Thermal Analysis of GaAs-Based High Power Laser Diodes Related to Degradation

In this paper thermal characteristic and front facet of the 808 nm GaAs-Based laser diodes (LDs) before and after degradation are presented and discussed. The relation between thermal characteristic and the change of facet is analyzed. Aging tests are carried out under the conditions of the constant current stress (3 A), and the junction temperature of LD is fixed at 70°C. The total thermal resistance increases from 2.9 to 6.5 *C/W before and after degradation. Furthermore, the contribution of each component to the total thermal resistance has been obtained from the differential structure function and cumulative structure function. The thermal resistance of chip becomes slightly larger in magnitude after degradation than that before degradation, while significant increase in the thermal resistance of solder layer (indium attaching material) and package body is observed after degradation. In addition, some spots and lines of melted materials are observed using laser microscope after degradation, which lead to temperature increase of front facet and the optical power decrease. We can see that the total thermal resistance increase with the appearance of these spots and lines defect in facet of LDs. Consequently, from the results above we can conclude that the performance of LDs could be improved through optimizing of the front facet and package body of LDs.