Life studies of GaAs injection lasers

Life studies have been made to determine the effect of various factors, such as current density, optical flux density, and temperature on the degradation rate in GaAs injection lasers. The lasers were fabricated by H. Nelson using the liquid phase epitaxy method. In a group of tests a dual-diode laser structure was used which consisted of two diodes electrically isolated but optically coupled. The dual-diode structure makes it possible to determine the degradation in the diode lasing characteristics at operating current densities ewen though the degradation itself results from operation in a nonlasing mode. Broken life tests, in which the degradation rates were measured before and after a stepped change in current, were also performed to determine the effect of current density on the degradation rate. The results indicate that at a given current density, degradation is about the same whether or not the diode is lasing. Hence degradation is not peculiar to the lasing condition. The degradation rate is a super-linear function of current density and also a function of the state of the diode at a given time, for large rapid changes in the degradation rate which occur sporadically constitute a large share of the total degradation. The small degradation rate observed at 77°K is attributed to the lower operating current density which can be used at this temperature.