Thermo-Optic Tuning of Mie Resonances in Silicon Nanospheres in the Visible Range

The thermo-optical behavior of crystalline silicon nanospheres (Si NSs) exhibiting Mie resonances in the visible range was investigated. The temperature rise of a Si NS exhibited a nonlinear dependence on the input laser power, arising from the temperature-dependent absorption efficiency due to the thermo-optical effect on the complex refractive index. By employing this effect, active modulation of the scattering spectra was achieved through optical heating, with modulation depths reaching up to 69% at 650 nm and stable performance maintained over 50 switching cycles. The optical properties of the Si NSs remained unchanged even at temperatures of >600 °C, demonstrating their excellent thermal stability. Based on the properties, simulations were performed for Si NS square arrays, which demonstrated significant transmittance modulation by temperature-dependent shifts in the lattice resonances. These findings establish a foundation for thermally reconfigurable all-dielectric metasurfaces for their potential applications in optical modulation, sensing, and adaptive photonic systems.