Study on transformation-based invisibility cloaks

The combination of the development of modern metamaterials, which are artificial materials whose constitutive parameters can be engineered to achieve special functions, and the coordinate transformation theory, has offered an unprecedented opportunity for realizing invisibility cloaking. Coordinate transformation theory predicts that by squeezing the space to form a "hole" in it, any object inside the "hole" becomes completely invisible from electromagnetic waves. A metamaterial shell can thus be designed to mimic this space squeezing and function as an invisibility cloak whose user cannot be seen by others. In this thesis, a systematic electromagnetic study of transformation-based invisibility cloaks is provided based on the macroscopic Maxwell equations. Analytic scattering models are formulated for studying ideal and non-ideal invisibility cloaks. The physics behind perfect invisibility that the coordinate transformation theory did not show is explored by analytically calculating the spatial distribution of electromagnetic fields. Firstly, it is shown that an external electromagnetic wave illuminating a cylindrical cloak will induce electric and magnetic surface currents along the 0 direction at the inner boundary of this cloak. These surface currents have no counterparts in the transformation theory because they do not exist before transformation. Secondly, the reciprocity of a spherical cloak is demonstrated by showing that radiation from an active device in the concealed region is confined in the concealed region. The mechanism is that the outgoing radiation will induce surface voltages at the inner boundary of the cloak that reflect all waves back.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2009

Author dc:creator

• Zhang, Baile

Advisor dc:contributor.advisor

• David Staelin and Bae-Ian Wu.

• Electrical Engineering and Computer Science.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/53309

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/53309