The focal spot was found to be very close to the one expected for a diffraction-limited beam.
As a drawback, this technique introduces diffraction by the mirror central edge.
Limpouch et al. harmonics on the rear side of the spherical target is comparable to that on the front side due to laser diffraction.
It shows reshaping of argon ions with diffraction pattern and broken chains.
It is a major dominant term that although initially small, competes with the diffraction term to determine the overall evolution of beam width.
Therefore, for a compensated optical design, both the diffraction of the grating and the dominant aberrations have to be corrected.
This reference wave is generated by the diffraction of a very small pinhole.
The laser beam was diffraction limited, the focal spot diameter was found to be 2 mm, in agreement with the expectations.
