Number 271 (Story #2), May 16, 1996 by Phillip F. Schewe and Ben Stein THE ACOUSTIC ANALOG OF A LASER is being developed by Jean-Yves Prieur at the University of Paris-South (Physica B, vol. 219/220, p. 235). The active medium in this case is a piece of pure silica at a temperature of 0.5 K. An initial sound pulse "pumps" the sample by depositing acoustic energy at absorbing centers throughout the silica. A second sound pulse stimulates the absorbing centers ro reradiate phonons, which serve to amplify the second pulse. Unfortunately, the amount of amplifications is still low because the pump pulse remains in the system, where it undermines the stimulation process. The researchers believe that eventually acoustic lasers will be used as sensitive particle detectors. (New Scientist, 27 April 1996.)