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Invisible cloak design with controlled constitutive parameters and arbitrary shaped boundaries through Helmholtz's
Zheng Chang1, Xiaoming Zhou, Jin Hu
1School of Aerospace Engineering, Beijing Institute of Technology, Beijing 100081, PR China.
Abstract:
In a recent paper, Chen et al. [Opt. Express 17, 3581 (2009)] develop an approach to design invisible cloaks with controllable constitutive parameters by adjusting the constant k in the Helmholtz's equation. In this comment, we discuss the limitation of the free parameter k in designing cloaks. It is found that the real constant k can be chosen only as limited values in order to avoid the singular material parameters.
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