Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

'Magic' sphere for information transfer

24.08.2015

Professor at the Lomonosov Moscow State University made the «magic» sphere for information transfer

In several years - maybe in one or two decades, but maybe sooner or never - one of the existing problems will be solved in an original way: our computers, nanoantennas and other kinds of equipment will operate on the base of photons, rather than electrons. Even now we are practically prepared to accomplish this switch.


Spheres from experiments have sizes like 1-euro and 10-russian rubles coins.

Credit: Lomonosov Moscow State University

If it happens, the spheres studied by an international group of Russian, French and Spanish scientists will definitely be able to become one of the elementary components of new photonic devices. The results of the study were published in the latest issue of "Scientific Reports," which is a part of the prestigious Nature Publishing Group.

The potentialities of the conventional electronic computers are going to be exhausted. During last four decades, Moore's law (according to which computer's processor speed doubles every 18 months) was fulfilled due to increasing of the operating frequency of a single processor.

Now the same result is reached by means of the parallel computing - we have dual-core processors as well as quad-core ones. It means that single-core processors are not able to cope with the computation speed demanded; moreover, it is not possible to increase this speed anymore because modern computers' processor operating frequency is close to the theoretical limit.

The process of multiplying the number of cores is also not endless: by all accounts it will soon come to the end. That's why plenty of research teams all around the world are working on the creation of super-fast optical systems, which would be able to replace the electronic computers.

On one hand, such systems should be as small as possible. On the other hand, optical radiation has its own scale - the wavelength (in the visible range of the spectrum it is about 0.5 micrometers). This scale is too big to be implemented in modern electronic devices with ultra-dense arrangement of elements. In order to compete with such electronic devices, optical systems should work on scales much shorter than the wavelengths.

These problems fall within the domain of modern discipline, called subwavelength optics. The aim of subwavelength optics is to manipulate with electromagnetic radiation on scales shorter than its wavelength -- in other words, to do the things, which were considered as conceptually impossible in the traditional optics of lenses and mirrors.

Until recently subwavelength optics laid great hopes on the effects related to interactions of light with the, so-called, plasmons -- collective oscillations of free electron gas in metals. In the case of metal particles with sizes about 10 nm the frequencies of the oscillations of the free electron gas fall within the range of the optical band. If such a particle is irradiated with an electromagnetic wave, whose frequency is equal to one of the particle's plasmon oscillation frequencies a resonance occurs. At the resonance, the particle acts as a funnel, which "grabs" the electromagnetic wave's energy from the external environment and converts it into the energy of the electronic gas oscillations. This process can be accompanied with a wide range of very interesting effects that, in principle, could be employed in various applications.

Unfortunately, the best part of the expectations related to the plasmonics has not been justified. The fact is that even very good electric conductors (for example, copper or platinum) exhibit large electric resistance when the frequency of the electric current becomes of the same order of magnitude as that of the visible light. Therefore, as a rule, the plasmon oscillations are strongly damped, and the damping kills the useful effects that could be made use of.

That's why recently, scientists paid their attention to dielectric materials with high refractive index. There are no free electrons in these materials because all of them are connected with their atoms; and the impact of light does not induce conduction current. At the same time, electromagnetic wave affects electrons inside the atom and shifts them from the equilibrium positions. As a result, atoms acquire induced electric moment; this process is called "polarization".

The higher the degree of polarization is, the higher the refractive index of the material is. It turned out that when a sphere made of a material with high refraction index interacts with light, the result of this interaction to a large extent resembles the above-described plasmon resonance in metals with one (but very important) exception: a wide range of dielectric materials -- as distinct from metals -- have weak damping at the optical frequencies. We often use this property of dielectrics in our everyday life - for example, weak damping at the optical frequencies is the key for the transparency of glass.

An ancient work of Professor Michael Tribelsky (Mikhail Tribel'skii), [1]Faculty of Physics, M.V. Lomonosov Moscow State University, and Moscow State University of Information Technologies, Radioengineering and Electronics MIREA, gave the initial impulse to the research described above. The scientist says: "If we use the language of quantum physics while speaking about the plasmon excitation, we can say that a quantum of light, photon is converted into a quantum of plasmon oscillations. In the middle of 80th I got the following idea: since all processes in quantum mechanics are reversible, the inverted process of the plasmon-to-photon conversion should exist too.

