Scattering strength dependence of terahertz random lasers

Random lasing operation requires an active region, a gain medium that supports multiple scattering, and, especially for integrated optoelectronic devices, a nonresonant outcoupling mechanism over a continuous spectrum. For broadband operation, the resonator geometry must provide frequency nonselective, strong feedback over a large bandwidth. The feedback mechanism by multiple scattering in terahertz semiconductor random lasers and the bandwidth of such cavities are presented and discussed. We demonstrate the influence of shape and scattering strength of the scatterers on the lasing process and determine the bandwidth of such resonator structures. We use passive resonator structures to prove that the feedback as well as the outcoupling is frequency independent over a large bandwidth.