Refractive index sensing and switching of leaky states in a metasurface.

We theoretically propose leaky states in an electro-optic (EO)-based all-dielectric metasurface. The EO substrate tunes leaky modes to the desired wave band with changes in applied voltage (Vapp). For refractive index (RI) sensing, the highest figure-of-merit (FoM) in this work is 9166, quality factor (Q-factor) is 1.7450e4, sensitivity is 407 nm/RIU (in RI range of 1.00-1.03), minimum detectable RI is 1.0542e-4, and relative sensitivity is 9.94e-4V-1. The structure sustains the figure and line shape of leaky modes, high Q-factor, and FoM at different Vapp and EO-coefficients. Our FoM and Q-factor are high, and the minimum detectable RI is smaller than previously reported. The giant Q-factor is promising for optical filters, modulation, and slow-light device applications.