Review

Towards omnidirectional, large scale, full polarization, and broadband practical invisibility cloaks: challenges and progress

¹ The Electromagnetics Academy at Zhejiang University, Zhejiang University, Hangzhou 310027, P.R. China
² Department of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, P.R. China
³ Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore
⁴ Centre for Disruptive Photonic Technologies, Nanyang Technological University, 637371 Singapore

^* e-mail: hansomchen@zju.edu.cn

Received: 25 June 2014
Accepted: 21 December 2014
Published online: 18 March 2015

Abstract

Invisibility cloaks have experienced a tremendous development in the past few years, but the current technologies to convert the cloaks into practical applications are still facing numerous bottlenecks. In this paper, we provide the review of the challenges and recent progress in the invisibility cloaks from a practical perspective. In particular, the following key challenges such as non-extreme parameters, homogeneity, omnidirectivity, full polarization, large scale and broad band are addressed. We analyze the physical mechanisms behind the challenges and consequently evaluate the merits and defects of the recent solutions. We anticipate some compromises on the ideal cloaks are required in order to achieve practical invisibility cloaks in the future.