B. Orazbayev

Ultra-compact planoconcave zoned metallic lens based on the fishnet metamaterial

A 1.5λ0-thick planoconcave zoned lens based on the fishnet metamaterial is demonstrated experimentally at millimeter wavelengths. The zoning technique applied allows a volume reduction of 60% compared to a full fishnet metamaterial lens without any deterioration in performance. The structure is designed to exhibit an effective refractive index n = −0.25 at f = 56.7 GHz (λ0 = 5.29 mm) with a focal length FL = 47.62 mm = 9λ0. The experimental enhancement achieved is 11.1 dB, which is in good agreement with simulation and also with previous full fishnet metamaterial lenses and opens the door for integrated solutions.

Zoned near-zero refractive index fishnet lens antenna: Steering millimeter waves

A zoned fishnet metamaterial lens is designed, fabricated, and experimentally demonstrated at millimeter wavelengths to work as a negative near-zero refractive index lens suitable for compact lens antenna configurations. At the design frequency f = 56.7 GHz (λ0 = 5.29 mm), the zoned fishnet metamaterial lens, designed to have a focal length FL = 9λ0, exhibits a refractive index n = −0.25. The focusing performance of the diffractive optical element is briefly compared with that of a non-zoned fishnet metamaterial lens and an isotropic homogeneous zoned lens made of a material with the same refractive index. Experimental and numerically-computed radiation diagrams of the fabricated zoned lens are presented and compared in detail with that of a simulated non-zoned lens. Simulation and experimental results are in good agreement, demonstrating an enhancement generated by the zoned lens of 10.7 dB, corresponding to a gain of 12.26 dB. Moreover, beam steering capability of the structure by shifting the feeder on...

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

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.

77-GHz High-Gain Bull’s-Eye Antenna With Sinusoidal Profile

A high-gain Bulls-Eye leaky-wave horn antenna working at 77 GHz with sinusoidal profile has been designed, fabricated, and experimentally measured. The influence of the number of periods on the gain and beamwidth is numerically investigated. Experimental measurements show a high gain of 28.9 dB, with low sidelobe level and a very narrow beamwidth in good agreement with results obtained from simulations.

Mechanical 144 GHz beam steering with all-metallic epsilon-near-zero lens antenna

An all-metallic steerable beam antenna composed of an e-near-zero (ENZ) metamaterial lens is experimentally demonstrated at 144 GHz (λ0 = 2.083 mm). The ENZ lens is realized by an array of narrow hollow rectangular waveguides working just near and above the cut-off of the TE10 mode. The lens focal arc on the xz-plane is initially estimated analytically as well as numerically and compared with experimental results demonstrating good agreement. Next, a flange-ended WR-6.5 waveguide is placed along the lens focal arc to evaluate the ENZ-lens antenna steerability. A gain scan loss below 3 dB is achieved for angles up to ±15°.

Soret fishnet metalens antenna.

At the expense of frequency narrowing, binary amplitude-only diffractive optical elements emulate refractive lenses without the need of large profiles. Unfortunately, they also present larger Fresnel reflection loss than conventional lenses. This is usually tackled by implementing unattractive cumbersome designs. Here we demonstrate that simplicity is not at odds with performance and we show how the fishnet metamaterial can improve the radiation pattern of a Soret lens. The building block of this advanced Soret lens is the fishnet metamaterial operating in the near-zero refractive index regime with one of the edge layers designed with alternating opaque and transparent concentric rings made of subwavelength holes. The hybrid Soret fishnet metalens retains all the merits of classical Soret lenses such as low profile, low cost and ease of manufacturing. It is designed for the W-band of the millimeter-waves range with a subwavelength focal length FL = 1.58 mm (0.5λ0) aiming at a compact antenna or radar systems. The focal properties of the lens along with its radiation characteristics in a lens antenna configuration have been studied numerically and confirmed experimentally, showing a gain improvement of ~2 dB with respect to a fishnet Soret lens without the fishnet metamaterial.

Zoned Fishnet Lens Antenna With Reference Phase for Side-Lobe Reduction

Reduction of first side-lobe level (SLL) and nulls in artificial fishnet metalenses is accomplished here by applying the reference phase concept along with the zoning technique. Higher focusing efficiency is achieved for a specific reference phase when comparing numerically and experimentally four different designs. For such best design, an improvement of the first SLL (~2.4 dB), first null (~13 dB), and gain (~1.77 dB) is achieved experimentally compared to the design without reference phase.

Tunable beam steering enabled by graphene metamaterials

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.

Wideband backscattering reduction at terahertz using compound reflection grating

Backscattering reduction is usually achieved by using either absorbers or diffractions gratings at the expense of a narrow bandwidth. In this paper, we propose a different strategy based on a metallic compound reflection grating (CRG). We demonstrate that this structure allows a strong and broadband (fractional bandwidth, FBW ≈57%) backscattering reduction in the terahertz (THz) range by efficiently transferring the incident energy to the diffracted modes. The design is analyzed in terms of equivalent circuit and numerical simulations and the results are corroborated by a manufactured prototype operating at 0.35 THz.

IR-Fresnel zone plate lens acting as THz antenna

A Fresnel Zone Plate Lens designed for the Mid-IR is modified for acting as a THz Antenna. This proposal is the base for a dual band detector consisting of a Silicon (Si) substrate with a quasi-spiral antenna detector working at THz frequencies which acts also as a modified Fresnel Zone Plate Lens for an IR detector. The focal properties of the proposed lens have been studied numerically, and its behavior as a submillimeter wave receiver has been demonstrated by a 3D full-wave simulator.