Professor Konstantin Arutyunov of the Moscow Institute of Electronics and Mathematics HSE Tikhonov (MIEM HSE), in collaboration with Chinese researchers, has developed a mechanical resonator based on graphene, in which a coherent emission of quanta of sound energy, or phonons , was induced. Such devices, called phonon lasers, have a wide potential for application in information processing, as well as in classical and quantum detection of materials. The study is published in the journal Optical Express.
By analogy with photons, quanta of the electromagnetic spectrum, there are also particles of sound energy, phonons. In fact, they are artificially introduced objects in physics – quasi-particles, which correspond to the vibrations of the crystal lattice of matter.
Some substances, when irradiated, emit photons of the same wavelength, phase and polarization. This process, called stimulated emission, was predicted by Albert Einstein over a century ago and is the basis of the device we all know: the laser. The first lasers were built about sixty years ago and they have firmly established themselves in our lives in various fields.
A similar process, involving the emission of “identical” phonons, underlies a device called, by analogy, a phonon laser or saser. In fact, it was predicted at the same time as lasers, but only a few experimental achievements have been developed over a long period of time, and none of them have been widely used in industry.
Magnesium ions, semiconductors, composite microcavity systems, electromechanical resonators, nanoparticles and many other substances and systems have been used as active carriers for phonon lasers over the past decade. Unlike previous studies, this study used graphene to create coherent acoustic excitations. Due to the unique properties of graphene, such resonators can potentially be widely used.
The graphene resonator was produced by microlithography: a photosensitive polymer film is deposited on a silicon substrate. Using ultraviolet light, a certain structure is “drawn” on the substrate, which then allows the formation of a repeating system of micro-cavities by means of plasma treatment. The treated substrate is covered with a layer of graphene, and this system of “drums” behaves like a resonator, that is to say it amplifies the external vibrations if they are generated with a certain frequency.
If such a “drum” is irradiated with laser light at a specific wavelength, the photons are repeatedly reflected between the silicon support and the graphene, thus forming optical cavities where mechanical vibrations of the appropriate frequency are reflected. produced.
“As an experiment, we looked at a nanostructure, which is a fixed membrane made up of a monatomic layer of carbon or graphene. Vibrations of atoms, or phonons, were activated there by exposure to external optical radiation, ”explains Konstantin Arutyunov. “Research is expected to continue, as it has considerable interest both in the physics of ultra-small objects and has the potential to create a new generation of quantum optomechanical sensors and transducers.”
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