Broadband converging plano–concave lens

Abstract

A plano-concave lens with source-tailored geometric profile and transformational gradient index is proposed for broadband illumination. Such a design, capable of focusing and collimating the electromagnetic fields, fulfils the functionality of a converging lens and can also achieve a steerable beam and multiple beams efficiently. Nonresonant synthesis with a perforated dielectric plate and dielectric rod arrays is demonstrated for the lensing realization, promising a wide operating frequency band in the practical implementation.

Transformation-optical Fan-beam Synthesis

“…The physics behind is the generation of quasi-identically conformal modules in the distorted coordinates so that we are able to perform the further simplification accordingly. This operation is different from previous designs using QCTO, where the sizes of dielectric compositions of the transformational devices are limited to the half wavelength of travelling waves 20 21 22 23 27 . In this sense, it would be possible to propose much more concise designs with fewer dielectrics through manipulating the mesh generation concerning the original distorted space, and facilitate the final fabrications for the transformation-optics based devices.…”

“…Transformation optics 15 16 17 , as a promising strategy to control the electromagnetic fields since 2006, has been widely adopted to build up the new antenna system 18 19 20 21 22 23 24 . These proposals, either based on the 2D coordinate transformation to synthesize the flat lenses, or creating the 3D construction of the transformational media by rotating the 2D permittivity map around its symmetry axis 25 , have demonstrated the great efficiency to collimate the cylindrical wave from a primary line source or the spherical wave from an isotropic point source.…”

Multi-beam collimating meta-corners

“…However, the present literature generally deals with the reflectors and the lenses separately, and the multiple beams normally radiate in the half-space merely in the reflecting spectrum or solely in the transmitting regime. Clearly, using multiple transmissive meta-surfaces to enclose an omni-directional primary radiator in a polygonal geometry should be an effective way to generate multiple sharp beams with a coverage larger than 180-degrees [20,21]. However, these implementations normally require big structural volumes making the lensing devices fully distributed around the source rather than only located on one side of the feed.…”

Transformation of the corner: A shield cloak and a planar retro-reflector

“…However, these designs of the shield cloak composed of anisotropic materials from analytical transformation or the planar retro-reflector based on the phase tuning of microstrip patch arrays can only operate in a narrow frequency bandwidth. Quasi-conformal transformation optics (QCTO), in the meanwhile, has proved itself as a promising technology to build up compact all-dielectric devices [13][14][15][16], which are able to mimic the functionalities of the original devices in a broadband frequency range. For the aforementioned scattering corner, we could use QCTO to recover the reflected emission from the original corner reflector, by converting the curved surface into a flat sheet.…”