A SASER is the acoustic analogue of the laser. It is capable of producing highly coherent, concentrated beams of ultrasound, using methods very similar to those employed in the laser. First experimentally demonstrated in the Gigahertz range in 2009, [1] the SASER is being developed at the University of Nottingham, the Lashkarev Institute of Semiconductor Physics, and Caltech. The University of Nottingham device operates at about 440 GHz, while the Caltech device operates in the megahertz range. In an interview, a member of the Nottingham group, told physicsworld.com that "the two approaches are complementary and it should be possible to use one device or the other to create coherent phonons at any frequency in the megahertz to terahertz range." [2]
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A SASER operates on principles remarkably similar to those of a laser. A stack of thin semiconductor wafers are placed in a lattice within an acoustically reflective chamber. Upon the addition of electrons, short-wavelength (in the terahertz range) phonons are produced. Since the electrons are confined to the quantum wells existing within the lattice, the transmission of their energy depends upon the phonons they generate. As these phonons strike other layers in the lattice, they excite electrons, which produce further phonons, which go on to excite more electrons, and so on. Eventually, a very narrow beam of high-frequency ultrasound exits the device.
A second meaning of SASER is the thermoacoustic laser. This is a half-open pipe with a heat differential across a special porous material inserted in the pipe. Much like a light LASER, a thermoacoustic SASER has a high-Q cavity and uses a gain medium to amplify coherent waves. See thermoacoustic heat engine.
Apart from allowing the investigation of terahertz-frequency ultrasound, the SASER is also likely to find myriad uses in optoelectronics, as a method of signal modulation and/or transmission.[3]