Characteristics and reliability of high-power InGaAs AlGaAs laser diodes with decoupled confinement heterostructure

In order to overcome catastrophic optical damage(COD), decoupled confinement heterostructure(DCH) featuring a broadened 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 Gamma(perpendicular to), quantum-well number N-w, keeping the beam divergence angle constant. COD level of various DCH lasers with uncoated facet was examined in 50 mu sec pulse operation and following results were obtained; COD was normalized by equivalent vertical beam width d/Gamma (perpendicular to) (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/mu m for InGaAs-QW and 40-50mW/mu m for GaAs-QW in the case of d/Gamma (perpendicular to) similar to 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 50 mu m aperture and 9.5W for 100 mu m aperture, which was limited by thermal saturation. Lifetest was carried out for 50 mu m aperture devices at the condition of 50 degrees 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 degrees 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 degrees C and 300mW-70 degrees C.