New metamaterials: light under control
A lot of reports about "metamaterials" (in quotation marks, because the definition is starting to blur) make us think of them as almost a panacea for all the problems, pains and limitations that the modern world of technology faces. The most interesting concepts lately concern optical computers and virtual reality.
in respect of hypothetical computers of the futureas an example, one can cite the research of specialists from the Israeli TAU University in Tel Aviv. They are designing multilayer nanomaterials that should be used to create optical computers. In turn, researchers from the Swiss Paul Scherrer Institute built a three-phase substance from a billion miniature magnets capable of simulate three aggregate states, by analogy with water.
What can it be used for? The Israelis want to build. The Swiss talk about data transmission and recording, as well as spintronics in general.
A three-phase metamaterial made of minimagnets that mimics the three states of water.
Photons on demand
Research by scientists at the Lawrence Berkeley National Laboratory at the Department of Energy may lead to the development of optical computers based on metamaterials. They propose to create a kind of laser framework that can capture certain packages of atoms in a certain place, creating a strictly designed, controlled light based structure. It resembles natural crystals. With one difference - it is almost perfect, no defects are observed in natural materials.
Scientists believe that they will not only be able to tightly control the position of groups of atoms in their "light crystal", but also actively influence the behavior of individual atoms using another laser (near infrared range). They will make them, for example, on demand emit a certain energy - even a single photon, which, when removed from one place in the crystal, can act on an atom trapped in another. It will be a kind of simple exchange of information.
The ability to quickly release a photon in a controlled manner and transfer it with little loss from one atom to another is an important information processing step for quantum computing. One can imagine using entire arrays of controlled photons to perform very complex calculations - much faster than using modern computers. Atoms embedded in an artificial crystal could also jump from one place to another. In this case, they themselves would become information carriers in a quantum computer or could create a quantum sensor.
Scientists have found that rubidium atoms are ideal for their purposes. However, barium, calcium, or cesium atoms can also be captured by an artificial laser crystal because they have similar energy levels. To make the proposed metamaterial in a real experiment, the research team would have to capture a few atoms in an artificial crystal lattice and keep them there even when excited to higher energy states.
Virtual reality without optical defects
Metamaterials could find useful applications in another developing area of technology -. Virtual reality has many different limitations. The imperfections of optics known to us play a significant role. It is practically impossible to build a perfect optical system, because there are always so-called aberrations, i.e. wave distortion caused by various factors. We are aware of spherical and chromatic aberrations, astigmatism, coma and many, many other adverse effects of optics. Anyone who has used virtual reality sets must have dealt with these phenomena. It is impossible to design VR optics that are lightweight, produce high-quality images, have no visible rainbow (chromatic aberrations), give a large field of view, and be cheap. This is just unreal.
That is why VR equipment manufacturers Oculus and HTC use what are called Fresnel lenses. This allows you to get significantly less weight, eliminate chromatic aberrations and get a relatively low price (the material for the production of such lenses is cheap). Unfortunately, refractive rings cause w Fresnel lenses a significant drop in contrast and the creation of a centrifugal glow, which is especially noticeable where the scene has a high contrast (black background).
However, recently scientists from Harvard University, led by Federico Capasso, managed to develop thin and flat lens using metamaterials. The nanostructure layer on glass is thinner than a human hair (0,002 mm). Not only does it not have the typical drawbacks, but it also provides much better image quality than expensive optical systems.
The Capasso lens, unlike typical convex lenses that bend and scatter light, changes the properties of the light wave due to microscopic structures protruding from the surface, deposited on quartz glass. Each such ledge refracts light differently, changing its direction. Therefore, it is important to properly distribute such a nanostructure (pattern) that is computer-designed and produced using methods similar to computer processors. This means that this type of lens can be produced in the same factories as before, using known manufacturing processes. Titanium dioxide is used for sputtering.
It is worth mentioning another innovative solution of "meta-optics". metamaterial hyperlensestaken at the American University at Buffalo. The first versions of hyperlenses were made of silver and a dielectric material, but they only worked in a very narrow range of wavelengths. The Buffalo scientists used a concentric arrangement of gold rods in a thermoplastic case. It works in the visible light wavelength range. The researchers illustrate the increase in resolution resulting from the new solution using a medical endoscope as an example. It usually recognizes objects up to 10 nanometers, and after installing hyperlenses, it "drops" down to 250 nanometers. The design overcomes the problem of diffraction, a phenomenon that significantly reduces the resolution of optical systems - instead of wave distortion, they are converted into waves that can be recorded in subsequent optical devices.
According to a publication in Nature Communications, this method can be used in many areas, from medicine to single molecule observations. It is appropriate to wait for concrete devices based on metamaterials. Perhaps they will allow virtual reality to finally achieve real success. As for "optical computers", these are still rather distant and vague prospects. However, nothing can be ruled out...
