Abstract

The damage threshold of diffraction gratings is one of the main constraints of grating compressors: indeed, in PW facilities, meter-scale gratings should be used, to stay within the damage-threshold. Nevertheless, since the fabrication process for such gratings limits the maximum size of a monolithic grating to less than one meter, alternative approaches have been studied. In the solution chosen for the CEA Petawatt project (PETAL PETawatt Aquitaine Laser), the compressor is made of 4 small independent compressors [1], The amplified beam is first split into 4 beams, which are recombined after compression. These beamlets have to be phased to act as a monolithic beam. In a previous study [2], we demonstrated that quadri-wave lateral shearing was an appropriate method to determine the phase difference between two sub-apertures of a segmented laser beam. Its main advantage is that the measurement is very simple, since it analyzes the wave front of the recombined laser beam in the near field.

© 2007 IEEE