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Recently, broad-area InGaAs-AlGaAs strained quantum well (QW) lasers have attracted much attention because of
their unparalleled high optical output power characteristics that narrow stripe lasers or tapered lasers can not
achieve. However, broad-area lasers suffer from poor beam quality and their high reliability operation has not been
proven for communications applications. This paper concerns reliability and degradation aspects of broad-area
lasers. Good facet passivation techniques along with optimized structural designs have led to successful
demonstration of reliable 980nm single-mode lasers, and the dominant failure mode of both single-mode and broadarea
lasers is catastrophic optical mirror damage (COMD), which limits maximum output powers and also
determines operating output powers. Although broad-area lasers have shown characteristics unseen from singlemode
lasers including filamentation, their effects on long-term reliability and degradation processes have not been
fully investigated. Filamentation can lead to instantaneous increase in optical power density and thus temperature
rise at localized areas through spatial-hole burning and thermal lensing which significantly reduces filament sizes
under high power operation, enhancing the COMD process. We investigated degradation processes in commercial
MOCVD-grown broad-area InGaAs-AlGaAs strained QW lasers at ~975nm with and without passivation layers by
performing accelerated lifetests of these devices followed by failure mode analyses with various micro-analytical
techniques. Since instantaneous fluctuations of filaments can lead to faster wear-out of passivation layer thus leading
to facet degradation, both passivated and unpassivated broad-area lasers were studied that yielded catastrophic
failures at the front facet and also in the bulk. Electron beam induced current technique was employed to study dark
line defects (DLDs) generated in degraded lasers stressed under different test conditions and focused ion beam was
employed to prepare TEM samples from the DLD areas for HR-TEM analysis. We report our in-depth failure mode
analysis results.
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