Experimental and theoretical verification of focusing in a large, periodically loaded transmission line negative refractive index metamaterial

Abstract

We have previously shown that a new class of Negative Refractive Index (NRI) metamaterials can be constructed by periodically loading a host transmission line medium with inductors and capacitors in a dual (high-pass) configuration. A small planar NRI lens interfaced with a Positive Refractive Index (PRI) parallel-plate waveguide recently succeeded in demonstrating focusing of cylindrical waves. In this paper, we present theoretical and experimental data describing the focusing and dispersion characteristics of a significantly improved device that exhibits minimal edge effects, a larger NRI region permitting precise extraction of dispersion data, and a PRI region consisting of a microstrip grid, over which the fields may be observed. The experimentally obtained dispersion data exhibits excellent agreement with the theory predicted by periodic analysis, and depicts an extremely broadband region from 960MHz to 2.5GHz over which the refractive index remains negative. At the frequency at which the theory predicts a relative refractive index of -1, the measured field distribution shows a focal spot with a maximum beam width under one-half of a guide wavelength. These results are compared with field distributions obtained through mathematical simulations based on the plane-wave expansion technique, and exhibit a qualitative correspondence. The success of this experiment attests to the repeatability of the original experiment and affirms the viability of the transmission line approach to the design of NRI metamaterials.

Negative Refraction by Photonic Crystal

“…Experimental observation of negative refraction in meta-materials is verified by Shelby et al [5]. Recently negative refraction has been the subject of considerable interest which may provide the possibility of a variety of novel applications of very interesting new phenomena like the superlens effect [6][7][8][9][10]. A negative refractive index arises in meta-materials that have simultaneous negative permittivity ε and permeability µ, where in homogeneities are much smaller than the wavelength of the incoming radiation and it has been demonstrated at microwave wavelengths [11][12][13].…”

Focusing Ultrasound with an Acoustic Metamaterial Network

“…The successful demonstration of electromagnetic (EM) superlens [7][8][9][10] has inspired the search for the analogous acoustic negative-index lens. In fact, phononic crystals [11][12][13][14][15] were first investigated to develop negative-refractive devices for sound waves.…”

“…Given this value, the lumped circuit model is a valid approximation for the distributed acoustic system with only 10% error [25]. Following the approach of EM circuit analysis [8][9][10], the effective density and compressibility of this network can be expressed in the form as The right half part of the sample is the dual configuration of the left half part, in which there is an array (40×40) of orifices connected with channels. The volume of one section of the main channel is designed as around ten times of that of the orifice.…”

Metamaterial-Based Flat Lens: Wave Concept Iterative Process Approach

“…6), we placed a source cell at the third line at a distance from the first interface of the metamaterial order d1 = 2d (or corresponding to two cell lines), and the second interface [22] is located at a distance of 2d from the first interface. The source image is focused at a distance of 2d behind the second interface to validate this study [23]. We observe (in Fig.…”