Invisibility Exposed: Physical Bounds on Passive Cloaking

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July 5, 2016

Prof. Andrea Alù’s and PhD candidate Francesco Monticone’s research paper titled ‘Invisibility Exposed: Physical Bounds on Passive Cloaking’ will be published in the Optical Society’s flagship journal Optica in the upcoming issue. Together, Prof. Alù and Monticone have established quantitative physical limitations on the performance of cloaking devices, a technology that allows objects to become invisible or undetectable for electromagnetic waves, such as radio waves, microwaves, infrared and visible light.

Optica is an open-access, online-only journal that focuses on rapid dissemination of high-impact peer-reviewed research across the entire spectrum of optics and photonics. The Optical Society (OSA) publishes the journal monthly. Optica provides a forum for pioneering research to be swiftly accessed by the international community. The journal publishes articles, which are of significant interest to the optics and broader scientific community.

Prof. Alù and Monticone created a quantitative framework establishing the boundaries on the bandwidth of passive cloaking devices based on the size and composition of the object to be concealed. It can calculate the ultimate expectable performance of passive invisibility devices, in terms of bandwidth and achievable scattering reduction, before attempting a specific design of the cloaking device.

In addition to providing a practical guide for research on passive cloaking devices, the proposed framework can help dispel some of the myths that have developed around cloaking and its potential to make large objects invisible.

Prof. Alù, Associate Professor at Texas ECE, is also affiliated with the Wireless Networking and Communications Group, an interdisciplinary center for research and education based in UT Austin with an emphasis on industrial relevance, and with the Applied Research Laboratories at UT Austin. His research interests span over a broad range of technical areas, including applied electromagnetics, nano-optics and nanophotonics, microwave, THz, infrared, optical and acoustic metamaterials and metasurfaces, plasmonics, nonlinearities and nonreciprocity, cloaking and scattering, acoustics, optical nanocircuits and nanoantennas.

Monticone works closely with Prof. Alù in the Metamaterials and Plasmonics Research group. His research interests include the areas of applied electromagnetics, metamaterials, plasmonics, and nanophotonics, with applications ranging from microwaves to optical frequencies, and with high scientific and industrial impact.

Prof. Alù’s lab is working on the design of active cloaking devices, which use metamaterials and an external energy source to achieve broader transparency bandwidths. Although a relatively new research area, active cloaks have proven they can go beyond the bounds of passive cloaks. “Even with active cloaks, Einstein’s relativity and causality fundamentally limit the performance of invisibility cloaks,” Prof. Alù said. “Yet, with new concepts and designs, such as active and non-linear metamaterials, it is possible to move forward in the quest for invisibility.”

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