The authors have compared AlGaAs∕GaAs∕GaN heterojunction bipolar transistors (HBTs) formed by wafer fusion with AlGaAs∕GaAs∕GaAs as-grown HBTs subject to high temperature annealing conditions similar to those used in the wafer fusion process. The high temperature annealing alone is found to cause gain degradation by a factor of 2–6, a result of reduction in minority carrier lifetime in the base. Detailed analysis indicates that the fused HBTs also suffer from higher recombination in the emitter-base junction, exacerbated base degradation as well as effective potential barriers formed at the GaAs base/GaN collector junction.

Short-cavity InGaAs/GaAs/AlGaAs lasers with first order DBRs and integrated EAMs were fabricated using a quantum well intermixing process. >5mW output was achieved at 45mA. DC extinction was >15dB at-1.5V with efficiencies up to 20dB/V.

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High power VCSEL arrays have experienced rapid growth and development. In this paper, we review the unique properties of VCSELs and present the progress that is making them very attractive for high power laser applications. INTRODUCTIONOver the past five to ten years, high-power vertical-cavity surface emitting laser (VCSEL) arrays have experienced rapid growth and development. Traditionally known for low-power applications such as short reach datacom links, recent work has shown VCSELs to be capable of high efficiencies and very high output powers. Coupled with that are the unique properties of VCSELs, such as circularly symmetric output beam, narrow spectral linewidth, and a low-cost fabrication model; high-power VCSEL arrays are becoming increasingly attractive for high-power laser applications such as solid-state pumping, welding, illumination, and printing, to name a few.The leading diode laser technology currently supplied to the marketplace is the edge-emitting laser (EEL), which boasts very high conversion efficiencies (60% -70%), and can be stacked to achieve kW-class power levels. While current VCSEL array efficiencies are typically <50%, other properties lend to potential improved system level performance and lower system level costs. This paper reviews the benefits of VCSELs and presents the current state of the art performance from VCSEL arrays.

Short-cavity InGaAsP/InP DBR lasers with integrated SOA and EAM were fabricated using a quantum well intermixing processing platform. >10mW output power and 17.5% wall-plug efficiency was achieved at 30mA. EAM extinction was >15dB at-4V.