All‐Dielectric Photo‐Thermo‐Optical Metasurfaces for Thermal Landscaping at the Nanoscale

Precise control of temperature fields at the micro‐ and nanoscale is essential for emerging applications in nanophotonics, catalysis, and microfluidics, yet remains difficult due to the diffusive nature of heat. While inverse‐design algorithms have advanced thermoplasmonic metasurfaces, their extension to all‐dielectric systems has not been explored. Here, an inverse thermal design framework is introduced for dielectric metasurfaces composed of thermo‐optical amorphous silicon (a‐Si) nanoresonators. By leveraging a precomputed library of absorption spectra as a function of geometry and temperature, target thermal profiles are directly mapped onto metasurfaces, enabling both uniform and complex temperature shaping. Unlike plasmonic platforms that require multi‐resonator unit cells for tunability, dielectric nanoresonators provide intrinsic reconfigurability. At wavelengths where the thermo‐optical coefficient is negligible (e.g., ∼500 nm), absorption remains temperature‐invariant, whereas at other wavelengths it becomes strongly temperature‐dependent, allowing illumination intensity to reshape the thermal landscape. This multifunctionality permits a single metasurface to yield distinct profiles under different excitation conditions without added structural complexity. As a proof of concept, photothermal catalysis on such metasurfaces is modeled, predicting over 30% enhancement in reaction rates. The presented framework establishes a scalable strategy for engineering nanoscale temperature fields with broad implications for catalysis, thermal management, and photothermal energy conversion.