Fig. 3: High-Q GMRs.

a Schematic drawing of a meta-waveguide system made of an ultrathin SiO₂ grating on top of 220 nm-Si on SiO₂ substrate. b The Q-factor of GMR mode TE₃₁ vs thickness of top perturbation layer. Solid and dashed lines refer to the numerically calculated Q-factor and fitting Q-factor. The structure parameters are p = 548 nm and w = 200 nm. c The Q-factor of GMR mode TE₃₁ vs grating’s width. Solid and dashed lines show the numerically calculated Q-factor and fitting Q-factor. The structure parameters are p = 548 nm and t = 40 nm. d Schematic drawing of a meta-waveguide system made of an ultrathin SiO₂ compound grating on top of 220 nm-Si on SiO₂ substrate. e The Q-factor of QBIC TE₂₁ (solid red) and GMR TE₃₁ (solid blue) vs thickness of top perturbation layer. Dashed lines are fitting Q-factor. The structure parameters are p = 548 nm, w = 110 nm, d = 90 nm, g = 120 nm, xc = 10 nm. f The Q-factor of BIC TE₂₁ (solid red) and GMR TE₃₁ (solid blue) vs gap center xc. The structure parameters are p = 548 nm, w + d = 200 nm, g = 120 nm. Dashed lines are fitting Q-factors. g Schematic drawing of a meta-waveguide system made of an ultrathin SiO₂ metasurface on top of 220 nm-Si on SiO₂ substrate. h The Q-factor of GMR mode TE₃₁₁ vs the thickness of top perturbation layer. Solid and dashed lines show the numerically calculated Q-factor and fitting Q-factor. The structure parameters are p = 548 nm, w = 200 nm. i The Q-factor of BIC TE₂₁₁ (solid red) and GMR TE₃₁₁ (solid blue) vs top layer thickness. Dashed lines are fitting Q-factor. The structure parameters are p = 548 nm, w + d = 200 nm, g = 120 nm.