The scientific journal Journal of Optics has dedicated the cover of its special issue on mid-infrared and terahertz photonics to the work carried out by researchers from the Public University of Navarre: Víctor Pacheco Peña, Víctor Torres, Miguel Beruete, and Miguel Navarro-Cía (a graduate currently working at Imperial College London), along with Nader Engheta (University of Pennsylvania), one of the world's leading experts in metamaterials. In their research, they have proposed several devices capable of redirecting electromagnetic waves with efficiencies approaching 100%.
To explain their work, they offer the following example: “If we shine a flashlight on a wall with a hole in it, experience tells us that the larger the hole, the more light passes through. However, if we now fill the hole with an ENZ metamaterial, something happens that seems to defy logic: the smaller the hole, the more light passes through. This phenomenon has tremendous practical implications because it opens new avenues for the miniaturization of multiple components and the control of light.”.
Metamaterials are artificial materials with properties that go beyond those of natural elements. To understand how they work, we can look to nature itself: while natural elements acquire their physical properties from the atoms that compose them and the way they are arranged, metamaterials use natural elements, such as small metallic fragments, that fit together like pieces of a construction set to artificially synthesize properties impossible to obtain otherwise. Initially proposed for the control of electromagnetic radiation, their use has now become widespread and extended to other areas such as mechanical waves (sound, for example).
The work proposes various devices capable of redirecting electromagnetic waves with efficiencies close to 100%
The reviewed work proposes several compact devices, consisting of rectangular metal tubes with extremely narrow openings, designed to redirect electromagnetic waves with efficiencies approaching 100%. These openings emulate an ENZ metamaterial (Epsilon Near Zero, meaning permittivity close to zero), so they do not need to be filled with anything to obtain surprising properties.
Surprising properties
Among electromagnetic metamaterials, the aforementioned ENZs allow for light supercoupling, tunneling, and energy confinement in infinitely small spaces. “Returning to the initial example,” the authors of the paper explain, “supercoupling means that all the light will be transferred from one side of the wall to the other for any shape of hole we want to make; tunneling means that light will pass through a hole of any length, no matter how long we want to make it; and energy confinement is due to the fact that light is transferred even for very small holes, thus compressing the energy inside the hole enormously.”.
This work has demonstrated, both theoretically and through simulations, the operation of beam diverters and power dividers for terahertz waves, which are of great interest given their enormous potential in sectors such as security, biomedical engineering, pharmaceuticals, aerospace, and others. The authors of this research are currently working on experimental confirmation of the study. In this regard, they emphasize that "this represents another milestone in an international initiative that has been underway for almost four years.".
Source: SINC Agency
