Influence of local heating on current-optical output power characteristics in Ga1−xAlxAs lasers

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Abstract
Available optical output powers from the Ga1−xAlxAs lasers are limited by the catastrophic optical damage or output power saturation due to local heating on the facet. Especially, the saturation of current-optical output power characteristically occurs during the operations at relatively low output power. This report describes the degradation process in an active region for lasers with the striped window as an electrode with respect to current-optical output power characteristics, electroluminescence image observation, and measurement of temperature rise at the facet and the cavity inside using laser Raman spectroscopy. The nonluminescing dark region observed in rapidly degraded lasers develops from the facet to the cavity inside. The dark region is so nonradiative that electron-hole recombination in that region produces heat rather than light. The measured local temperature on the facet drastically rises and the area influenced by local heating extends into the cavity inside. Although the threshold current increases by only 16%, the optical output power is saturated and finally the initial optical output power (20 mW/facet) is hardly maintained. It is found that the change in current-output power characteristics almost corresponds to the calculated results which incorporated temperture dependence of local absorption loss in the dark region.