Shocking light from crystals

Using a projectile or a laser blast to send a shudder through the regimented planes of crystals can incite the emission of coherent, laserlike light in hard-to-access terahertz frequencies, according to a theoretical study by physicists at Lawrence Livermore National Laboratory and MIT (Phys. Rev. Lett. 2006, 96, 013904). If confirmed in tests now in the planning stages, the discovery will add to an extremely short list of known ways for generating coherent light. "Lasers are inherently quantum beasts, but this is a purely classical mechanism for generating the radiation," says lead researcher Evan J. Reed, who recently moved from MIT to LLNL. In the team's simulations, a shock front plows through a crystal, transiently displacing crystal plane after crystal plane. As the planes relax, their constituent atoms emit terahertz radiation, a portion of which should be coherent (shown, in a band at 22 THz) because of the periodicity of the moving crystal planes.