Light-Driven Thermo-Optical Effects in Nanoresonator Arrays

Thermonanophotonics, that is the study of photothermal effects in optical nanoantennas, has recently attracted growing interest. In particular, going beyond thermoplasmonic designs, thermo-optical modulation of dielectric nanoantennas opens new opportunities for reconfigurable and non-reciprocal metasurfaces. However, understanding light-driven thermo-optical effects in large arrays of nanoantennas remains challenging. In this work, for the first time the impact of thermo-optical effects beyond the single nanoresonator is analyzed. By performing photo-thermo-optical computations of large nanoantenna arrays (more than 105 elements), the complex interplay of thermo-optical effects with self- and collective-heating in 1D, 2D, and 3D systems are explored. The results show that collective heating contributions strongly alter the local absorption cross-section and, in return, also the self-heating term. Therefore, both terms must be carefully accounted for in large arrays. Importantly, by controlling the nanoresonator size, array periodicity and illumination wavelength, thermo-optical effects enable the realization of non-trivial spatial temperature profiles. In particular, ways to counteract collective heating effects and obtain flat temperature profiles in 2D arrays of dissimilar silicon nanoresonators are demonstrated. Overall, this work paves the way to the design of light-driven reconfigurable metasurfaces, supporting the development of advanced thermonanophotonic functionalities.