Narrow-beam divergence 1.3-μm multiple-quantum-well laser diodes with monolithically integrated tapered thickness waveguide

This paper describes the optimum design, fabrication, and performance of a 1.3-μm multiple-quantum-well (MQW) laser diode monolithically integrated with a tapered thickness spot-size transformer. The dependence of the lasing characteristics on the thickness distribution of the core layer and on the current injection profile of the device were analyzed. This integrated laser with its optimized structure performed at a low threshold current of 22.2 mA, even at 85°C. The integrated spot-size transformer effectively reduced the lateral and vertical far-field FWHM´s to 8° and 9°, respectively. A very long lifetime of over 1×10⁵ h was estimated at 85°C and 8 mW under CW operation