Regensburg 2010 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 57: Focussed Session: ZnO-based Semiconductors

HL 57.5: Vortrag

Donnerstag, 25. März 2010, 15:15–15:30, H17

Excitation dynamics in ZnO random lasers — •Janos Sartor, Felix Eilers, Jonas Conradt, Cornelius Thiele, Claus Klings-hirn, and Heinz Kalt — Angewandte Physik, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany

Random lasing is a phenomenon that appears in strongly scattering systems providing optical gain. In our work we investigate the spatial extent of laser modes in ZnO powders with grain sizes of the order of the emission wavelength. It has been shown that this material system is well suited for research on random lasing since the ZnO nanoparticles provide sufficient gain and scattering at the same time. Usually the emission of a random laser fluctuates too much to distinguish the vast amount of lasing modes. By reducing the volume of our random lasing medium to micro-sized structures we were able to reduce the number of modes as well, until only a few distinguishable modes remained. We observe the coexistence of strongly localized and extended modes and thus solve a longstanding discussion in current theoretical work. The mode extent is directly linked to the strength of the optical gain.