Identification of degradation mechanisms in high-power laser bars using by-emitter degradation studies

Abstract

An investigation into the degradation of an 808 nm AlGaAs/GaAs compressively strained high-power laser bar is performed using a range of experimental techniques that focus on understanding the performance of the individual emitters that make up the laser bar—a so-called by-emitter analysis. We find that thermally induced current runaway, beginning in the edge emitters, is an important factor in the degradation of this bar and its eventual failure. Facet temperature measurements reveal that temperature distributions where the emitters are hotter at the bar edges as compared to those in the bar centre can occur in aged laser bars. This is in contrast to the facet temperature distributions observed in new devices and also in measurements of the bulk temperature.