Chaotic Lasers Tamed

"Classical" laser shine has become part of everyday life. There is a laser in every CD player, lecturers end to their slides with laser pointers and surgeons carry absent medical operations with laser beams. Nevertheless there are numerous unusual kinds of laser bright that are still largely unexplored, one of them being Diffusive Random Lasers (DRLs). The quantum physicist Hakan Türeci from the Quantum Photonics Party of the ETH Zurich Institute for Quantum Electronics says "The basic belief behind DRLs is amazingly simple." He and colleagues from Yale University and Vienna University of Technology describe latest knowledge about the physics of DRLs in a paper published in Science. They have also developed a recent formula with which lasers can be re-computed from first principles. This mode they have created a framework to understand the properties and development of such complex, exotic lasers. Lasers without mirrors A normal laser beam is generated in a cavity between
two mirrors. The brilliance flashes to and fro, passing through an amplifying medium on the way. An external "pump" supplies energy. One of the mirrors is semi-transparent and allows the laser beam to emerge. It is relevant that the flash inside the cavity is not scattered, for example by impurities, as this would reduce the influence of the laser beam. This kind of laser beam is directional and has a particular frequency, i.e. colour. On the other labourer the development of DRLs is still in its infancy, although the principle was already postulated by a Russian researcher in 1968. The advantage of a DRL: no expensive polished mirrors are needed to generate the laser light. The amplifier medium can be a dye solution containing nano-particles such as titanium dioxide. These particles are randomly distributed in the solution, which is excited by a glowing source and "pumped" with energy from outside. Random spectrum The input luminosity is scattered randomly on the nano
-particles, bouncing from one particle to another and being amplified at the same time. This does not require a cavity like a conventional laser. With optimum pump power, i.e. the supply of external energy in the form of blaze or electric current, laser flare finally emerges from the medium. However, the hot-spots with the maximum illumination intensity are unpredictable, nevertheless in most cases they are in a ring-shaped pattern at the edge of the amplifier medium. A random laser of this kind also does not have a sharply defined frequency. Countless frequencies that can mutually cancel each other gone occur in a DRL system, i.e. they operate a kind of frequency Darwinism. In the end only the "strongest" frequencies remain. "However, the intensity of these winners is also unstable and fluctuates from one pulse to the next, " says Türeci. The researchers have also designed a contemporary mathematical model in their paper, an ab initio laser theory, a fundamental st
arting speck that allows them to predict the force of lasers. The physicist explains: "We have a completely fresh formula with which we can calculate all the physical properties." He says these can be used to develop novel laser methods, for example, and will become primary in the future. Full text: http://computerandtechnologies.com/technology/news_2008-08-08-12-30-03-948.html