  Thermonanophotonics, i.e. the study of photothermal effects in optical
nanoantennas, has recently attracted growing interest. While thermoplasmonic
structures enable a broad range of applications, from imaging and optofluidics
devices to medical and photochemical systems, dielectric nanoantennas open new
opportunities for thermo-optical modulation and reconfigurable metasurfaces.
However, computing both photo-thermal and thermo-optical effects in large
arrays of nanoantennas remains a challenge. In this work, we implement a fast
numerical method to compute the temperature increase of multi-dimensional
arrays of optical antennas embedded in a uniform medium, accounting for
self-heating, collective heating as well as thermo-optical effects. In
particular, we demonstrate scalable computation of temperature in 3D networks
with $10^5$ particles in less than 1 hour. Interestingly, by explicitly
considering the role of discrete nanoparticles on light attenuation and
photothermal conversion, this approach enables the optimization of complex
temperature profiles in 3D arrays. Importantly, we compute for the first time
the impact of thermo-optical effects beyond the single nanoantenna. Our results
show that collective heating contributions amplify these effects in
multi-dimensional arrays of both Silicon and Gold nanospheres, highlighting the
importance of considering them in photothermal calculations. Overall, the
proposed method opens new opportunities for the rapid assessment of complex
photothermal effects in arrays of optical nanoantennas, supporting the
development of advanced thermonanophotonic functionalities.
