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SHARP Informe resumido

Project ID: HPRI-CT-2001-50037
Financiado con arreglo a: FP5-HUMAN POTENTIAL
País: France

double CPA with non linear induced birefringence rotation

Double CPA with non linear induced birefringence rotation:
The principle of the double CPA concept is to build a first CPA laser system in order to obtain femtoseconde pulses at a millijoule level. Those pulses are filtered thanks to a nonlinear filter in order to obtain pulses of a few hundred of microjoules with a high contrast. The laser beam is then amplified again in a second CPA laser chain.

The nonlinear filter presented here is based on nonlinear induced birefringence in air. In this experiment, the laser is focus in the air. At the focal point, the intensity of the femtosecond part of the laser pulse is high enough to make some nonlinear effects, which turn the polarisation of the laser beam.

The intensity of the ASE part or of the satellite pulses does not generate such effects. Thanks to a polarizer, it is then possible to discriminate the femtosecond pulse from the ASE background. The pulse cleaning depends of the pulse energy, the beam diameter at the focal point, the chirp of the pulse before the filter.

The best results we obtained were 125 µJ, 55fs pulses with an improvement of the contrast by 3 orders of magnitude. Thanks to the possibility to make a spatial filtering during the process, the spatial quality of the laser beam is good. Those results are very sensitives to the experimental parameters which have to be carefully adjusted.

Reported by

laboratoire d'optique appliquee
chemin de la huniere, batterie de l'yvette
91761 Palaiseau cedex
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