Optically Transparent and Thermally Efficient 2D MoS₂ Heaters Integrated with Silicon Microring Resonators

Thermal tuning of the optical refractive index in the waveguides to control light phase accumulation is essential in photonic-integrated systems and applications. In silicon photonics, microheaters are mainly realized by metal wires or highly doped silicon lines, placed at a safe distance (∼1 μm) from the waveguide to avoid considerable optical loss. However, this poses a significant limitation for heating efficiency because of the excessive free-carrier loss when a heater is brought closer to the optical path. In this work, we present a new concept of using optically transparent 2D semiconductors (e.g., MoS₂) for realizing highly efficient waveguide-integrated heaters operating at telecom wavelengths. We demonstrate that a single-layer MoS₂ heater with negligible optical absorption in the infrared can be placed in close proximity (only 30 nm) to the waveguide and show the best-reported power consumption of P_π ∼ 7.5 mW for waveguide-integrated heaters (no thermal insulations) without sacrificing the optical insertion loss. The heater’s response time is ∼25 μs, which is limited by the Au/1L-MoS₂ Schottky contact. Both the efficiency and response time can be further significantly improved by realizing 2D MoS₂ heaters with Ohmic contacts. Our work shows clear advantages of employing 2D semiconductors for heater applications and paves the way for developing novel energy-efficient loss-less 2D heaters for on-chip photonic-integrated circuits.