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Scientists create world's most efficient light-bulb

August 27, 2003

Scientists have successfully produced the most efficient light bulb ever - but on the microscopic scale. Researchers at Trinity College, Dublin have discovered a technique which significantly improves the output of light from quantum dots, and also allows their light to be focussed and manipulated easily. Their findings are published today in the Institute of Physics journal Semiconductor Science and Technology.

Dr Yuri Rakovich and Dr John Donegan from Trinity College, Dublin working with researchers at the universities of Hamburg and Munich, have successfully placed quantum dots (the most efficient light-bulb in the world) onto a tiny polymer sphere.

Scientists have known for some time that quantum dots (tiny particles made from certain semiconducting materials) have numerous applications as they are capable of producing light without wasting any energy as heat. They are the basic unit of quantum computers - computers around 10,000 times faster that the fastest computer currently in use. John Donegan's team have found that they can make quantum dots more efficient than ever. By embedding quantum dots on the surface of a microsphere they can enhance the output of light from these quantum dots by a factor of 20 and - because these structures are spherical - they allow the light emitted from the quantum dots to be focussed into a fine beam which can be moved around easily by the researcher.

The Trinity College team's work has been carried out entirely under the microscope. They took a polymer microsphere of about 5 microns in diameter (one twentieth the diameter of a human hair) and coated the surface with quantum dots made of cadmium telluride, a semiconductor similar to gallium nitride. Once the surface of the microsphere was fully coated in quantum dots, they observed the surface emitting light in different colours; in this case red and green.

Dr Donegan and his team have been trying to improve the efficiency of light emission from quantum dots so that they can create a beam of light as tightly focussed as possible. These beams have a large number of possible applications and are likely to be applied to all branches of quantum technology in the future (computing, mobile phones, energy production). Dr Donegan's team are particularly interested in the manipulation of single strands of DNA. They are able to produce beams of light thin enough to be capable of manipulating a single strand of DNA, stretching it and reading the genetic information. Devices which can do this with light have been dubbed "optical tweezers" but Donegan's group believe they can now create a beam of light much finer than ever before and one which can be manipulated much more easily than previously thought possible.

Dr Donegan said: "We hope that our microcavity will help in all possible applications of quantum dots but especially in our ability to manipulate physically single strands of DNA. It could have major uses in genetic analysis and in gene sequencing where the ability to handle DNA strands with increasing accuracy and dexterity is becoming ever more important".

Institute of Physics