The angular emission pattern of a random laser is typically very irregularand difficult to tune. Here we show by detailed numerical calculations that onecan overcome the lack of control over this emission pattern by actively shapingthe spatial pump distribution. We demonstrate, in particular, how to obtaincustomized pump profiles to achieve highly directional emission. Going beyondthe regime of strongly scattering media where localized modes with a givendirectionality can simply be selected by the pump, we present anoptimization-based approach which shapes extended lasing modes in the weaklyscattering regime according to any predetermined emission pattern.
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