Invisibility devices, or cloaks, represent the quintessential example of how metamaterials can control and engineer wave propagation in unconventional ways. In this context, I have established – for the first time – fundamental limitations on the possibility of making an object invisible with an arbitrary passive cloak [1,2]. These physical bounds, derived from general passivity and causality considerations, represent a fundamental tool to quantitatively estimate the ultimate performance of passive cloaks, and assess their applicability and potential for practical applications. My findings also suggest new directions to approach and exceed these bounds, for example by using suitably designed multilayered cloaks, or by employing superconducting or active media, opening a new phase in the quest for invisibility.
Related Publications:
[1] F. Monticone, and A. Alù, “Invisibility Exposed: Physical Bounds on Passive Cloaking,” under review.
[2] F. Monticone, and A. Alù, “Do Cloaked Objects Really Scatter Less?,” Physical Review X, Special Issue on Metamaterials, Vol. 3, No. 4, 041005 (10 pages), October 21, 2013 (invited paper). (web) [Press coverage by BBC, NBC News, Physics World, Bio News Texas, Live Science, Gizmag, Mashable, The Horn, The Alcalde, National Journal, Time Magazine, among others].
[3] R. Fleury*, F. Monticone*, and A. Alù, “Invisibility and Cloaking: Origins, Present, and Future Perspectives,” Physical Review Applied, Vol. 4, No. 3, 037001 (20 pages), September 1, 2015, (invited review paper). (web)
[4] F. Monticone, and A. Alù, “Physical Bounds on Electromagnetic Invisibility and the Potential of Superconducting Cloaks,” Photonics and Nanostructures – Fundamentals and Applications, Special Issue for Metamaterials 2013, Vol. 12, No. 4, 330–339, August 2014 (invited paper). (web)
[5] P. Y. Chen, F. Monticone, and A. Alù, “Suppressing the Electromagnetic Scattering with an Helical Mantle Cloak,”IEEE Antennas and Wireless Propagation Letters, Special Cluster on Metamaterials, Vol. 10, pp. 1598-1601, December 9, 2011 (invited paper). (web)