Low-energy ultrafast laser-induced GeTe RF switches based on anti-reflection coatings

This work presents a low-energy, ultrafast GeTe radio frequency switch actuated by a nanosecond-pulse laser, with its key innovation being the integration of a tailored anti-reflection coating (ARC) to boost photothermal conversion efficiency. By minimizing optical reflection and confining thermal energy within the GeTe layer, the ARC addresses a critical bottleneck in laser-induced phase change RF switches - high energy consumption due to inefficient light absorption. The ARC is specifically designed to mitigate the high reflectivity of GeTe in both its crystalline and amorphous states. Coupled optical-thermal simulations reveal that a 50 nm silicon nitride ARC reduces the reflectivity of crystalline GeTe at 532 nm from ∼70% to ∼30%, thereby enhancing photothermal conversion efficiency and suppressing heat dissipation. Experimentally, the ARC-coated switch achieves a 36% reduction in switching energy density (from 132 to 84.5 mJ/cm²) during amorphization, with both phase transitions induced by a 10 ns laser pulse. Notably, the ARC integration introduces negligible degradation in RF performance, delivering an ON-state resistance of 4.5 Ω and an OFF-state capacitance of 3 fF, values comparable to those of state-of-the-art GeTe RF switches. This CMOS-compatible, compact device offers promising prospects for low-energy, high-speed, reconfigurable RF front-ends.