Directional beaming of light from a subwavelength metal slit with phase-gradient metasurfaces

Hua Zhu,Xun Li,Lin Chen,Xiang Yin

doi:10.1038/s41598-017-09726-9

Abstract

In this article, we demonstrate directional beaming of light from a metal nanoslit surrounded with phase-gradient metasurfaces on both sides. Distinct from the grating-based beaming structures, here the momentum mismatch between the surface wave and radiation wave is overcome by the phase-gradient metasurfaces. The deviation angle of the directional beam can be flexibly adjusted by appropriately arranging the phase-gradient of metasurfaces on each side of the nanoslit. The metasurface-based beaming structures also present the ability to operate with high diffraction efficiency and small divergence angle, implying various potential applications in nanophotonics.

Highlights

Controlling the flow and propagation of light has always been the main theme in the field of optics
It is highly desirable for many applications to redirect light in a desired direction as a collimated beam, which has the great potential to promote the development of optical sensors, high-density optical data storage, divergence-controlled lasers, and so forth
Metasurfaces have enabled a variety of unique phenomena and applications that are unattainable with conventional materials, including anomalous reflection/refraction[11,12,13,14,15,16,17], planar optical lenses[15, 18,19,20], polarization converters[21,22,23], vortex plates[24, 25], ultrathin high-resolution holograms[26, 27], and enhancement of nonlinear optical responses[28, 29]

Summary

Introduction

Controlling the flow and propagation of light has always been the main theme in the field of optics. We demonstrate that well-designed phase-gradient metasurfaces surrounding a metal nanoslit can be used to realize directional beaming of light. Distinct from the grating-based beaming structures, here the momentum mismatch between the SW and radiation wave is compensated by the phase-gradient metasurfaces.

Results

Conclusion