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Our paper on “Far-field imaging beyond the diffraction limit using waves interference” was accepted for publication in IEEE Journal of Light Wave Technology.

Abstract:

Due to the wave nature of light, resolution of optical imaging systems is limited to approximately half of the wavelength. The reason behind this limitation, known as diffraction limit, is the loss of information contained in evanescent waves at the far-field region. Here, we propose a new method to retrieve the information contained in evanescent waves in far field region resulting in a novel sub-wavelength imaging technique which can go beyond the diffraction limit. We theoretically prove that using interference of waves, between the target field and reference and reconstruction waves, one can apply a shift to the angular spectrum of the target field and convert a range of evanescent waves into propagating modes. Moreover, we demonstrate how these converted waves can be distinguished in far-field from other existing modes. Unlike previously developed sub-wavelength imaging techniques, the proposed method does not require neither fluorescent materials nor complex nano-structures to realize evanescent-to-propagating wave conversion. The performance of the method is numerically investigated illustrating a resolution of one-seventh of the working wavelength, which is much beyond the diffraction limit. The proposed technique can significantly simplify sub-wavelength imaging paving the road to develop practical low cost superresolution imaging systems.

Link:

https://ieeexplore.ieee.org/document/8960340

Our paper on “Graphene-based low side-lobe microwave horn antenna,” was accepted for publication in IET Microwaves, Antennas & Propagation

Abstract:

In this paper, a novel method is proposed to control and reduce the side-lobe level (SLL) of the pyramidal horn antennas. In this method, graphene sheets are deposited on the antenna walls to taper the aperture field leading to pattern engineering with the goal of the side-lobe level reduction. In essence, graphene sheet acts as a high impedance surface (HIS) and hinders electromagnetic power from reaching to the horn antenna aperture edges, in such a way that the diffraction phenomenon could be drastically diminished. The proposed design is numerically analyzed and optimized using full wave 3D simulation methods. Numerical full-wave results illustrate more than 17.6 dB reduction in the side lobe level of the proposed antenna.

Graphene based low sidelob horn antenna

Link:

https://ieeexplore.ieee.org/document/8826046

Our paper on “Far Field Subwavelength Imaging using Phase Gradient Metasurfaces” was accepted for publication in IEEE Journal of Light Wave Technology

Abstract

Imaging subwavelength features of an object is in close relationship with extracting information included in evanescent waves scattered from the object. These evanescent waves decay exponentially with distance, therefore, they can not be captured at far-field, resulting in a resolution limited image of the object. Here, we propose a far field imaging technique based on gradiant metasurfaces, with ability to provide an image of subwavelength features. In this technique, gradient metasurfaces are used to convert evanescent waves scattered by subwavelength features into propagating waves resulting in a resolution beyond the diffraction limit. The performance of the proposed imaging technique is evaluated using full wave numerical analysis and the results validate its capability for imaging beyond the diffraction limit.

Link:

https://ieeexplore.ieee.org/document/8657738

Our paper on “Topological Plasmonic Edge States in a Planar Array of Metallic Nanoparticles” was accepted for publication in Nanophotonics

Abstract:

Photonic topological insulators (PTIs) are electromagnetic structures with highly robust uni-directional edge states, originating from their non-trivial bulk band topology. Here, we propose a plasmonic PTI that supports highly confined one-way edge states capable of transporting deep subwavelength optical frequency plasmons through arbitrary paths without back-scattering. The structure consists of a simple planar array of coupled plasmonic nanoparticles arranged in a perturbed honeycomb lattice, that exhibits non-trivial band topology. The operation frequency of the emergent edge states is shown to be independent of the lattice constant allowing for the miniaturization of the structure. As a high frequency PTI with a simple and planar design, this structure is compatible with well-established integrated nanofabrication technologies and may find application in planar, compact and topologically robust integrated nanophotonic devices.

Link:

https://www.degruyter.com/view/j/nanoph.2019.8.issue-5/nanoph-2018-0230/nanoph-2018-0230.pdf