Abstract-Tunable beam steering enabled by graphene metamaterials

B. Orazbayev, M. Beruete, and I. Khromova
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-8-8848

We demonstrate tunable mid-infrared (MIR) beam steering devices based on multilayer graphene-dielectric metamaterials. The effective refractive index of such metamaterials can be manipulated by changing the chemical potential of each graphene layer. This can arbitrarily tailor the spatial distribution of the phase of the transmitted beam, providing mechanisms for active beam steering. Three different beam steerer (BS) designs are discussed: a graded-index (GRIN) graphene-based metamaterial block, an array of metallic waveguides filled with graphene-dielectric metamaterial and an array of planar waveguides created in a graphene-dielectric metamaterial block with a specific spatial profile of graphene sheets doping. The performances of the BSs are numerically analyzed, showing the tunability of the proposed designs for a wide range of output angles (up to approximately 70°). The proposed graphene-based tunable beam steering can be used in tunable transmitter/receiver modules for infrared imaging and sensing.

© 2016 Optical Society of America

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Abstract-Terahertz carpet cloak based on a ring resonator metasurface

B. Orazbayev, N. Mohammadi Estakhri, M. Beruete, and A. Alù

Phys. Rev. B 91, 195444 – Published 29 May 2015

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.91.195444

In this work we present the concept and design of an ultrathin (λ/22) terahertz (THz) unidirectional carpet cloak based on the local phase compensation approach enabled by gradient metasurfaces. A triangular surface bump with center height of 4.1 mm (1.1λ) and tilt angle of 20° is covered with a metasurface composed of an array of suitably designed closed ring resonators with a transverse gradient of surface impedance. The ring resonators provide a wide range of control for the reflection phase with small absorption losses, enabling efficient phase manipulation along the edge of the bump. Our numerical results demonstrate a good performance of the designed cloak in both near field and far field, and the cloaked object mimics a flat ground plane within a broad range of incidence angles, over 35° angular spectrum centered at 45°. The presented cloak design can be applied in radar and antenna systems as a thin, lightweight, and easy to fabricate solution for radio and THz frequencies.

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Abstract-Exploiting the dispersion of the double-negative-index fishnet metamaterial to create a broadband low-profile metallic lens

Exploiting the dispersion of the double-negative-index fishnet metamaterial to create a broadband low-profile metallic lens B. Orazbayev, V. Pacheco-Peña, M. Beruete, and M. Navarro-Cía  »View Author Affiliations

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-23-7-8555

Optics Express, Vol. 23, Issue 7, pp. 8555-8564 (2015)
http://dx.doi.org/10.1364/OE.23.008555

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Metamaterial lenses with close values of permittivity and permeability usually display low reflection losses at the expense of narrow single frequency operation. Here, a broadband low-profile lens is designed by exploiting the dispersion of a fishnet metamaterial together with the zoning technique. The lens operates in a broadband regime from 54 GHz to 58 GHz, representing a fractional bandwidth ~7%, and outperforms Silicon lenses between 54 and 55.5 GHz. This broadband operation is demonstrated by a systematic analysis comprising Huygens-Fresnel analytical method, full-wave numerical simulations and experimental measurements at millimeter waves. For demonstrative purposes, a detailed study of the lens operation at two frequencies is done for the most important lens parameters (focal length, depth of focus, resolution, radiation diagram). Experimental results demonstrate diffraction-limited ~0.5λ transverse resolution, in agreement with analytical and numerical calculations. In a lens antenna configuration, a directivity as high as 16.6 dBi is achieved. The different focal lengths implemented into a single lens could be potentially used for realizing the front end of a non-mechanical zoom millimeter-wave imaging system.

© 2015 Optical Society of America