Semiconductor lasers generate a significant amount of heat during operation, which causes a number of undesirable effects including increasing the current necessary for a given emission intensity and shorter device lifetime. Especially quantum cascade lasers (QCL) are sensitive to temperature, which results in a reduction in light emission or a cessation of laser operation. <br><br> <strong>Technology</strong><br> The QCL consists of an active zone which comprises a cascade structure and an insulating heat-dissipating zone which is laterally adjoined to the active zone. The active zone, which generates heat, is made from a semiconductor material with high crystalline order. The insulating heat-dissipating zone is made from an electrically insulating, heat conducting material which is identical to the semiconductor material of the active zone. The electrically insulating property of the heat-dissipating material is based on a reduced level of crystalline order compared to the semiconductor material of the active zone. The crystal defects result from growth on an underlying amorphous film. The pre-patterned substrate is made of a robust amorphous material and is able to withstand temperatures of growth and processing up to ~ 600 °C. The active regions are defined prior to epitaxy so that the processing is largely finished (except for metallization) when the structure emerges from the epitaxy reactor. <br><br>
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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...
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