Abstract
Toward the goal of achieving broadband and omnidirectional invisibility, we propose a method for practical invisibility cloaking. We call this “digital cloaking,” where space, angle, spectrum, and phase are discretized. Experimentally, we demonstrate a two-dimensional (2D) planar, ray optics, digital cloak by using lenticular lenses, similar to “integral imaging” for three-dimensional (3D) displays. Theoretically, this can be extended to a good approximation of an “ideal” 3D cloak. With continuing improvements in commercial digital technology, the resolution limitations of a digital cloak can be minimized.
Highlights
An “ideal” invisibility cloak can be considered to be broadband, omnidirectional, 3D, macroscopic, and operational in the visible spectrum, and have phase matching for the full field of light [1]
This corresponds to the range of transverse spatial positions of the objects that are captured for each detector pixel of the input camera
As shown in Visualization 3 and Supplement 1, our demonstrated depth of field was over 60 cm, such that all the objects we demonstrated for the cloak (Figs. 2 and 3) were at least in good focus when collected for input
Summary
An “ideal” invisibility cloak can be considered to be broadband, omnidirectional, 3D, macroscopic, and operational in the visible spectrum, and have phase matching for the full field of light [1]. To demonstrate cloaking, researchers have relaxed these or other ideal characteristics Some of these efforts include broadband “carpet cloaks” for visible light on reflective surfaces [7], unidirectional phasematching cloaks [8], macroscopic ray optics cloaking [9,10], a cylindrical cloak for light through a diffusive medium [11], or a cloak that achieves all in the small-angle regime [6]. Other active cloaks, which compensate for absorption and increase bandwidth, include using active metamaterial surfaces for dominant scattering cancellation or using electronic circuits for acoustic cloaks [5]. These rely on custom-engineered material, whereas our digital cloaks can use commercially available technology that is improving independently of any cloaking efforts. We believe this will be an advantage for scaling and implementation
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