Comment on "Generation of 10(11) contrast 50 TW laser pulses".
We argue for a different physical interpretation of the results given in the recent Letter by Chvykov et al. [Opt. Lett.31, 1456 (2006)] in which a double nonlinear crystal scheme for cross-polarized wave generation is analyzed. We discuss the most important factors that explain the origin of the two-crystal scheme's increased efficiency, namely, the Kerr lensing effect and a Gouy phase shift. The position and orientation of the second crystal relative to the first one are unambiguously defined; related effects are illustrated by already published works on the subject.
Albert
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Laboratoire d'Optique Appliquée, ENSTA-Ecole Polytechnique-CNRS, 91761 Palaíseau Cedex, France. oliver.albert@ensta.fr
Jullien
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A
Etchepare
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J
Kourtev
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Minkovski
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Saltiel
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