Supplementary Material for Giant enhancement of the transverse magneto-optical Kerr effect in etchless bismuthsubstituted yttrium iron garnet empowered by quasi-bound states in the continuum

1.Physical mechanism behind the formation of bound states in the continuum 2.The effect of the grating geometry parameter δ on the Q factor 3.The feasible fabrication procedure of the proposed structure 4.Robustness of optical and magneto-optical responses against the grating sidewall tilted angle α 5. Comparative table of advantages for various structural designs