Sound amplification by stimulated emission of radiation was first experimentally demonstrated in the Gigahertz range in 2009. Announced in 2010, two independent groups came up with two different devices that produce coherent phonons at any frequency in the range megahertz to terahertz. One group from the University of Nottingham consisted of A.J. Kent and his colleagues R.P. Beardsley, A.V. Akimov, W. Maryam and M. Henini. The other group from the California Institute of Technology (Caltech) consisted of Ivan S. Grudinin, Hansuek Lee, O. Painter and Kerry J. Vahala from Caltech implemented a study on Phonon Laser Action in a tunable two-level system. The University of Nottingham device
Sound amplification by stimulated emission of radiation operates at about 440 GHz, while the Caltech device operates in the megahertz range. According to a member of the Nottingham group, 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. A significant result rises from the operating frequency of these devices. The differences between the two devices suggest that SASERs could be made to operate over a wide range of frequencies. Work on the SASER continues at the University of Nottingham, the "Lashkarev Institute of Semiconductor Physics" at