Most lasers use an optical cavity for their operation. In the simplest case such a cavity can be made is using to plane mirrors and the active material in the middle. The active material gives optical amplification and the mirrors give the optical feedback. Only a small amount of light leaves the cavity, the most travels back trough the active material and gets amplified again.
In a random laser these mirrors are replaced by scatterers, which act as a very bad mirror, which only gives small feedback and has high losses. But if the optical amplification between the scattering processes is high enough to overcome this losses. Lasing starts without mirrors.
Our research in random lasing concentrates on the investigation of wide band gap semiconductor multi quantum well structures, based on zinc oxide. These samples provide the necessary optical amplification for laser action with only small optical feedback by scattering. In the picture such a multi quantum well sample based on Zinc Oxide and Zinc Cadmium Oxide is shown while lasing. In the growth process small holes appear in the layers, and these scatter the light and provide the optical feedback.
letzte Änderung: 21.09.2015 id