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

Thermal tuning of the optical refractive index in thewaveguidesto control light phase accumulation is essential in photonic-integratedsystems and applications. In silicon photonics, microheaters are mainlyrealized by metal wires or highly doped silicon lines, placed at asafe distance (similar to 1 mu m) from the waveguide to avoid considerableoptical loss. However, this poses a significant limitation for heatingefficiency because of the excessive free-carrier loss when a heateris brought closer to the optical path. In this work, we present anew concept of using optically transparent 2D semiconductors (e.g.,MoS2) for realizing highly efficient waveguide-integratedheaters operating at telecom wavelengths. We demonstrate that a single-layerMoS(2) heater with negligible optical absorption in the infraredcan be placed in close proximity (only 30 nm) to the waveguide andshow the best-reported power consumption of P (pi) similar to 7.5 mW for waveguide-integrated heaters (nothermal insulations) without sacrificing the optical insertion loss.The heater's response time is similar to 25 mu s, which islimited by the Au/1L-MoS2 Schottky contact. Both the efficiencyand response time can be further significantly improved by realizing2D MoS2 heaters with Ohmic contacts. Our work shows clearadvantages of employing 2D semiconductors for heater applicationsand paves the way for developing novel energy-efficient loss-less2D heaters for on-chip photonic-integrated circuits.