|Posted on March 4, 2019 at 9:10 AM|
Ph.D. student Oshri’s paper (in collaboration with Rafael Advanced Defense Systems Ltd.) “Experimental demonstration and in-depth investigation of analytically designed anomalous reflection metagratings” was recently published in Physical Review B.
The paper verifies experimentally the analytical scheme we have previously developed for designing realistic (printed-circuit-board fabrication-ready) metagratings for perfect anomalous reflection. These metagratings feature only a single simple element (single degree of freedom) per period, yet couple 96% of the scattered power towards the desirable anomalous reflection mode. Multifunctionality and multichannel reflection features are observed, and important experimental aspects, such as the merits of the beam-integration technique for evaluating the coupling efficiency, as well as the origin of losses, are explored and discussed in detail.
|Posted on December 25, 2017 at 2:05 AM|
Our recent paper “Negative index effects from a homogeneous positive index prism” was just published in EPJ-Applied Metamaterials.
The paper sheds light on experiments conducted to verify effective negative index of refraction in artificial metamaterials. The investigation shows that certain observations typically associated with negative index effects, but can actually arise from a homogeneousn positive index (natural) material, if deformed to the usual cerrated prism configuration applied in metamaterial experiments. Thus, experimental evidence for negative index effects should be carefully examined in order to unambiguously verify the metamaterial properties.
|Posted on November 24, 2017 at 1:45 AM|
Our recent paper “Unveiling the Properties of Metagratings via a Detailed Analytical Model for Synthesis and Analysis” has just been published in Physical Review Applied, and was chosen as “Editors’ Suggestion”.
The paper explores the novel concept of metagratings, periodic arrays consisting of one or two subwavelength polarizable particles (meta-atoms) per period. Surprisingly, despite the utmost simplicity, these structures allow highly-efficient implementation of intricate beam-manipulating functionalities, such as perfect anomalous reflection. In our manuscript, we rigorously investigate metagratings based on capacitively loaded conduting wires for perfect wide-angle beam splitting, via a detailed analytical model. We show that based on this architecture, compatible with printed-circuit-board (PCB) manufacturing techniques, the synthesis can be completed almost completely analytically, prescribing the copper trace geometry required for reaching unitary coupling efficiencies.
Furthermore, the formulation allows analytical examination of the device susceptibility to conductor losses, fabrication imperfections, and frequency shifts. This examination reveals that metagratings feature distinct preferable working points, in which the sensitivity to these non-idealities is minor, directly realted to fundamental interference processes taking place within the device.
|Posted on December 19, 2016 at 9:45 AM|
Our recent work, suggesting to harness auxiliary fields to facilitate advanced metasurface-based beam manipulations, was published in Physical Review Letters. In this Letter, we show that certain basic diffraction engineering problems (e.g., beam splitting, engineered reflection) feature mode interference that does not allow local power conservation. The latter is required to generate passive lossless metasurface designs to implement the desirable functionalities. Thus, recent reports that examined these problems, marked them as significant challenges, and suggested approximated solutions or exotic ones.
In the manuscript, we propose a new paradigm to tackle these challenges. The key concept involves the utilization of evanescent modes to manipulate the flow of real power, in both lateral and longitudinal directions, assisting the establishment of local power conservation. Being evanescent, these auxiliary fields do not affect the device functionality in the far field, while guaranteeing a passive and lossless solution.
We demonstrate this concept for the problems of wide-angle beam splitting and perfect engineered reflections, showing that both functionalities can be implemented using standard, local, reciprocal, passive, and lossless omega-bianisotropic meta-atoms. Interestingly, the auxiliary fields are not bound to any specific form; although the designed metasurfaces are periodic, in certain cases the auxiliary fields are not Floquet-Bloch modes of the incident fields.