arXiv subjects

Mohamed A. Salem

Publications and source records attributed to Mohamed A. Salem.

4 recordsLinked to original sources

arXiv2018

Microwave Vortex Beam Launcher Design

A novel design for a vectorial vortex beam launcher in the microwave regime is devised. The beam is formed by launching a single guided transverse electric (TE) mode of a metallic circular waveguide into free-space. Excitation is achieved by the mean of an inserted coaxial loop antenna. Modal expansion coefficients are computed, and the resulting electric and magnetic fields are determined. The effect of the antenna location inside the waveguide on its effective input impedance is modelled using transmission-line relations and location for optimal matching is established. The analytical results are confirmed using multi-level fast multipole method full-wave simulations.

physics.app-ph↗

arXiv2015

Space-Time Cross-Mapping and Application to Wave Scattering

Causality creates an asymmetry between space and time, even though the wave equation treats them on equal footing. In this work, we leverage this asymmetry to construct a cross-mapping between space and time. This cross-mapping is applied to simplify scattering in space-varying media, by eliminating the infinite reflections between interfaces. The method is shown to transform the implicit transfer matrix method into an explicit method for the analysis of electromagnetic field scattering by a stratified medium.

physics.optics↗

arXiv2015

Electromagnetic Fields Radiated by a Circular Loop with Arbitrary Current

We present a rigorous approach to compute the electromagnetic fields radiated by a thin circular loop with arbitrary current. We employ a polar transmission representation along with a Kontorovich-Lebedev transform to derive integral representations of the field in the interior and exterior regions of a sphere circumscribing the loop. The convergence of the obtained expressions is discussed and comparisons with full-wave simulation and other methods are shown.

physics.class-ph↗

arXiv2014

Manipulating light at distance by a metasurface using momentum transformation

A momentum conservation approach is introduced to manipulate light at distance using metasurfaces. Given a specified field existing on one side of the metasurface and specified desired field transmitted from the opposite side, a general momentum boundary condition is established, which determines the amplitude, phase and polarization transformation to be induced by the metasurface. This approach, named momentum transformation, enables a systematic way to synthesize metasurfaces with complete control over the reflected and transmitted fields. Several synthesis illustrative examples are provided: a vortex hypergeometric-Gaussian beam and a "delayed-start" accelerated beam for Fresnel region manipulation, and a pencil beam radiator and a holographic repeater for Frauenhofer region manipulation.

physics.optics↗