Metamaterial || Metasurface || History of metamaterials

Metamaterial || Metasurface || History of metamaterials 

To the best of our knowledge, the first investigation into the idea of "artificial" materials dates back to 1898, when Jagadis Chunder Bose performed the first microwave experiment on twisted structures—geometries that, by modern nomenclature, were effectively artificial chiral components. In order to create "fake" chiral media, Lindman embedded several tiny wire helices with random orientations into a host medium in 1914. Kock created lightweight microwave lenses in 1948 by placing conducting spheres, discs, and strips in regular patterns and precisely adjusting the artificial media's effective refractive index. Since then, a lot of researchers throughout the world have been studying artificial complex materials. In recent years, new ideas in synthesis and inventive fabrication methods have made it possible to create composite materials and structures that mimic the responses of known materials or that qualitatively have brand-new, physically realisable response functions that don't naturally occur or may not be readily available. In theory, it is possible to create these metamaterials by embedding diverse constituents and inclusions in host media that have novel geometric structures. Numerous research teams around the world have researched different kinds of electromagnetic composite media, including double-negative (DNG) materials, chiral materials, omega media, wire media, bi anisotropic media, linear and nonlinear media, and local and nonlocal media, to name a few. It is common knowledge that electromagnetic waves interact with inclusions in particulate composite media, causing electric and magnetic moments that change the bulk composite "medium's" macroscopic effective permittivity and permeability. By embedding artificially created inclusions in a chosen host medium or on a chosen host surface, metamaterials can be created. This gives the designer access to a wide range of independent parameters (or degrees of freedom), such as the characteristics of the host materials and the size, shape, and composition of the inclusions and the density, arrangement, and alignment of these inclusions—to work with in order to engineer a metamaterial with specific electromagnetic response functions not found in each of the individual constituents. All of these design parameters can play a key role in the final outcome of the synthesis process. Among these, the geometry (or shape) of the inclusions is one that can provide a variety of new possibilities for metamaterials processing. Recently, the idea of complex materials in which both the permittivity and the permeability possess negative real values at certain frequencies has received considerable attention. In 1967, Veselago conducted a theoretical study on the propagation of plane waves in a material whose permittivity and permeability were both believed to be negatively polarised. In contrast to the case of plane wave propagation in typical simple media, his theoretical analysis demonstrated that for a monochromatic uniform plane wave in such a medium, the direction of the Poynting vector is antiparallel to the direction of the phase velocity. Recently, Smith, Schultz, and their team created a composite media for the microwave regime and experimentally proved that it had anomalous refraction.

 Many names and terminologies, such as "left-handed" media and media with negative refractive index, have been proposed for metamaterials with negative permittivity and permeability. “backward-wave media” (BW media)  and “double-negative (DNG)” metamaterials, to name a few. Many research groups all over the world are now studying various aspects of this class of metamaterials, and several ideas and suggestions for future applications of these materials have been proposed. It is well known that the response of a system to the presence of an electromagnetic field is determined to a large extent by the properties of the materials involved. We describe these properties by defining the macroscopic parameters permittivity ε and permeability µ of these materials. This allows for the classification of a medium as follows. A medium with both permittivity and permeability greater than zero (ε > 0, µ > 0) will be designated a double positive (DPS) medium. Most naturally occurring media (e.g., dielectrics) fall under this designation. A medium with permittivity less than zero and permeability greater than zero (ε < 0, µ > 0) will be designated an epsilon-negative (ENG) medium. In certain frequency regimes, many plasmas exhibit this characteristic. For example, noble metals (e.g., silver, gold) behave in this manner in the infrared (IR) and visible frequency domains. A medium with permittivity greater than zero and permeability less than zero (ε > 0, µ < 0) will be designated a mu negative (MNG) medium. In certain frequency regimes, some gyro tropic materials exhibit this characteristic. Artificial materials have been constructed that also have DPS, ENG, and MNG properties. A medium with both the permittivity and permeability less than zero (ε < 0, µ < 0) will be designated a DNG medium. To date, this class of materials has only been demonstrated with artificial constructs.