Feasibility Study of Exoelectron Imaging as an NDT Method for Laser Surface Damage of Nonlinear Optical Materials and Laser Glass.

摘要

The semi-annual report presents the results of a second six-month effort on the development of an NDT method to predict laser surface damage on dielectric materials used in high power laser systems. Experimental results on thermally and/or optically stimulated exoelectron emission from Nd-2laser glass,and NaCl and LiNbO3single crystals after electron bombardment or exposure to high peak power laser pulses are given. Computer calculations of the spatial variation of the density of trapped electrons after exposure of a pure NaCl single crystal to a high peak power pulse of a TEM(00) mode laser beam are reported and discussed. Experiments on exoelectron images from LiF surfaces are interpreted on the basis of these results. The role of a white-hot plasma in front of the examined LiF surface is described. New information on multiphoton free carrier generation,on free carrier absorption,and on their involvement in the exoelectron processes and in the surface damage mechanisms was obtained. (Author)