Fabrication of high-power diffraction-limited semiconductor tapered lasers and amplifiers

For the past several years, the generation of a high power near diffraction limited optical beam from a semiconductor laser has been one of the major interests of diode laser researchers. Such light sources with a good quality output beam will find applications in printing, biomedicine, nonlinear frequency conversion, efficient pumping of rare-earth doped fiber amplifiers and solid state lasers.; The most successful approach for obtaining high-power diffraction-limited output power from a diode laser is the tapered traveling wave laser amplifier configuration, which consists of a single-mode ridge waveguide and a tapered gain guided region. The design of the epitaxial layer structure and the schematic design of the tapered laser play a determining role in the performance of the device.; In this work, high-power diffraction-limited tapered lasers have been investigated and fabricated from various InGaAsP/InP based epitaxial layer structures at 1.55 μm. 1.9 W quasi-CW output power with ∼80% of the power in the central lobe from a diluted waveguide 4 quantum well wafer at 1.55 μm was obtained with a slope efficiency of ∼0.3 W/A corresponding to ∼37% differential quantum efficiency.; External cavity tapered lasers and amplifiers by implementing a single-angled facet curved ridge preamplifier at both 0.83 and 1.55 μm wavelengths were demonstrated for the first time. More than 1 W CW output power from the external cavity tapered laser was obtained with >50 dB side-mode suppression ratio around 0.83 μm with a tuning range from 0.795 to 0.855 μm. ∼1 W CW output power from the tapered amplifier was also obtained at 0.83 μm with ∼5 mW coupled input power. ∼0.3 W CW output power with ∼50 dB side-mode suppression ratio around 1.54 μm was demonstrated with ∼60 nm tuning bandwidth. These powers were found to be emitted in a near-diffraction-limited beam.