9 S ep 1 99 8 Concentrator of laser energy for thin vapour cloud production near a surface

A novel scheme is presented for production of a thin (< 1 mm) uniform vapor layer over a large surface area (> 100 cm 2) by pulsed laser ablation of a solid surface. Instead of dispersing the laser energy uniformly over the surface, a modified Fabry-Perot interferometer is employed to concentrate the laser energy in very narrow closely-spaced concentric rings. This approach may be optimized to minimum total laser energy for the desired vapor density. Furthermore, since the vapor is produced from a small fraction of the total surface area, the local ablation depth is large, which minimized the fraction of surface contamination in the vapor.