arXiv subjects

Y. Hadad

Publications and source records attributed to Y. Hadad.

5 recordsLinked to original sources

arXiv2015

Planar One-way Guiding in Periodic Particle Arrays with Asymmetric Unit Cell and General Group-Symmetry Considerations

We develop a general theory for one-way optical guiding in magnetized periodic particle arrays. Necessary conditions for a non-even dispersion curves are derived and presented in the context of Frieze symmetry-groups. It is shown, for example, that one-way guiding can be supported in particle \emph{strips} consisting of geometrically isotropic particles arranged in transversely asymmetric arrays. Specific examples consist e.g.~two parallel isotropic particle chains with different periods. The previously studied one-way effect based on the two-type rotation principle is shown to be a special case. In the latter the exclusion of the appropriate Frieze-symmetries is achieved in a single linear chain by associating a geometric rotation to each particle, thus providing the narrowest possible one-way waveguides. It is also shown that nearly any randomly created period may result in uneven dispersion and one-way guiding.

cond-mat.str-el↗

arXiv2015

Space-time gradient metasurfaces

Metasurfaces characterized by a transverse gradient of local impedance have recently opened exciting directions for light manipulation at the nanoscale. Here we add a temporal gradient to the picture, showing that spatio-temporal variations over a surface may largely extend the degree of light manipulation in metasurfaces, and break several of their constraints associated to symmetries. As an example, we synthesize a non-reciprocal classical analogue to electromagnetic induced transparency, opening a narrow window of one-way transmission in an otherwise opaque surface. These properties pave the way to magnetic free, planarized non-reciprocal ultrathin surfaces for free-space isolation.

cond-mat.mes-hall↗

arXiv2011

One-way optical waveguides for perfectly matched non-reciprocal nano-antennas with dynamic beam tuning

An optical signal that propagates along a conventional waveguide is back reflected at waveguide terminations. If the waveguide permits only one-way propagation, this back reflection cannot take place; the optical signal undergoes a nearly 100% conversion to radiation modes. Hence, a terminated one-way waveguide may serve as a matched nano-antenna with a natural guiding and feeding mechanism. We examine the termination effect in a recently suggested nano-scale one-way plasmonic waveguide, and its properties as a matched nano antenna are shown. Since one-way structures are inherently non-reciprocal, our antenna possesses different transmitting and receiving patterns, and a dynamic beam-forming functionality. These unique properties offer new possibilities for dynamic directional selectivity that differ in transmit and receive operations. Finally, the new concept offers nano-antennas as yet another important field of application for non-reciprocal nano-photonics, accelerating research of both the former and the latter fields of activity.

physics.optics↗

arXiv2010

Effects of Radiation-Reaction in Relativistic Laser Acceleration

The goal of this paper is twofold: to explore the response of classical charges to electromagnetic force at the level of unity in natural units and to establish a criterion that determines physical parameters for which the related radiation-reaction effects are detectable. In pursuit of this goal, the Landau-Lifshitz equation is solved analytically for an arbitrary (transverse) electromagnetic pulse. A comparative study of the radiation emission of an electron in a linearly polarized pulse for the Landau-Lifshitz equation and for the Lorentz force equation reveals the radiation-reaction dominated regime, in which radiation-reaction effects overcome the influence of the external fields. The case of a relativistic electron that is slowed down by a counter propagating electromagnetic pulse is studied in detail. We further show that when the electron experiences acceleration of order unity, the dynamics of the Lorentz force equation, the Landau-Lifshitz equation and the Lorentz-Abraham-Dirac equation all result in different radiation emission that could be distinguished in experiment. Finally, our analytic and numerical results are compared with those appearing in the literature.

hep-ph↗

arXiv2010

Magnetized spiral chains of plasmonic ellipsoids for one-way optical waveguides

When a linear chain of plasmonic nano-particles is subject to longitudinal magnetic field, it exhibits optical Faraday rotation. If the magnetized nano-particles are plasmonic ellipsoids arranged as a spiral chain, the interplay between the Faraday rotation and the geometrical spiral rotation (structural chirality) can strongly enhance non-reciprocity. This interplay forms a waveguide that permits one way propagation only, within four disjoint frequency bands; two bands for each direction.

physics.optics↗