High-Q filtering and dynamic modulation in all-dielectric metasurfaces induced by quasi-BIC

The all-dielectric metasurfaces can significantly reduce the volume of optical components while having low loss and high performance, which has become a research hotspot in recent years. However, due to the complexity of metasurface geometric design, it is challenging to realize dynamic modulation on all-dielectric metasurface optical elements. Here, we propose a high quality factor (high-Q) pass-band filter designed by introducing the quasi-bound states in the continuum (quasi-BIC) into the silicon array phase-gradient metasurfaces. Our simulations show that due to the quasi-BIC effect only a high-Q resonance with the linewidth less than 1 nm and the corresponding Q value of ∼37000 could transmit along the zeroth order direction, which could be used for ultra-narrow linewidth filtering. Furthermore, our simulations present that the near-fields of the waveguide modes supported by the silicon arrays are partially distributed inside the indium tin oxide (ITO) substrate, which makes it possible to dynamically tune the central wavelength of our proposed filter by varying the ITO refractive index.