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Please use this identifier to cite or link to this item: http://hdl.handle.net/1807/17776

Title: Free-Space Metamaterial Superlenses Using Transmission-line Techniques
Authors: Iyer, Ashwin K.
Advisor: Eleftheriades, George V.
Department: Electrical and Computer Engineering
Keywords: Electromagnetic
Metamaterial
Microwave
Lens
Issue Date: 24-Sep-2009
Abstract: Free-space imaging with a resolution beyond that dictated by the classical diffraction limit may be achieved with a `Veselago-Pendry' superlens made from a metamaterial possessing a number of specific properties, including a negative refractive index (NRI). Although a planar NRI transmission-line (NRI-TL) metamaterial based on the periodic lumped loading of a host TL network has successfully verified the phenomenon of superlensing in a 2D microstrip environment, a true Veselago-Pendry superlens capable of interacting with and manipulating fields in free space remained elusive, largely due to the difficulty of meeting its stringent design constraints and also to the problem of realizing a full 3D isotropic, polarization-independent structure. This work presents the first experimental verification of free-space Veselago-Pendry superlensing using a new class of volumetric metamaterials based on 2D NRI-TL layers that, although polarization-specific, may be easily constructed using available lithographic techniques to interact with free-space sources. An equivalent-circuit model is developed to enable accurate design of the metamaterial's dispersion and transmission characteristics, including those associated with Veselago-Pendry superlensing, and is validated using full-wave simulations. First, a volumetric NRI-TL metamaterial employing fully printed loading elements is fabricated to verify the salient properties of a free-space metamaterial-slab lens. This lens demonstrates diffraction-limited focusing at X-band and, thus, affirms theoretical results that suggest that electrically thick and lossy metamaterials are unable to perform superlensing. Thereafter, a volumetric NRI-TL metamaterial based on discrete lumped elements is designed to meet the conditions of the Veselago-Pendry superlens at 2.40GHz, and experimentally demonstrates a resolution ability over three times better than that afforded by the classical diffraction limit. A microwave superlens designed in this fashion can be particularly useful for illumination and discrimination of closely spaced buried objects over practical distances by way of back-scattering, for example, in tumour or landmine detection, or for targeted irradiation over electrically small regions in tomography or hyperthermia applications. Possible optical implementations of the volumetric topology are also suggested, and finally, a fully isotropic, polarization-independent 3D metamaterial structure related to the volumetric NRI-TL structure is proposed.
URI: http://hdl.handle.net/1807/17776
Appears in Collections:Doctoral
The Edward S. Rogers Sr. Department of Electrical & Computer Engineering - Doctoral theses

Files in This Item:

File Description SizeFormat
Iyer_Ashwin_K_200906_PhD_thesis.pdfMain Thesis File10.24 MBAdobe PDF
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Iyer_Ashwin_K_200906_PhD_movieS2.aviRaw measured field phase over the measured region of Fig. 6.11(a) when the NRI-TL lens is illuminated by a single loop antenna, as they vary from 10GHz to 12GHz.7.57 MBMicrosoft AVIView/Open
Iyer_Ashwin_K_200906_PhD_movieS3.aviRaw measured field magnitudes over the measured region of Fig. 7.7(b) when the NRI-TL superlens is illuminated by a single loop antenna, as they vary from 2.0GHz to 2.6GHz. The magnitudes are normalized to the maximum value at the focal plane (dashed line) at 2.4GHz, and the black contour indicates the half-power level below this value.6.22 MBMicrosoft AVIView/Open
Iyer_Ashwin_K_200906_PhD_movieS4.aviRaw measured field phase over the measured region of Fig. 7.7(b) when the NRI-TL superlens is illuminated by a single loop antenna, as they vary from 2.0GHz to 2.6GHz. The dashed line indicates the expected focal plane.7.51 MBMicrosoft AVIView/Open
Iyer_Ashwin_K_200906_PhD_movieS5.aviRaw measured field magnitudes over the measured region of Fig. 7.7(b) when the NRI-TL superlens is illuminated by two loop antennas separated by lambda_0/3, as they vary from 2.0GHz to 2.6GHz. The magnitudes are normalized to the maximum value at the focal plane (dashed line) at 2.4GHz, and the black contour indicates the half-power level below this value.7.45 MBMicrosoft AVIView/Open
Iyer_Ashwin_K_200906_PhD_movieS1.aviRaw measured field magnitudes over the measured region of Fig. 6.11(a) when the NRI-TL lens is illuminated by a single loop antenna, as they vary from 10GHz to 12GHz. The magnitudes are normalized to the maximum value over the region at 11.355GHz, and the black contour indicates the half-power level below this value.6.44 MBMicrosoft AVIView/Open
Iyer_Ashwin_K_200906_PhD_movieS6.aviRaw measured field phase over the measured region of Fig. 7.7(b) when the NRI-TL superlens is illuminated by two loop antennas separated by lambda_0/3, as they vary from 2.0GHz to 2.6GHz. The dashed line indicates the expected focal plane.7.3 MBMicrosoft AVIView/Open

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