Semiconductor acoustic lasers (sasers) - a big noise from nanostructures

Semiconductor acoustic lasers (sasers) – a big noise from nanostructures Sound amplification by the stimulated emission of radiation (saser) is the acoustic analogue of the laser. Sasers would provide an intense source of coherent acoustic waves which may be used in acoustic spectroscopy and imaging. The two key elements of a saser are a medium having acoustic gain and a cavity to confine phonons and so provide acoustic feedback. In this talk I will describe THz saser devices in which both the gain and confinement are provided by multi-layered semiconductor nanostructures known as superlattices (SLs). I will explain how the particular electronic properties of SLs can give rise to phonon amplification (acoustic gain) due to a phonon-stimulated quantum cascade of electrons through the structure. I will also explain how SLs act like one-dimensional phononic crystals to confine phonons. Recent experimental results providing the evidence for saser action in the devices will be presented.