Focusing of high power ultrashort Gaussian pulses to thin targets

Delivery of the highest energy into the smallest spot on a target within the shortest duration has been always one of the main goal of laser matter interaction experiments. The spatial distribution of a high power ultrashort laser pulse often follows Gaussian or super-Gaussian profile. However, the size of the optics in the laser beam line including the focusing optics in the target chamber is always limited. So far, these aperture effects were considered only for achieving small beam size in the focal plane, that is, transversal to the beam propagation direction. Now we show that the size of the aperture has a great influence on the intensity distribution along the optical axis, that is, in the longitudinal direction.