Abstract
Invisible cloaking is one of the major outcomes of the metamaterial research, but the practical potential, in particular for high frequencies (for example, microwave to visible light), is fatally challenged by the complex material properties they usually demand. On the other hand, it will be advantageous and also technologically instrumental to design cloaking devices for applications at low frequencies where electromagnetic components are favourably uncoupled. In this work, we vastly develop the bilayer approach to create a three-dimensional magnetic cloak able to work in both static and dynamic fields. Under the quasi-static approximation, we demonstrate a perfect magnetic cloaking device with a large frequency band from 0 to 250 kHz. The practical potential of our device is experimentally verified by using a commercial metal detector, which may lead us to having a real cloaking application where the dynamic magnetic field can be manipulated in desired ways.
Highlights
Invisible cloaking is one of the major outcomes of the metamaterial research, but the practical potential, in particular for high frequencies, is fatally challenged by the complex material properties they usually demand
These experimental progresses enabled by the bilayer approach may bring us more confidence to pursue a practical cloaking device for applications at low frequencies where the quasi-static approximation is valid[39]
The SC component we use is carefully manufactured from single-crystal yttrium barium copper oxide (YBCO) cylinders, whose bulk and single-crystal features could exclude many possible negative material issues related to inductive loss
Summary
Invisible cloaking is one of the major outcomes of the metamaterial research, but the practical potential, in particular for high frequencies (for example, microwave to visible light), is fatally challenged by the complex material properties they usually demand. There is a general question of whether the SC component can still be as effective as a zero-permeability entity in time-varying fields where inhomogeneous vectorial Helmholtz equations have to apply Regarding these critical issues, in this work we vastly develop the bilayer approach to pursue a magnetic cloak operational in a 3D quasi-static field by optimizing material properties. The SC component we use is carefully manufactured from single-crystal yttrium barium copper oxide (YBCO) cylinders, whose bulk and single-crystal features could exclude many possible negative material issues related to inductive loss With such a bilayer structure, here we experimentally show a perfect 3D magnetic cloak working from d.c. to a maximum measurement frequency of 250 kHz, which covers the operation bands of most EMI appliances. The application potential to hide objects in a real field is examined by using a commercial metal detector
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