December 07, 2006

New sound physics: hypersound and acoustic lasers

Radically new and powerful things are being done with sound. Part of what I think is the growing trend of greater control of all information, light, energy, matter and magnetism. (ILEMM) Molecular nanotechnology and advanced metamaterials would be milestones in the control of matter which will also provide greater control of energy. Better material devices will also mean better capabilities to investigate and understand phenomena.

Hypersound, acoustic pulsation at 200 gigahertz frequencies, has been produced in the same kind of resonant multilayered semiconductor cavity as used in photonics.
They believe that a new field, nanophononics, has been inaugurated, and that the acoustical properties of semiconductor nanodevices will become more prominent.
THz sound might also participate in the development of powerful "acoustic lasers" or in novel forms of tomography for imaging the interior of opaque solids.

A new kind of Acoustic Laser, sound amplification by stimulated emission of raciation, or SASER, is the acoustic analog of a laser. Instead of a feedback-built potent wave of electromagnetic radiation, a saser would deliver a potent ultrasound wave.
In lasers the light buildup is maintained by a reflective optical cavity. In the U.K.-Ukraine saser, the acoustic buildup is maintained by an artful spacing of the lattice layer thicknesses in such a way that the layers act as an acoustic mirror.

Eventually the sound wave emerges from the device at a narrow angular range, as do laser pulses. The monoenergetic nature of the acoustic emission, however, has not yet been fully probed. The researchers believe their saser is the first to reach the terahertz frequency range while using also modest electrical power input.

Further reading:
More physics papers on hypersound

More physics papers on acoustic lasers

More physics papers on metamaterials