980-nm small-aperture tapered laser (1W CW, M2~3) and tapered arrays (>3W CW): comparison between GaInAs/(Al)GaAs quantum dot and quantum well structures

Quantum-dot index-guided tapered lasers and laser arrays of seven tapered emitters were developed for improved beam quality and wavelength stability. They are compared with one quantum well devices. These lasers have less than 30 μm output width and do not show any measurable astigmatism (<±10 μm). The structures were grown at the University of Wuerzburg using Molecular Beam Epitaxy (MBE). The quantum dot tapered laser emits 1W CW at 1.6 A with 0.74 W/A external differential efficiency, 39% maximum wall plug efficiency, and 110 mA threshold current. The quantum well tapered laser emits 1.1W CW at 1.5 A with 0.87 W/A external differential efficiency, 49% maximum wall plug efficiency, and 52 mA threshold current. The beam quality parameter at 1W is better for the quantum dot tapered emitter (M2=2.9) than for quantum well (M2=3.5). Quantum well lasers have the highest power and efficiency, but quantum dot lasers show better beam quality and a high wavelength stability.