Spatial beam self-cleaning in second-harmonic generation
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Krupa K., Fona R., Tonello A., Labruyère A., Shalaby B. M., Wabnitz S., Baronio F., Aceves A. B., Millot G., Couderc V.
ISSN: 2045-2322
We experimentally demonstrate the spatial self-cleaning of a highly multimode optical beam, in the process of second-harmonic generation in a quadratic nonlinear potassium titanyl phosphate crystal. As the beam energy grows larger, the output beam from the crystal evolves from a highly speckled intensity pattern into a single, bell-shaped spot, sitting on a low energy background. We demonstrate that quadratic beam cleanup is accompanied by significant self-focusing of the fundamental beam, for both positive and negative signs of the linear phase mismatch close to the phase-matching condition.