Macroscopic Invisibility Cloak for Visible Light

TLDR

Invisibility cloaks have attracted wide interest, yet the major challenge remains cloaking a macroscopic object across the entire visible spectrum. The study aims to experimentally solve this problem by applying transformation optics to a conventional optical lens design. The method integrates transformation optics into a conventional lens fabrication using low‑cost materials and simple manufacturing techniques. A transparent cloak composed of two calcite pieces was fabricated, successfully concealing a 2 mm‑high object (over 3500 wavelengths) in a transparent liquid across the red, green, and blue spectrum.

Abstract

Invisibility cloaks, a subject that usually occurs in science fiction and myths, have attracted wide interest recently because of their possible realization. The biggest challenge to true invisibility is known to be the cloaking of a macroscopic object in the broad range of wavelengths visible to the human eye. Here we experimentally solve this problem by incorporating the principle of transformation optics into a conventional optical lens fabrication with low-cost materials and simple manufacturing techniques. A transparent cloak made of two pieces of calcite is created. This cloak is able to conceal a macroscopic object with a maximum height of 2 mm, larger than 3500 free-space-wavelength, inside a transparent liquid environment. Its working bandwidth encompassing red, green, and blue light is also demonstrated.