The advent of ultra fast LED or to prevent hacking

Researchers at the Duke University developed the latest ultrafast light emitting diode (LED), breaking the fluorescent molecular emission speed record, is 1000 times the normal level, towards the realization of ultra fast LED and quantum cryptography is an important step. The study was published in the October 12th edition of the journal Nature photonics.

This year's Nobel prize in physics was awarded to the scientists who invented the blue light-emitting diodes in the early 1990s, which has promoted the development of a new generation of bright, energy-saving white fluorescent lamps and color LED screens. However, the slow speed of this huge research results in the switch is limited to its use as a source of communication. In a LED, the atoms are forced to emit about 10 million photons in the blink of an eye. The modern communication system, running faster than the speed of LED photons emitted nearly a thousand times. In order to realize the optical communication based on LED, the researchers must speed up the photon luminescence material.

In the new study, the University of engineers by adding a fluorescent molecule between the metal cube and the gold film, accelerate its photon emission rate reached an unprecedented level. McCann Mikkelsen, an assistant professor of electrical and computer engineering and physics at the University, said: "one of the goals of this study is to use ultra high speed LED. Although future devices may not use this exact method, it is essential for fundamental physics. "

Mikkelsen is an expert in the study of the interaction between electromagnetic fields and free electrons in metals. According to physicist organizational network reported on October 13th, in the experiment, his team made 75 silver cubes, and trapped inside the light, greatly increasing the intensity of light. When the fluorescent molecules are placed close to the light, the speed of the photons emitted by the molecules is enhanced by the "Purcell effect". They found that the fluorescent molecules placed between the gold film and the gap between the nano metal, their speed can be significantly improved.

To achieve the maximum effect, researchers need to adjust the resonant frequency of the gap to match the color of the molecular response. In the paper's co-author, the College of electrical and computer engineering professor David Smith James, director of B's help, using computer simulation to determine the gold film between the nano cubic and required gap size: there are only 20 atoms wide. The researchers said: "we can choose to have the appropriate size of the cube, so that the gap has a nanometer level of accuracy, thus a record increase of 1000 times the speed of fluorescence. "

Because the experiment uses a number of randomly arranged molecules, researchers believe that can do better. They plan to put individual fluorescent molecules in a single cube, so as to achieve a higher rate of emission of photons.

The researchers said: "if we can accurately set the molecule, it will not only be fast LED, there are many applications. Such as the manufacture of fast single photon source for quantum cryptography system, this technology will support secure communications, to avoid hacking. "

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