Browsing by Author "Popa, BI"

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    A broadband low-reflection metamaterial absorber
    (Journal of Applied Physics, 2010-09-15) Gu, S; Barrett, JP; Hand, TH; Popa, BI; Cummer, SA
    Artificially engineered metamaterials have enabled the creation of electromagnetic materials with properties not found in nature. Recent work has demonstrated the feasibility of developing high performance, narrowband electromagnetic absorbers using such metamaterials. These metamaterials derive their absorption properties primarily through dielectric loss and impedance matching at resonance. This paper builds on that work by increasing the bandwidth through embedding resistors into the metamaterial structure in order to lower the Q factor and by using multiple elements with different resonances. This is done while maintaining an impedance-matched material at normal incidence. We thus present the design, simulation, and experimental verification of a broadband gigahertz region metamaterial absorber, with a maximum absorption of 99.9% at 2.4 GHz, and a full width at half maximum bandwidth of 700 MHz, all while maintaining low reflection inside and outside of resonance. © 2010 American Institute of Physics.
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    Design of layered transformation-optics devices of arbitrary shape
    (Physical Review A - Atomic, Molecular, and Optical Physics, 2010-09-30) Popa, BI; Cummer, SA
    Transformation-optics devices of arbitrary shapes usually result in material parameters inside the device that feature level sets of different shapes. Consequently, these devices cannot easily be implemented using a layered architecture and thus are, generally, more difficult to realize in practice. We present a method of designing two-dimensional transformation-optics devices of arbitrary shapes characterized by material parameters of same-level sets, thus suitable to be implemented through concentric layers, each layer being made of a single type of material or metamaterial. Remarkably, we show that transformations leading to such designs are obtained from solutions to the well-known eikonal equation. This approach allows fabrication techniques developed for cylindrical designs of circular cross section to be directly applied to devices of other shapes. © 2010 The American Physical Society.