Quasi Gradient‐Free Temperature Control in Micro and Nano Systems for Large‐Scale Thermoplasmonic Applications

Abstract Gaining accurate control over surface temperature is vital in optoelectronics, photocatalysis, and biosensing. Thermoplasmonic techniques excel in regulating surface temperature, offering exceptional spatial resolution and thermal control. While most efforts focus on designing nanoscale temperature patterns via efficient light‐to‐heat conversion, an alternative: engineering thermal conductivity profiles around nanoantennas is explored to give an additional temperature control knob. In this work, the thermoplasmonic performance of regular gold nanoantennas has been optimized by the generation of an anisotropic thermal conductivity substrate. This consists of a thin film of silicon grown on a silica substrate where the heat generated at the nanoantennas can be diffused in‐plane along the silicon layer while it is confined out‐of‐plane by the silica. the potential of this approach is numerically demonstrated for the design of temperature gradients by means of metasurfaces. Experimentally, the generation of homogeneous temperature patterns with the capability of diffusing heat away is demonstrated from the thermoplasmonic source. This makes a difference with respect to most approaches in literature where the shape of the thermal patterns is necessarily determined by the nanoantenna distribution. In addition, it shows the potential of this approach in applications that may require a large surface area of operation.