Plasma spatial filter

A plasma spatial filter developed for a laser system is described. The target is placed at the lens focal position, in place of a pinhole. The laser beam focused on the target generates a small plasma spot which acts as an active mirror, reflecting a portion of the laser beam back along the incident path. The plasma-reflected beam when amplified produces a high-energy beam for irradiating pellets. The filtered beam differs from the input beam in: its smooth time-integrated spatial intensity profile, and broadened bandwidth. The number of conventional pinhole spatial filters required to retard the growth of beam filaments can be lowered by using the plasma spatial filter in a high-power laser system. Self-focusing and damage it might induce in optical components are much less likely with this filter.