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

Abstract

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.

Interface state-based bound states in continuum and below-continuum-resonance modes with high-Q factors in the rotational periodic system

“…[8][9][10] PhC is widely used as the material to realize BIC due to its unique restrictions and transmission characteristics. [11][12][13] BICs can be viewed as special resonances with infinite Q factors because different radiation channels interfere destructively with each other in the far-field, [11,14,15] which makes them highly desirable for applications such as PhC lasers, [16] sensors, [17][18][19] beam shift, [20][21][22][23] filters, [24,25] fibers based on BIC, [26] and optical switches [27] that require high-Q factors. Furthermore, BICs hold great potential for further research and development.…”