A saser (sound amplification by stimulated emission of radiation) is a device that emits concentrated, highly-focused sound waves.
The saser is the sonic equivalent of the laser and is often referred to as a sound laser or acoustic laser. Sasers beam concentrated sound waves in the terahertz (THz) range. While still mostly a curiosity in the scientific world, sasers offer a number of potential practical uses.
Sasers could read or relay digital information, as many lasers do. Sasers could also enable super-accurate sonograms able to, for example, detect defects in electronics on the microscopic nanometer level. Medical imaging and biometrics are among many other possible areas of application. At low frequencies, sasers can produce sound at a distance; at high frequencies, they can heat a distant target.
A saser consists of a pump to add energy (typically in the form of intense light) to the system of a 50-layer super-lattice that alternates sheets of gallium arsenide and aluminum arsenide, each merely a couple of atoms thick. The super-lattice is held in a structure within which the layers are excited, bouncing particles and refocusing them until they reach sufficient energy to be released as photons, in a focused stream of associated particles that vibrate at the same frequency.