Researchers at Duke University in the United States have recently developed ultra-fast light-emitting diodes (LEDs) that break the speed record of fluorescent molecules emitting photons, 1,000 times that of the ordinary class, and have taken an important step towards ultrafast LED and quantum cryptography. The results of the study were published on the online version of Nature Photonics on October 12.
This year's Nobel Prize in physics was awarded to scientists who invented blue light-emitting diodes in the early 1990s, as the invention 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 result in switching limits its use as a light source-based communication. In an LED, a blinking kung fu atom was forced to emit about 10 million photons. In modern communication systems, the operating speed is nearly a thousand times faster than the speed at which LEDs emit photons. In order to achieve LED-based optical communication, researchers must speed up photonic luminescent materials.
In the new study, the university's engineers accelerated the photon emission rate to an unprecedented level by adding fluorescent molecules between the metal nanocubes and the gold film. McCann Mickelson, assistant professor of electrical and computer engineering and physics at the University, said: "One of the target applications for this research is ultra-high-speed LEDs. Although future equipment may not use this exact method, it is essential for basic physics. important."
Mickelson is an expert in the interaction between electromagnetic fields and free electrons in metals. According to the report of the Physicist Organization Network on October 13, in the experiment, his team created 75 silver nanocubes and trapped the light in it, which greatly increased the light intensity. When fluorescent molecules are placed near dense light, the speed at which the molecules emit photons is enhanced by the "Pursel effect". They found that placing fluorescent molecules between the gold film and the gap between nano-metals can increase their speed significantly.
To achieve the maximum effect, researchers need to adjust the resonant frequency of the gap to match the color of the molecule's response. With the help of the co-author of this paper, Professor David Smith, the professor of electrical and computer engineering at the university, and director James B, computer simulations were used to precisely determine the required gap size between nanocubes and gold films: there were only 20 Atomic width. The researchers said: "We can choose the right size of the cube, so that the gap has a nanometer accuracy, thus a record increase in fluorescence speed of 1000 times."
Because the experiment uses many randomly arranged molecules, the researchers believe that they can do better. They plan to place individual fluorescent molecules precisely in a single nanocube, enabling the fluorescent molecules to emit photons at higher rates.
The researchers said: “If we can set the molecules accurately, they will not only be fast LEDs, but also have many applications. For example, to create fast single photon sources for quantum cryptography, this technology will support secure communication and avoid hacking. "(Hua Ling)
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