Researchers at the Massachusetts Institute of Technology (MIT; US) discovered a phenomenon in a sheet of graphene analogical to a jet airplane traveling faster than the sound waves, which creates a “sonic boom”: Here, a flow of electric current can exceed the speed of slowed-down light and produces a kind of “optical boom” — an intense, focused beam of light.
Creating the optical boom
“The key to this process is the ability of novel materials like graphene and other 2D materials to trap light and guide it while slowing it down by more than two orders of magnitude,” explains Ido Kaminer, postdoctoral fellow in the MIT Department of Physics and assistant professor of electrical engineering at the Israel Institute of Technology, Technion. This slows the speed of light — the phase velocity — inside such materials to the speed of the charge carriers. “Matching the velocities enables super strong light-matter interactions, and we are still discovering the amazing implications of such super strong interactions since it goes beyond our intuition for how light interacts with matter,” says the researcher.
The effect of this “optical boom” is the result of light moving slower than the charge carrier that emits it. Kaminer notes that the first observation of an “optical boom” is actually a few decades old and was achieved in 1934 by Pavel Äerenkov, who later was awarded the Nobel Prize for this discovery. “However, in the 80+ years that passed since then, the ‘optical boom effect,’ or as we teach it to student, the ‘Äerenkov effect,’ was mostly irrelevant to modern technology.” Why? The charge particles necessary for the emission of light had to go to relativistic (very high) speeds to compete with the speed of light — something the expert says we cannot achieve in micro- and nanodevices. “It is only now, thanks to modern materials like graphene, that we can slow down the phase velocity of light enough to bring it closer to the speed of the charge carriers in small devices.”
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Source: Novus Light Technologies Today