Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists count microscopic particles without microscope

10.08.2016

Scientists from Russia and Australia have put forward a simple new way of counting microscopic particles in optical materials by means of a laser. A light beam passing through such a material splits and forms a characteristic pattern consisting of numerous bright spots on a projection screen.

The researchers found that the number of these spots corresponds exactly to the number of scattering microscopic particles in the optical material. Therefore, the structure and shape of any optical material can be determined without resorting to the use of expensive electron or atomic-force microscopy. According to the researchers, the new method will help design optical devices much faster. The work was published in Scientific Reports.


Experimentally obtained and simulated diffraction patterns for a sample.

Credit: ITMO University

The production of optical circuits requires devices that can amplify optical signals, bring them into focus, rotate and change their type of motion. Ordinary lenses cannot cope with these tasks at nanoscale, so scientists are working with artificial optical materials - photonic crystals and metamaterials, which can control the propagation of light in most extraordinary ways. However, fabricating optical materials with desired properties is a laborious process that needs constant improvement.

The scientists from ITMO University, Ioffe Institute, and Australian National University for the first time suggested analyzing the structure of photonic crystals using optical diffraction method, that is, by looking at the light pattern generated while the sample is exposed to a laser beam. The study has shown that the number of these spots is equal to the number of scattering microscopic particles in the sample structure. Previously, such small particles could only be seen and counted with powerful and expensive electron or atomic-force microscopes.

"The light senses heterogeneity," says Mikhail Rybin, first author of the paper, senior researcher at the Department of Nanophotonics and Metamaterials at ITMO University. "Depending on the shape and relative position of the scatterers, the light wave continues to propagate differently behind the sample. In other words, the structure of the sample affects the diffraction pattern, which will be projected on the screen. We found out that looking at the pattern, it is possible to determine the precise number of scatterers in the material. This helps understand not only the type of the sample lattice (square, triangular), but also to establish its structure (20 to 20 particles, or 30 to 15) just by counting light spots on the screen".

The new method is a much more affordable alternative to expensive electron or atomic-force microscopy and in this case, does not spoil the sample. "Even a schoolboy can buy a laser pointer, adapt a small lens to focus the light better, fix the sample and shine a laser beam on it," notes Mikhail Rybin. "In addition, our method makes it possible to study optical materials without changing their structure in contrast to electron microscopy, where the sample surface has to be covered by conductive metal layer, which impairs optical properties of the sample".

The new method has already enabled scientists to investigate the transition between two main classes of optical materials: photonic crystals and metasurfaces. In the study, they have determined the lattice parameters, which define whether the light perceives the material as a two-dimensional photonic crystal or a metasurface.

In both classes, the scattering particles (rings, balls, cylinders of 200-300 nanometers) are arranged in a flat lattice. However, in case of two-dimensional photonic crystal, the light perceives the sample as a set of separate particles. Therefore, passing through it the light generates a fancy pattern on the screen behind the sample. In case of metasurfaces, the light perceives the sample as homogenous. The screen shows only one bright spot indicating that the scattering particles are located close enough to each other, such that the light does not see them as separate particles and passes through the sample without splitting.

In order for the light beam to pass through a metasurface, the distance between the particles has to be smaller than the wavelength of light. Calculations show that for some structures it is needed to produce a lattice where the distance between particles is 2 to 3 times smaller than the wavelength of light. Often, however, meta-properties can manifest themselves at larger distances between the particles. It is important to find the maximum allowable distance, since reducing the structure by one single nanometer makes the technology more expensive.

It turned out, for example, that for the light with a wavelength of 530 nanometers (green color), the distance of 500 nanometers between the scattering particles is already enough. "A green light beam perceives the structure with a period of 500 nanometers as a homogenous material. Therefore, sometimes it is not necessary to fabricate a lattice with a period of much smaller than a wavelength because producing larger structures is much easier from technological standpoint. For one wavelength, the material will act as a photonic crystal and as a metasurface for another. That is why designing such structures, we can evaluate maximum lattice period with laser," concludes Mikhail Rybin.

###

ITMO University (Saint Petersburg) is a national research university, the leading Russian university in the field of information and photonic technologies. The university is the alma mater of winners of numerous international programming competitions: ACM ICPC (the only six-time world champions), Google Code Jam, Facebook Hacker Cup, Yandex Algorithm, Russian Code Cup, Topcoder Open etc. Research priorities: IT, photonic technologies, robotics, quantum communication, translational medicine, urban studies, art&science, and science communication. Starting from 2013, the university is a member of Project 5-100, which unites 15 top Russian universities to improve their status in the international research and education arena.

Media Contact

Dmitry Malkov
dvmalkov@corp.ifmo.ru
7-953-377-5508

 @spbifmo_en

http://en.ifmo.ru/ 

Dmitry Malkov | EurekAlert!

More articles from Physics and Astronomy:

nachricht Further Improvement of Qubit Lifetime for Quantum Computers
09.12.2016 | Forschungszentrum Jülich

nachricht Electron highway inside crystal
09.12.2016 | Julius-Maximilians-Universität Würzburg

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>