Optical Heating Bistability in Dielectric Subwavelength Mie-Resonator

Mor Pal Vikram^1*, Te-Hsin Yen¹, Wei-Chun Chao¹, Kentaro Nishida¹, Junichi Takahara^2,3, Shi-Wei Chu^1,4,5

¹Department of Physics, National Taiwan University, Taipei, Taiwan
²Graduate School of Engineering, Osaka University, Osaka, Japan
³Photonics Center, Graduate School of Engineering, Osaka University, Osaka, Japan
⁴Molecular Imaging Center, National Taiwan University, Taipei, Taiwan
⁵Brain Research Center, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Mor Pal Vikram, email:d09222024@ntu.edu.tw

Optical heating in resonant nanostructures is a key phenomenon in nanophotonics, influencing device performance as either a limiting factor or a functional asset, depending on the application context. Recent advances in thermo-photonics, utilizing wavelength-scale optical elements, have highlighted the importance of nonlinear heating effects in nanostructures and metasurfaces. While high-quality factor (high-Q) modes in metasurfaces and bound states in the continuum offer strong field confinement, their limited absorption constrains efficient photothermal conversion. While in low-quality factor (low-Q) resonances with broader linewidths, enhances radiative coupling and absorption, enabling substantial temperature rises even in low-loss dielectrics. Despite this potential, nonlinear heating dynamics in low-Q systems remain largely unexplored. Here, we theoretically and experimentally demonstrate pronounced thermal transitions in silicon nanostructures under high-intensity illumination, characterized by large modulation temperature escalation and bistable heating responses. A coupled theoretical framework incorporating photothermal conversion and thermal feedback successfully explains these dynamics. Our results reveal previously uncharted bistable photothermal behavior, offering opportunities for photothermal optical switching, thermally reconfigurable nanophotonic devices, and advanced thermal microscopy.

Keywords: Optical Heating, Mie-Resonance, Silicon Nanostructures, Raman Nanothermometry, Thermal Bistability