Ultrafast acoustics first began to get serious research over 20 years ago at General Motors(1). The basic concept is that sub-picosecond optical pulses generate longitudinal acoustic pulses with frequencies of 100 GHz and up. As a thin metal film is hit with alaser pulse, it reacts with a “breathing movement”: it expands and then it contracts.
No big deal? This movement takes place within a few tens picosecond and when this metal is in contact with another substance, the “breathing movement” is conveyed as a distortion wave with an extension of several nanometers. Form and intensity can relative precisely be adjusted by varying the strength of the laser bombardment.
When the wave rolls over an atom, the atom is immediately moved by some pecometers, representing an extreme severe deflection. Therefore the distortion wave can be regarded as a mighty 'nano-earthquake', according to Bayer's new research.
The aim of the application is to physically understand the effects triggered by such an “earthquake” and to look for potential applications - that's why it's basic research.
The distortion causes the energy of electrons to change very fast: increased when the material is compressed, decreased when the material is expanded. That means that the emission of light from light-emitting-diodes and lasers can be modulated as fast as never before; something that may be interesting for optic telecommunications.
It could also open up new fields of quantum physics. With the distortion moving quantum structures could continuously be created or the interaction of light and matter could venture new frontiers. In systems consisting of many interacting particles, phase transitions can be forced which cause the collective behavior of the particles change due to the distortion wave.
(1) Bruce M. Clemens and Gary L. Eesley, 'Relationship between Interfacial Strain and the Elastic Response of Multilayer Metal Films', Phys. Rev. Lett. 61, 2356 - 2359 (1988) DOI: 10.1103/PhysRevLett.61.2356