Accumulative Damage of GaAs and InP Surfaces Induced by Multiple-Laser-Pulse Irradiation

Nd:YAG laser multiple-pulse irradiation to GaAs and InP crystals with n- and p-type conductivities was studied. The laser pulse photon energy is below the band gap energies of GaAs and InP. The laser power fluence and number of pulses that cause surface damage correlate. The obtained accumulation curves have two characteristics. The number of pulses increases steadily as the fluence decreases. Above the critical fluence F c , optical damage occurs; below F c , no surface damage due to irradiation with a few thousand laser pulses occurs. The difference between the laser power fluences of GaAs and InP is less than 30%. A clear doping property dependence of the accumulation curves is observed for the first time. Results of the analysis of the absorption coefficient dependence indicate optical absorption other than free-carrier absorption. This process was quantitatively evaluated as the residual absorption coefficient, leading to the quantitative analysis of catastrophic optical damage in laser diodes.