Now physicists need not fully control the growth of laser crystals, because the crystals grow themselves. Professor Nikolay Ledentsov and his team at the Ioffe Physico-Technical Institute have learned how to provide special conditions in which crystals can grow defectless.
Growing crystals with enhanced characteristics is possible on the basis of the effect of quantum dots. A quantum dot is a tiny islet of one material lost in the monocrystal of the other material. For a long time the scientists thought that it is impossible to grow a perfect crystal with "raisins" of other material inside. However, researchers at the laboratory of Zhores Alferov have proved that the grown crystals are good for lasers.
Technology of growing is very important. Usually heterostructural materials, e.g. consisted of gallium arsenid and indium arsenid, are made by placing a layer by layer. Now the researchers can do without this laborious procedure. According to professor Ledentsov it is enough to choose right conditions: temperature, deposition rates, ratios between atom flows etc. In this case a perfect material will grow and the "raisins" will arrange in a strict order. Having known regularities of the growth, it is possible to make beads, chains, "saucers", small or big islands of quantum dots etc.
Tatiana Pitchugina | Informnauka
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Controlling electronic current is essential to modern electronics, as data and signals are transferred by streams of electrons which are controlled at high speed. Demands on transmission speeds are also increasing as technology develops. Scientists from the Chair of Laser Physics and the Chair of Applied Physics at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have succeeded in switching on a current with a desired direction in graphene using a single laser pulse within a femtosecond ¬¬ – a femtosecond corresponds to the millionth part of a billionth of a second. This is more than a thousand times faster compared to the most efficient transistors today.
Graphene is up to the job
At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.
Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
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