Laser-induced damage and ion emission of GaAs at 1.06 µm

This study focused on the multipulse laser damage and the subdamage threshold ion emission of GaAs. The initial goals were to determine the pulse-dependent damage threshold and to correlate ion emission with surface damage. A Q-switched Nd:YAG laser was used to irradiate the 100 line GaAs samples. Using values of N from 1 to 100, accumulation curves based on 50 percent damage probability were obtained. Corresponding damage threshold fluences were 0.4-0.8 J/sq cm for N greater than 1 and 1.5 J/sq cm for N = 1. Large site-to-site fluctuations in ions emission were observed and the onset of emission was found at 0.2 J/sq cm for all cases. Once surface damage occurred, ion emission increased greatly. The observed behavior supports a surface cleaning model for the ion emission which precedes surface damage. Measurements of linear and nonlinear free carrier absorption were made, but no anomalous absorption was observed.