Birth of the Saser
In this paper we describe a new type of acoustic laser device, or saser
(for sound amplification by stimulated emission of radiation), based on
a semiconductor nanostructure pumped by a light beam. Such a device has
the potential to transform the field of acoustics just like the laser
has transformed optics in the half-century since its invention. We
present experimental evidence for the device working as a saser, which
is a pumping power threshold above which the sound emission increases in
intensity rapidly and becomes more directional. These properties are
analogous to those of the light emission from semiconductor lasers
common in optical disc readers etc. The experimental evidence is backed
up by theoretical calculations which predict that saser oscillation is
indeed possible in the device. This is not the first saser device to be
demonstrated, we previously demonstrated an electrically pumped device.
However, we believe this is the first to emit transverse-polarized, or
shear, sound waves in the terahertz frequency range. Such sound waves
have applications in imaging and testing of nanostructures and for the
control of the electrical, optical and magnetic properties of
nanodevices.