Then, I arrived at the conclusion that a new type of light scattering exists. This was the case indeed. Moreover, it occurred that this new type of light scattering has very little in common with the described in all textbooks Rayleigh scattering". As a result, paper "Resonant scattering of light by small particles", Tribel'skii M.I., Sov. Phys. JETP 59[2], 534 (1984): http://www.jetp.ac.ru/cgi-bin/dn/e_059_03_0534.pdf came out. However, in 1984 this work could not attract the attention of scientists, because nanotechnologies did not exist yet.

The first citation of this paper occurred in 2004 - exactly 20 years after its publication. Nowadays, this type of scattering, named "anomalous," is widely acknowledged. Unfortunately, even in the case of the anomalous scattering, once again, we face the fatal role of dissipation. In order to observe the anomalous scattering it is necessary to use metals with very weak damping at optical frequencies.

The very natural question in this case is: if we take the advantage of the weak damping of dielectrics, will the sphere made of dielectric materials with high refraction index be able to demonstrate the effects which cannot be observed in the case of plasmon resonances in metals with strong damping? To answer the question Professor Tribelsky's laboratory (Faculty of Physics, M.V. Lomonosov Moscow State University) began a carry out a joint research with French and Spanish colleagues. Scientists experimented with a dielectric sphere with a diameter about 2 cm, made of special ceramics, and "taught" it to redirect the incident electromagnetic waves in a desired manner. Moreover, the directionality of the scattering may be controlled and changed dramatically just by fine tuning of the frequency of the incident wave.

According to Tribelsky's explanation, this sphere has rather narrow resonance lines related to its polarization oscillations. In a sense, it is quite analogous to a metal sphere, which has the resonance frequencies related to the oscillations of the free electron gas. Every line corresponds to the excitation of a particular oscillation mode, called harmonics or partial modes.

Every harmonic is characterized by a fixed dependence between the scattering intensity and the scattering angle. This dependence is determined by the nature of a given harmonic. The sphere's total scattering field is a sum of the contributions of every harmonic (partial wave). Partial waves interfere with each other. The narrow width of these lines allows to excite partial modes selectively and to control the interference. This, in turn, allows redirecting the incident radiation in a desired way. That's it! The controlled manipulation with the radiation is achieved.

However, why do we speak about nanoscales if the sphere's diameter is about 2 cm? That's just the point. Prof. Tribelsky says: "I can freely speak about the experimental beauty of this work as I'm a theoretician. I just participated in the planning of the experiment, while the entire difficult experimental work was done by my French colleagues.

As for the experimental beauty of this work, it is in the following: with the help of the microwave radiation - similar to the one used in a mini oven -- we have managed to simulate on a centimeter scale all the processes occurred on a nanoscale with the visible light. It is widely known: if we have two objects of the same shape but of different sizes and with the same refractive index, they will scatter the electromagnetic waves in the same way, provided the ratio of objects' linear dimensions to the wavelength is the same for both the objects. This was the idea of our experiments. However, the way from the idea to the results was very difficult. It's sufficed to say that the researchers managed to separate the desired signal from background whose amplitude sometimes was 3000 times larger (!) than that of the signal."

Bearing in mind possible practical applications of the obtained results, it is important to stress that the fabrication technique of such nanospheres for manipulation of optical and near infrared radiation is rather cheap and simple. It does not require any "exotic," expensive materials, and/or sophisticated equipment. Besides the optical computers (which, nowadays, yet stay in the sphere of virtual reality), nanoscale spheres described in the paper by Tribelsky and co-authors can be used in the wide range of different fields: telecommunication systems; recording, processing and storing of information; diagnosis and treatment of different diseases including oncological, etc.

Media Contact

Vladimir Koryagin
science-release@rector.msu.ru

http://www.msu.ru 

Vladimir Koryagin | EurekAlert!

More articles from Information Technology:

nachricht New software speeds origami structure designs
12.10.2017 | Georgia Institute of Technology

nachricht Seeing the next dimension of computer chips
11.10.2017 | Osaka University

All articles from Information Technology >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Electrode materials from the microwave oven

19.10.2017 | Materials Sciences

New material for digital memories of the future

19.10.2017 | Materials Sciences

Physics boosts artificial intelligence methods

19.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>