Collective behavior and disorder-induced resonator of random lasers

The localization caused by multiple scattering of lightwaves provides a mode for random laser action. It is shown that once the gain surpasses a certain threshold, photons are driven to localized modes, which greatly suppresses the energy loss and leads to laser emission. Concurrent with the localization of the random laser, unique collective behaviors of the localized modes appear, as distinguished from the other modes, which reveals the "invisible" microcavities of random lasers. (c) 2005 American Institute of Physics.