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

摘要

The authors have investigated exoelectron emission from Nd-2laser glass,lithium niobate,lithium fluoride,and sodium chloride. Exoelectron emission was measured either with channel electron multipliers and single-pulse counting techniques,or with the aid of channel plate multiplier bundles having high gain and spatial resolution. The work was performed to gain information on general exoelectron properties of optical materials particularly after exposure to intense laser pulses below and just above the damage threshold and to assess the feasibility of exoelectron techniques as NDT methods for laser surface damage. LiNbO3exhibits a newly discovered effect subsequently termed 'thermally stimulated field emission of electrons.'In general,laser-induced exoelectron emission was either not observed at all (as in Nd-2glass and LiNbO3),found to be caused by unexpected plasma effects (as in LiF),or was too weak to be of any use as a NDT-technique. A phenomenological theory of the electron kinetic processes leading to electron trapping,exoelectron emission,and,ultimately,at very high photon fluxes,to intrinsic damage,was developed. (Modified author abstract)