Materials such as milk, paper, white paint and tissue are opaque because they scatter light, not because they absorb it. But no matter how great the scattering, light is always able to get through the material in question.
At least, according to the theory. Researchers Ivo Vellekoop and Allard Mosk of the University of Twente have now confirmed this with experiments. By shaping the waveform of light, they have succeeded in finding the predicted ‘open channels’ in material along which the light is able to move. The results will soon be published in Physical Review Letters and are already available on the authoritative websites: ScienceNOW and Physics Today.
In materials that have a disordered structure, incident light is scattered in every direction possible. In an opaque layer, so much scattering takes place that barely any light comes out ‘at the back’. However, even a material that causes a great deal of light scattering has channels along which light can propagate. This is only possible if the light meets strict preconditions so that the scattered light waves can reinforce one another on the way to the exit.
Always an open channel
By manipulating the waveform of light, Vellekoop and Mosk have succeeded in finding these open channels. They used an opaque layer of the white pigment, zinc oxide, which was in use by painters such as Van Gogh. Only a small part of the original laser light that falls on the zinc oxide, as a plane wave, is allowed through. As every painter knows, the thicker the paint coating, the less light it will let through. By using information about the light transmitted to programme the laser, the researchers shaped the waveform to the optimum form to get it to pass through the open channels.
To this end, parts of the incident wave were slowed down to allow the scattered light to interfere in precisely the right manner with other parts of the same wave. In this way, Vellekoop and Mosk increased the amount of light allowed through by no less than 44 percent. As theoreticians had predicted, open channels can always be found and transmission through them is, furthermore, independent of the thickness of the material concerned.
The results are highly remarkable: although the theoretical existence of open channels was acknowledged, so far manipulating the light such that the channels in materials could actually be found has been too complex. As a result of better light conductivity in opaque materials, it may in the future be easier to look into materials that have so far not divulged their secrets: for example in medical imaging technology. There is a significant parallel with the conductivity of electrons in extremely thin wires, such as those on semi-conductor chips. Electrons, which according to quantum mechanics behave as waves, move through these same open channels.
It is also conceivable that this research will yield more information about waveforms other than light, such as radio waves for mobile communication: can the range be improved by adjusting the waveform?
This research was carried out in the Complex Photonic Systems group of the University of Twente’s MESA+ Institute for Nanotechnology. It is financed by the Foundation for Fundamental Research on Matter (FOM) and by a Vidi grant from the Netherlands Organization for Scientific Research (NWO).
Wiebe van der Veen | alfa
UNH scientists help provide first-ever views of elusive energy explosion
16.11.2018 | University of New Hampshire
NASA keeps watch over space explosions
16.11.2018 | NASA/Goddard Space Flight Center
Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.
Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure
Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...
09.11.2018 | Event News
06.11.2018 | Event News
23.10.2018 | Event News
16.11.2018 | Health and Medicine
16.11.2018 | Life Sciences
16.11.2018 | Life Sciences