Enhancing the Goos-Hänchen shift based on quasi-bound states in the continuum through material asymmetric dielectric compound gratings

Quasi-bound state in the continuum (QBIC) resonance is gradually attracting attention and being applied in Goos-Hänchen (GH) shift enhancement due to its high quality (Q) factor and superior optical confinement. Currently, symmetry-protected QBIC resonance is often achieved by breaking the geometric symmetry, but few cases are achieved by breaking the material symmetry. This paper proposes a dielectric compound grating to achieve a high Q factor and high reflection symmetry-protected QBIC resonance based on material asymmetry. Theoretical calculations show that the symmetry-protected QBIC resonance achieved by material asymmetry can significantly increase the GH shift up to -980 times the resonance wavelength, and the maximum GH shift is located at the reflection peak with unity reflectance. This paper provides a theoretical basis for designing and fabricating high-performance GH shift tunable metasurfaces/dielectric gratings in the future.