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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The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
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