A GaInAsP/InP tapered-waveguide semiconductor laser amplifier integrated with a 1.5 mu m distributed feedback laser

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Abstract
A GaInAsP/InP index-guided type tapered-waveguide traveling-wave semiconductor laser amplifier (TTW-SLA) with exponential taper structure was realized for the first time and its integration with a 1.5 mu m wavelength phase adjusted DFB laser was demonstrated. A reasonable amount of the single-pass gain, which was limited by the residual reflectivity at the output end of the amplifier region, was obtained with no serious problem with the lasing spectrum. A narrow beam divergence of FWHM=5.5 degrees and stable longitudinal mode operation were obtained with the output waveguide width of 20 mu m by adopting both a window structure and 7 degrees angled facets. This value agrees well with the theoretically calculated one and proves that single transverse-mode propagation can be attained by an exponentially tapered TTW-SLA with a very wide output end.<>