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Electromagnetic Metamaterials
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Electromagnetic Metamaterials and their
Approximations:
Practical and Theoretical Aspects
CSIC Building (#406),
Seminar Room 4122.
Directions: home.cscamm.umd.edu/directions
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A Dielectric Invisibility Carpet
Dr. Jensen Li
University of California, Berkeley
NSF Nanoscale Science and Engineering Center (NSEC)
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Abstract:
Transformation optics, driven by coordinate transformation, essentially induces a profile of permittivity and permeability together with anisotropy in the transformed media of a cloak. This is fulfilled by metamaterials which, upon careful designs, can attain a large range of the permittivity and the permeability tensors. As a result, an electromagnetic cloak in the microwave regime becomes feasible. Apart from cloaking, other kinds of devices like the field concentrator and the field rotator can be designed by the same guiding principle. However, when we work at frequencies near the visible regime, scaling down conventional metamaterials causes severe absorption because of its resonating nature and also fabrications become more difficult.
In this talk, we discuss the possibility in avoiding the use of the resonating structures in metamaterials. We explore the flexibility of the coordinate transformations. Among the many possible coordinate transformations, the quasi-conformal mapping is a natural extension from the conformal mapping. It remains orthogonal such that the permittivity and the permeability tensors can be easily realized because the principle axes of the tensors align with the coordinate lines. We develop a numerical procedure in generating the mapping in designing a cloak to turn an object into a flat conducting plane, i.e. an invisibility carpet. The anisotropy within the cloak remains a constant that can be made very small. Although the cloaking is not perfect, it can lead us to easier realizations by using dielectrics.
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