Improved pinhole spatial filter

摘要

Lasers generate phase aberrated light that can damage laser glass, frequency conversion crystals, lenses, and mirror coatings and can also reduce extractable energy and power. Spatial pinhole filters can partly eliminate such ''hot spots.'' Problems are that the pinhole closes during the laser pulse and has to be made too large initially. Debris from the pinhole can coat or damage spatial filter lenses. This paper presents a novel design for a more robust pinhole filter. Phase distorted (hot spot) light refracts at grazing incidence by plasma on the wall of a funnel shaped filter resulting in less absorption and debris. Refracted light absorbs at low intensities on the vacuum wall. We present 2D hydrodynamic computer simulations and compare the two types of filters with experiment.