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We discuss the spatial and spectral intensity distribution of emission in optical gain media under stripe excitation in the case where the intensity reaches saturation level. It is found that modes propagating along the stripe in different directions are spatially separated if they affect each other due to saturation. The investigation includes the effects of wavelength-dependent inhomogenities, such as localized losses and reflective perturbations. Even relatively small distortions of this kind are found to cause considerable spatial and spectral redistribution of the intensity compared to an ideal disorder-free medium. Our results indicate that a simple ansatz may describe some mechanisms that lead to the formation of random laser action that is commonly observed in high gain media, such as organic semiconductors. Furthermore, consequential difficulties of gain measurements in such media using stripe excitation experiments are highlighted.
Date of Publication: Sept. 2012