Homogeneous optical cloak constructed with uniform layered structures

TL;DR

This paper demonstrates a broadband, large-object invisibility cloak using a uniform silicon grating structure, simplifying design and expanding potential applications across frequency ranges.

Contribution

It introduces a homogenous invisibility cloak with a uniform layered structure, eliminating the need for spatially varying refractive indices.

Findings

Successfully realized a broadband invisibility at near-infrared frequencies.

Enables large obstacle cloaking with a high obstacle-to-cloak size ratio.

Uses a simple, uniform silicon grating structure for cloak design.

Abstract

The prospect of rendering objects invisible has intrigued researchers for centuries. Transformation optics based invisibility cloak design is now bringing this goal from science fictions to reality and has already been demonstrated experimentally in microwave and optical frequencies. However, the majority of the invisibility cloaks reported so far have a spatially varying refractive index which requires complicated design processes. Besides, the size of the hidden object is usually small relative to that of the cloak device. Here we report the experimental realization of a homogenous invisibility cloak with a uniform silicon grating structure. The design strategy eliminates the need for spatial variation of the material index, and in terms of size it allows for a very large obstacle/cloak ratio. A broadband invisibility behavior has been verified at near-infrared frequencies, opening up new oppotunities for using uniform layered medium to realize invisibility at any frequency ranges, where high-quality dielectrics are available.