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edfas.org 25 ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 21 NO. 2 4. The free carriers are increasingly allowed to drift toward the surface and reach the non-radiative recombination center. 5. The absorption mechanism becomes stronger with additional heating of the facet. 6. The process continues until the facet melts due to the high temperature reached. 7. The defect ultimately extends from the facet inside the laser cavity to the point where stimulated emission does not occur anymore. The multimode character of the laser diodes making up the stacks means that a COD-induced burn on an emitter does necessarily affect the full emitter functionality. Typically, such limited burn only induces a partial localized extinction of the emitter. COD ANALYSIS The studied component showed as many as 24 emit- ters affected by COD out of 434 (red points in Fig. 6). As a first step, the functional impact of each COD was consid- ered. As seen in Fig. 6, all CODs do not affect the emitted power. Indeed, some emitters showing the physical COD signature did not suffer from a significant intensity decrease. In addition, no propagation of defects within a chip or within the whole component could be observed. These observations led to the conclusion that the com- ponent is resilient to an overstressed event. This is of critical importance because the resilience of the optical pumping function is crucial in a mission where no repair can be operated. The SEM inspection using a secondary electron detec- tor (for outlining the topologic contrast) unveils the fused aspect of the material (Fig. 7). The fused material is ar- ranged in aligned circular patterns related to the multi- mode character of the laser emission. Nodistinction could bemadewithSEMinspectionbetweenCODshavinga large Fig. 6 Intensity map of all the emitters of one laser diode stack. Fig. 7 SEM secondary electron images of CODs.