All-optical transmission control via degenerate quadrupole modes in silicon metasurfaces

We demonstrate an all-optical method for transmissivity control in silicon metasurfaces, overcoming the tradeoff between absorption for photothermal heating and scattering intensity. By leveraging interference between dipole and quadrupole modes, we achieve efficient wavelength separation, enabling high absorption at the control wavelength without sacrificing signal transmission. This approach results in a 381% intensity modulation at λ_S= 473 nm under control light irradiation (λ_C= 405 nm) at 3.67 mW/μm². Our method significantly enhances modulation efficiency compared to conventional techniques, paving the way for ultrathin all-optical switches and active wavefront control devices.