Abstract
In order to overcome catastrophic optical damage(COD), decoupled confinement heterostructure(DCH) featuring abroadened waveguide and thin carrier block layers have been developed. Due to decoupling of carrier and optical confinement, a DCH laser can be designed more flexibly than a conventional separated confinement heterostructure (SCH) laser, i.e., laser diodes can be designed with a variety of gain coupling factor Γ⊥, quantum-well number N w , keeping the beam divergence angle constant. COD level ofvarious DCH lasers with uncoated facet was examined in 50μsec pulse operation and following results were obtained; COD was normalized by equivalent vertical beam width d/ Γ ⊥ (where d is thickness of quantum-well) and COD level of 980nm InGaAs quantum-well lasers was twice as high as that of 860nm GaAs quantum-well lasers, i.e., 100-110mW/μm for InGaAs-QW and 40-50mW/μm for GaAs-QW in the case of d/ Γ⊥∼1. So, COD level can be manage in DCH scheme. Epitaxial structure has been optimized through the high-power performance of gain guided multi-mode lasers. The CW maximum power 6.3W was attained for 50μm aperture and 9.5W for 100μm aperture, which was limited by thermal saturation. Lifetest was carried out for 50μm aperture devices at the condition of 50°C-1.0W. All 14 devices were operating over 13,000hrs without failure. The median life was estimated to be more than one hundred thousand hours at 50°C. Real index guided structure was fabricated with a multi-step MOVPE epitaxial growth. Stable fabrication could be possible even in a conventional process, since chemically active Al-content was greatly reduced at 980nm in DCH. The maximum CW output power was 1.3W, which was limited by thermal saturation. Single mode operation was extended up to 700mW. And 500mW kink-free output was reproducibly obtained in a self-aligned real index guide structure. Preliminary life tests showed the stable operation at 300mW-50°C and 300mW-70°C.
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