Periodically-pumped organic microlasers

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In this project, we propose the experimental and theoretical investigation of localised quasimodes and the formation of supermodes in planar microcavities having an organic active medium. To this end, the planar organic microcavities shall be excited in a spatially inhomogeneous fashion, to induce a spatial modulation of the distributions of gain and absorption within the organic cavity layer. A major effort will be put on the experiments which use an interference patterns for periodic optical pumping of organic microcavities. In this case, our preliminar results show that the coherence may extend in-plane over the entire pump pattern and is not restricted anymore by the mode volume of the microcavity, which is mutual to the planar structures and is typically very small. This observation is of crucial importance for the future applications which will involve a periodic electrical pumping of organic microcavity lasers. First of all it shows, that the lasing volume may be extended due to the in-plane propagation of the coherence, which might lead to much higher emission powers of a single-mode organic laser. Secondly, since discretization of the in-plane vector leads to an oblique emission with respect to the normal of mirrors, so that the propagation vector for the coherent light does not concide anymore with the electric current flow. This decoupling of the optical flow from the electrical excitation reduces the influence of the contacts and currents, which are parasitic and degrade laser performance and characteristics.The aim of the project is to obtain a basic understanding of spatially coherent processes in a planar microcavity, and to develop the ability to manipulate these processes. In contrast to the direct incorporation of different structures into the cavity layer or even physical structuring of this layer, the use of the periodic optical pumping offers an incomparable flexibility in the experiments. It allows both to optimize these structures for the future incorporation of e.g. metal contacts and also to obtain a deeper understanding of the fundamental physics of microcavity lasers.