Study on catastrophic optical damage behavior of GaN-based high-power blue laser diodes

Facet degradation in blue GaN-based laser diodes operating at output optical powers exceeding 17 W is investigated. Facet coating failure in large optical cavity devices is shown to originate from an inhomogeneous temperature distribution at the front facet caused by non-uniform optical intensity across the emitting region under high-power operation. Localized heat accumulation leads to partial melting of the epitaxial material near the facet, and the resulting thermal stress induces coating delamination and spalling, constituting catastrophic optical damage (COD). Notably, the coating structure and interfaces within the damaged regions remain well defined after COD, indicating that failure is initiated by localized thermal degradation of the epitaxial material, which subsequently triggers coating failure. These results demonstrate that suppressing optical intensity non-uniformity or reducing the overall junction temperature is critical for mitigating facet COD in high-power GaN-based laser diodes.