Goos–Hanchen shift in a metasurface of core–shell nanoparticles

Abstract

Metasurfaces are periodic subwavelength structures that have found applications in functional devices such as image sensors, cameras, and microscopes. They are able to modulate the amplitude, phase, and polarization of incident light. Reflected light from a surface exhibits a deviation from the rules governed by geometric optics and displaces in directions parallel and perpendicular to plane of incidence. The sharp phase changes at reflection from a metasurface would be useful in enhancing the longitudinal reflection shifts, known as Goos–Hanchen​ (GH) shift. In this article, using generalized sheet transition conditions, we study GH shift in a metasurface composed of spherical metal-oxide core with plasmonic shell nanoparticles in a square array. A detailed analysis reveals that reflection shifts of this type of nanostructures can be tuned delicately by varying the size, core-to-shell ratio and periodicity of particles as well as light wavelength and angle of radiation. Large reflection shifts are achievable in both visible and ultraviolet ranges due to plasmonic resonance of metallic shell. Such sensitivity could be useful in very sensitive beam deflection measurements like in AFM or in reflective UV sensors.