Browsing by Author "Valagiannopoulos, Constantinos A."
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- Breaking the black-body limit with resonant surfaces
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2017) Valagiannopoulos, Constantinos A.; Simovski, Constantin R.; Tretyakov, Sergei A.The speed with which electromagnetic energy can be wirelessly transferred from a source to the user is a crucial indicator for the performance of a large number of electronic and photonic devices. We expect that energy transfer can be enhanced using special materials. In this paper, we determine the constituent parameters of a medium which can support theoretically infinite energy concentration close to its boundary; such a material combines properties of Perfectly Matched Layers (PML) and Double-Negative (DNG) media. It realizes conjugate matching with free space for every possible mode including, most importantly, all evanescent modes; we call this medium Conjugate Matched Layer (CML). Sources located outside such layer deliver power to the conjugate-matched body exceptionally effectively, impressively overcoming the black-body absorption limit which takes into account only propagating waves. We also expand this near-field concept related to the infinitely fast absorption of energy along the air-medium interface to enhance the far-field radiation. This becomes possible with the use of small particles randomly placed along the boundary; the induced currents due to the extremely high-amplitude resonating fields can play the role of emission ‘‘vessels’’, by sending part of the theoretically unlimited near-field energy far away from the CML structure. - Hyperbolic-metamaterial antennas for broadband enhancement of dipole emission to free space
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2014) Valagiannopoulos, Constantinos A.; Mirmoosa, Mohammad S.; Nefedov, Igor S.; Tretyakov, Sergei A.; Simovski, Constantin R. - Theoretical concepts of unlimited-power reflectors, absorbers, and emitters with conjugately matched layers
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2016-09-12) Valagiannopoulos, Constantinos A.; Tretiakov, SergeiRecently, it was shown that by using special artificial materials it is possible to ensure that all electromagnetic modes of free space are conjugately matched to the modes of a material body and, thus, all modes deliver power to the body in the most effective way. Such a fascinating feature is acquired because the conjugate matching does not concern only the propagating modes but, most importantly, is applied to all evanescent modes; in this way, all the possible ways of transferring the electromagnetic energy to the material body can be optimally exploited. However, coupling to higher-order (mostly evanescent) modes is weak and totally disappears in the limit of an infinite planar boundary. Here, we show that by properly perturbing the surface of the receiving or emitting body with, for example, randomly distributed small particles, we can open up channels for super-radiation into the far zone. The currents induced in the small particles act as secondary sources (radiation "vessels") which send the energy to travel far away from the surface and, reciprocally, receive power from far-located sources. For a particular example, we theoretically predict about 20-fold power transfer enhancement between the conjugately matched power-receiving body (as compared with the ideal black body) and far-zone sources. Reciprocally, the proposed structure radiates about 20 times more power into the far zone as compared with the same source over a perfect reflector.