But this effect can also be reversed. When the frequency of the laser beam makes the irradiated material just not absorbing its light and slightly more energy (of the photons, as physicists call the light particles) is needed for that, this photons “take” this missing energy from the oscillation energy of the material’s atoms.
Such oscillation energy (“phonons”) is equivalent to the vibration of atoms which is also called temperature and which is slightly reduced by this: the material is cooled down. A team of scientists from Technische Universität Dortmund and Ruhr-Universität Bochum has just carried out the first detailed experimental study regarding this process (known as “photoluminescence up-conversion”) in semiconductor nanostructures. Based on this, the development of a vibration-free cooling of semiconductors might be possible.
The scientist especially determined the optimal laser wave-length as a function of temperature. They found out that the cooling efficiency of any laser beam increases with the temperature, analog to conventional cooling systems.
The temperature in the material, which has to be slightly lower than the photon energy, is adjusted when the gallium-arsenide layers are created, which are embedded in aluminum-gallium-arsenide layers. The thickness of the gallium-arsenide layer, usually a few dozens atom layers, determines this energy.
This so-called “quantum wells”, which can be created with the precision of one atom layer can also be applied to the latest semiconductor-laser generation. This technology can therefore be used to produce the sending laser as well as the cooling material.
The study has been carried out at the Chair for Experimental Physics III, Technische Universität Dortmund, by Dr. Soheyla Eshlaghi, Wieland Worthoff and Prof. Dr. Dieter Suter as well as Prof. Dr. Andreas D. Wieck from the Chair for Applied Solid-State Physics, Ruhr-Universität Bochum. It is published in the current edition of the Physical Review, one of the oldest and most distinguished professional journals in physics.
Ole Luennemann | alfa
Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State
What do Netflix, Google and planetary systems have in common?
02.12.2016 | University of Toronto
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...
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...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy