Suppression for the Low spatial frequency Rings and Ripples of Laser Near field Intensity Distribution in the Spatial Filter Used in ICF Laser DriveSupported by the key project of the National Science Foundation, National Hi Tech Foundation.

We report a new technique to suppress the low spatial frequency rings and ripples (LSFRs) of laser near field intensity distribution in the spatial filter (SF) used in ICF laser drivers. This technique employs a spatial filter with Gaussian transmission, instead of the hard edged pinhole, at the confocal plane of a Newtonian telescope. The resulting beam has a super Gaussian transverse intensity profile without the LSFRs that certainly appear when a hard pinhole was used as a filter in the conventional technique.