Random laser spectrum responds to temperature
When properly manipulated by laser pulses, Bose-Einstein condensates (BECs) made of magnetically trapped clouds of atoms cooled to near absolute zero can slow and even stop light (see Laser Focus World, April 1999, p. 16). Such atomic clouds, however, are difficult to create and maintain.
By combining liquid-crystal technology with light diffusion in random systems, researchers at the European Laboratory for Non-Linear Spectroscopy (LENS; Florence, Italy) have created a random laser source that changes its color spectrum in response to changes in temperature. With a diffusive ground-glass powder as the scattering medium and a laser dye to provide gain, random lasers operate by multiple random-scattering events between disordered particles rather than the mirrored lasing cavity in traditional lasers.