High-Performance Electrical and Electro-Thermal Switch by Quasi-Bound States in the Continuum

This work demonstrates a graphene-based metasurface with the capability to support two high quality factor (
Q
-factor) quasi-bound states in the continuum via introducing geometry perturbation in the ultra-thin silicon resonators film. In contrast to the lossless dielectric metasurface, the spectral
Q
-factor are observed to present remarkably distinct relationships of the asymmetry degree for the graphene based lossy metasurface. It is observed that the material loss of graphene and the structural symmetry-breaking in the silicon resonator make a trade-off contribution for the resonant behaviors. Moreover, electrical manipulation is realized by slightly adjusting the graphene's Fermi level, with the optimal switch contrast, modulation depth, and extinction ratio reaching 57900%, 99.8%, and −27.6 dB, respectively. Furthermore, quantitatively electro-thermal modulation and switch are simultaneously achieved via applying voltage to excite the thermal generation in the graphene layer, showing near-unity intensity change under a single-digit level of temperature elevation (∼2 K). The findings suggest potential applications in optical switches, modulators, and temperature sensors.