A group of physicists from Russia, Sweden, and the U.S. has demonstrated a highly unusual optical effect: They managed to "virtually" absorb light using a material that has no light-absorbing capacity. The research findings, published in Optica, break new ground for the creation of memory elements for light.
The absorption of electromagnetic radiation -- light, among other things -- is one of the main effects of electromagnetism. This process takes place when electromagnetic energy is converted to heat or another kind of energy within an absorbing material (for instance, during electron excitation).
This is a schematic of a virtual light absorption process: A layer of a transparent material is exposed to light beams from both sides, with the light intensity increasing in time. Image courtesy of the researchers.
Credit: MIPT Press Office
This is virtual absorption effect in a thin layer of a transparent material. The dotted line indicates the amplitude of a time-dependent incident wave; the solid line is the amplitude of a scattered signal that comprises both incident and transmitted waves. The scattered signal is absent up to t = 0, suggesting that the incident wave energy is perfectly "locked" in the layer. Image courtesy of the researchers.
Credit: MIPT Press Office
Coal, black paint, and carbon nanotube arrays -- also known as Vantablack -- look black because they absorb the energy of the incident light almost completely. Other materials, such as glass or quartz, have no absorbing properties and therefore look transparent.
In their theoretical research, the results of which were published in the journal Optica, the physicists managed to dispel that simple and intuitive notion by making a completely transparent material appear perfectly absorbing. To achieve that, the researchers employed special mathematical properties of the scattering matrix -- a function that relates an incident electromagnetic field with the one scattered by the system.
When a light beam of time-independent intensity hits a transparent object, the light does not get absorbed but is scattered by the material -- a phenomenon caused by the unitary property of the scattering matrix. It turned out, however, that if the intensity of the incident beam is varied with time in a certain fashion, the unitary property can be disrupted, at least for some time. In particular, if the intensity growth is exponential, the total incident light energy will accumulate in the transparent material without leaving it (fig. 1). That being the case, the system will appear perfectly absorbing from the outside.
To illustrate the effect, the researchers examined a thin layer of a transparent dielectric and calculated the intensity profile required for the absorption of the incident light. The calculations confirmed that when the incident wave intensity grows exponentially (the dotted line on fig. 2), the light is neither transmitted nor reflected (the solid curve on fig. 2). That is, the layer looks perfectly absorbing despite the fact that it lacks the actual absorption capacity. However, when the exponential growth of the incident wave amplitude comes to a halt (at t = 0), the energy locked in the layer is released.
"Our theoretical findings appear to be rather counterintuitive. Up until we started our research, we couldn't even imagine that it would be possible to 'pull off such a trick' with a transparent structure," says Denis Baranov, a doctoral student at MIPT and one of the authors of the study. "However, it was the mathematics that led us to the effect. Who knows, electrodynamics may well harbor other fascinating phenomena."
The results of the study not only broaden our general understanding of how light behaves when it interacts with common transparent materials, but also have a wide range of practical applications. To give an example, the accumulation of light in a transparent material may help design optical memory devices that would store optical information without any losses and release it when needed.
Ilyana Zolotareva | EurekAlert!
Convenient location of a near-threshold proton-emitting resonance in 11B
29.05.2020 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences
A special elemental magic
28.05.2020 | Kyoto University
In living cells, enzymes drive biochemical metabolic processes enabling reactions to take place efficiently. It is this very ability which allows them to be used as catalysts in biotechnology, for example to create chemical products such as pharmaceutics. Researchers now identified an enzyme that, when illuminated with blue light, becomes catalytically active and initiates a reaction that was previously unknown in enzymatics. The study was published in "Nature Communications".
Enzymes: they are the central drivers for biochemical metabolic processes in every living cell, enabling reactions to take place efficiently. It is this very...
Early detection of tumors is extremely important in treating cancer. A new technique developed by researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from normal tissue. The work is published May 25 in the journal Nature Nanotechnology.
researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from...
Microelectronics as a key technology enables numerous innovations in the field of intelligent medical technology. The Fraunhofer Institute for Biomedical Engineering IBMT coordinates the BMBF cooperative project "I-call" realizing the first electronic system for ultrasound-based, safe and interference-resistant data transmission between implants in the human body.
When microelectronic systems are used for medical applications, they have to meet high requirements in terms of biocompatibility, reliability, energy...
Thomas Heine, Professor of Theoretical Chemistry at TU Dresden, together with his team, first predicted a topological 2D polymer in 2019. Only one year later, an international team led by Italian researchers was able to synthesize these materials and experimentally prove their topological properties. For the renowned journal Nature Materials, this was the occasion to invite Thomas Heine to a News and Views article, which was published this week. Under the title "Making 2D Topological Polymers a reality" Prof. Heine describes how his theory became a reality.
Ultrathin materials are extremely interesting as building blocks for next generation nano electronic devices, as it is much easier to make circuits and other...
Scientists took a leukocyte as the blueprint and developed a microrobot that has the size, shape and moving capabilities of a white blood cell. Simulating a blood vessel in a laboratory setting, they succeeded in magnetically navigating the ball-shaped microroller through this dynamic and dense environment. The drug-delivery vehicle withstood the simulated blood flow, pushing the developments in targeted drug delivery a step further: inside the body, there is no better access route to all tissues and organs than the circulatory system. A robot that could actually travel through this finely woven web would revolutionize the minimally-invasive treatment of illnesses.
A team of scientists from the Max Planck Institute for Intelligent Systems (MPI-IS) in Stuttgart invented a tiny microrobot that resembles a white blood cell...
19.05.2020 | Event News
07.04.2020 | Event News
06.04.2020 | Event News
29.05.2020 | Life Sciences
29.05.2020 | Physics and Astronomy
29.05.2020 | Life Sciences