Fig. 2

Design principle and numerical analysis of the on-chip q-BIC-assisted metasurface for color routing and intensity tuning. a 3D schematic of on-chip diatomic pixels consisting of two parallel and two tilted nanoblocks, respectively, corresponding to the conversion from a BIC mode to a q-BIC mode. Here, θ is the tilting angle of the q-BIC meta-diatom. The local displacement between diatomic nanoblocks along the x-direction is designed to be P_x/2. b Schematic of on-chip q-BIC-assisted metasurface composed of pairs of tilted rectangular nanoblocks integrated onto the waveguide. c, d Simulated electric-field intensity (|E | ²) distributions in the xy-plane for the two cases of tilting angle θ = 0° and θ = 20° when the TE₀ mode incidents from the x-direction. The corresponding parameters are L = 130 nm, W = 65 nm, P_x = P_y = 400 nm, and H = 380 nm. e Electric-field intensity distributions (|E|²) in the yz-plane for the case of tilting angle θ = 0°, θ = 20°, and θ = 40°. f Simulated extraction spectrum contour of the on-chip BIC or q-BIC meta-diatomic array as the tilting angle varies from 0° to 20°. g Simulated extraction spectra of q-BIC meta-diatomic array with length L varying from 120 nm to 180 nm. The corresponding parameters are W = 60 nm, P_x = P_y = 400 nm, and H = 380 nm. h Line plot of extraction spectra of BIC or q-BIC meta-diatomic array for the case of tilting angle θ = 0°, θ = 10°, and θ = 20°, respectively, showing that the Q-factors vary from 23 to 18 as the angle θ increases from 10° to 20°. i Line plot of extraction spectra of q-BIC meta-diatomic array with the scaling factors S (as given by L = L₀ × S, W = W₀ × S, P = P₀ × S) varying from 0.85 to 1 while keeping θ fixed at 20°. The average Q-factor is ~17. The corresponding parameters are L₀ = 160 nm, W₀ = 60 nm, and P₀ = 400 nm when S = 1. j–l Simulated electric-field intensity (|E|²) profiles extracted from the waveguide at the wavelength of 572 nm, 608 nm, and 652 nm. The black arrows represent the propagation direction of the guided waves