Threshold characteristics of epitaxial Al(Ga,As) surface-emitting lasers with integrated quarter-wave high reflectors

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Abstract
We report a study of threshold characteristics of as-grown surface-emitting lasers fabricated with molecular-beam epitaxy by the monolithic integration of two quarter-wave high reflectors (mirrors) of AlAs/Al0.4Ga0.6As surrounding an active spacer layer. The spacer was either a multiple quantum well of GaAs/Al0.4Ga0.6As (100 Å/200 Å) or GaAs. Several structures were grown corresponding to different mirror reflectance and different spacer thicknesses from ultrashort 0.9 to 10 μm. One of the structures was chemically etched to form a two-dimensional array of microlasers. All of the structures were photopumped at room temperature, and the lasing threshold was determined. Without any lateral confinement, the threshold irradiance was as low as 2×105 W/cm2. Near-field images of the light emitted slightly above threshold reveal several competing filaments. This competition broadens the lasing linewidth, but can be controlled by lateral confinement schemes.