. Moreover, the corresponding power consumption is very high because most heat energy dissipates into substrates, preventing the compact integration of PCM-based micro-modulators into the miniaturized and reconfigurable optical chip-array systems. Here, we propose a PCM electro-optical modulator working on the transmission mode with MEMS microheaters. The heating circuit is fabricated on a 200-nm-thick free-standing Si3N4 film, and transparent conductive oxides are used as thermal resists to allow light transmission. According to multi-physics simulations, the proposed MEMS modulators can make a thermal hotspot up to 400 °C in just 100 μs at 2 V bias voltage, indicating low power consumption. Meanwhile, by changing the phase state of PCM from amorphous to crystalline, the mid-infrared light transmission can switch from 0.71 to near zero in the mid-infrared range. The proposed MEMS modulators could inspire new applications in reconfigurable phase-change nanophotonics.