Continuous wave AlGaAs laser diode bar parameters

Abstract

The development of separate confinement, heterostructure, semiconductor lasers diodes continues to be facilitated by the use of models. These models allow one to examine how the performance of a laser diode depends on epistructure growth and device processing parameters. In this way one can determine the optical and thermal constraints on a semiconductor laser's performance. For pulsed operation at low duty factor this is generally sufficient to design a laser diode system. Although the models are a good predictor of the initial performance of laser diode bars operated either in cw or a high duty factor mode, the performance degrades during the first 100 hours of operation. In our investigation of the design of cw operating, AlGaAs laser diode bars we have found that degradation mechanisms along with thermal properties provide design constraints. The problem which we have encountered is that a laser diode bar generally contains many independently emitting laser diodes. Each laser diode bar therefore has an unscreened population of laser diodes. In an unscreened population of laser diodes there are generally some which exhibit `infant mortality,' i.e., they cease lasing in the first 50 to 100 hours of on time. We have found that the `infant mortalities' among the laser diodes can significantly lower the yield of bars by reducing the number of emitting laser diodes on the bars below acceptable limits. The sources of this initial, rapid degradation of laser diode bars are discussed.