Simulation and testing of a graded negative index of refraction lens

Abstract

A gradient index (GRIN) lens using a negative index of refraction material (NIM) has been designed and tested. The GRIN lens was fabricated using a NIM slab with a variable index of refraction perpendicular to the propagation direction. Ray tracing calculations based on the isotropic Eikonal equation determined the index of refraction gradient required for a given focal length. An electromagnetic code was then used to design the required ring and wire unit cells. Finally, the index of refraction was approximated using ten discrete steps in an effective medium simulation for the GRIN lens that agreed with the experimental measurements.

A broadband low-reflection metamaterial absorber

“…For the purpose of our study, we need a retrieval method capable of characterizing the scattering off the absorbing media, as opposed to a method that describes in detail the physics of how individual cells behave. We therefore chose a relatively simple retrieval algorithm 19 that was shown to be successful in the design of various metamaterial devices, [22][23][24] and which implicitly accounts for complex phenomena such as spatial dispersion or coupling between constitutive elements. This method is especially suitable for experimental retrievals and relies on estimating the nonlocal effective refractive index and impedance from reflection and transmission measurements.…”

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

“…1,4 Therefore, depending on the value of n, a converging lens would require different geometrical profiles such as ellipses, hyperbolas, and parabolas. Many NRI metamaterial lenses based on the classical arrangement of split ring resonators and wires with planoconcave 21 and cylindrical profiles 22 have been reported. However, the operation frequency of these lenses is limited to microwaves due to their increasing losses with frequency and saturation of the magnetic response.…”

[INVITED] Epsilon-near-zero metalenses operating in the visible

“…In this technique, both (input and output) faces of the metalens are planar and the required phase distribution to focus the incoming plane-wave should be introduced by each waveguide in the array. 15,16,33 As it has been explained in section 2, by correctly engineering h x , different values of propagation constant and phase will be obtained. The phase that each waveguide should introduce for optical focusing can be calculated as follows: 15,34 …”