Enhancing Goos-H\"anchen shift based on magnetic dipole quasi-bound states in the continuum in all-dielectric metasurfaces

TL;DR

This paper demonstrates giant Goos-H"anchen shift enhancement using magnetic dipole quasi-BIC resonances in all-dielectric metasurfaces, enabling advanced optical manipulation and ultrasensitive sensing.

Contribution

It introduces a novel approach to enhance GH shift via magnetic dipole quasi-BIC in silicon metasurfaces, with tunable Q-factor and potential for high-sensitivity sensors.

Findings

GH shift exceeds three orders of wavelength at reflection peak

GH shift inversely proportional to the square of asymmetry parameter

Maximum sensor sensitivity reaches 1.5×10^7 μm/RIU

Abstract

Metasurface-mediated bound states in the continuum (BIC) provides a versatile platform for light manipulation at subwavelength dimension with diverging radiative quality factor and extreme optical localization. In this work, we employ magnetic dipole quasi-BIC resonance in asymmetric silicon nanobar metasurfaces to realize giant Goos-H\"anchen (GH) shift enhancement by more than three orders of wavelength. In sharp contrast to GH shift based on the Brewster dip or transmission-type resonance, the maximum GH shift here is located at the reflection peak with unity reflectance, which can be conveniently detected in the experiment. By adjusting the asymmetric parameter of metasurfaces, the $Q$-factor and GH shift can be modulated accordingly. More interestingly, it is found that GH shift exhibits an inverse quadratic dependence on the asymmetric parameter. Furthermore, we design an ultrasensitive environmental refractive index sensor based on the quasi-BIC enhanced GH shift, with a maximum sensitivity of 1.5$\times$10$^{7}$ $\mu$m/RIU. Our work not only reveals the essential role of BIC in engineering the basic optical phenomena, but also suggests the way for pushing the performance limits of optical communication devices, information storage, wavelength division de/multiplexers, and ultrasensitive sensors.