Spatial quality improvement of a Ti:Sapphire laser beam by modal filtering
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We present a study on the improvement of the spatial quality of a laser beam, called modal filtering, suitable to high-energy lasers. The method is theoretically compared with the classical pinhole filtering technique in the case of an astigmatic Gaussian beam, illustrating, in this particular case, its efficiency for filtering low spatial frequencies. Experimental study of the modal filtering of a temporally chirped beam from a Ti:Sapphire chirped-pulse-amplification system is presented. Beam profile, wavefront and pulse duration after compression were measured, showing a dramatic improvement of beam quality and no modifications of the temporal distribution. High-order harmonic generation in a rare gas, a highly nonlinear process which is phase-matching dependent, was used to test the effect of the filter and showed a clear enhancement of the generation.
KeywordsFocal Plane Gaussian Beam Hollow Fiber Astigmatism High Spatial Frequency
This work has been sustained by ANR I-NanoX project and FEMTO-X-MAG. We thank Giovanni De Ninno and Romain Bachelard for constructive discussions and are also grateful to the Egide agency, the Triangle de la Physique network and the COST European network for their financial support in the framework of, respectively, the XUV-FISCH project, the XUV-PhLAGH project and the MP1203 action.
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