Catastrophic optical damage to edge-emitting diode lasers: A holistic approach

Catastrophic optical damage (COD) remains a defining reliability challenge in high-power edge-emitting diode lasers, continuing to limit power density and operational lifetimes despite decades of progress. COD is irreversible and occurs preferentially, but not exclusively, at high-power densities. The understanding of the physical mechanisms leading to the COD constitutes a step forward for making more power devices able to operate safely for thousands hours. We provide a review of COD in devices made from various material systems (GaAs, GaN, and InP), and the explanations of the various microscopic processes related to its occurrence. COD is launched by the formation of local hot spots, preferentially, but not only, at the light exit aperture of devices. The COD is described as a complex non-linear effect involving optical, thermal, mechanical, and electrical phenomena. The properties of the materials sensitive to the degradation and the experimental techniques for identifying the degradation fingerprint are also treated. A critical insight is the central role of the facet region, where optical loading, native oxides, and defect structures converge to initiate the failure. Recent mitigation strategies have significantly raised COD power thresholds. This review provides the recent developments underscoring a multifaceted approach combining surface engineering, passivation, and device design to suppress COD. Nevertheless, it is to be expected that in the quest to achieve ever lower costs in cents/W of emission power, the presence COD will remain a feature of future generations of devices, requiring continued close attention.