203 μa threshold current strained V-groove lasers

Abstract

Strained, self-aligned, and self-isolated V-groove lasers, operating near 980 nm with a minimum threshold current of 203 mu A, have been fabricated using molecular-beam epitaxy. The structures nominally employ Ga0.8In0.2As as the active gain medium. The lasing wavelength is a function of operating current and varies by a few nm. The far-field patterns are nearly circular. The characteristic temperature of the lasers is approximately=184 K and under application of external uniaxial stress from compressive to tensile conditions, the threshold current increases monotonically. Transmission electron microscopy reveals an increase in the well-width at the bottom of the grooves and a decrease along the walls. The low threshold current, lowest reported to date for a semiconductor laser, with or without the use of high reflectivity mirrors, and the other observations, are consistent with effects of single dimensionality due to confinement, effects of strain, and a reduction in parasitic recombination and leakage current. The optical power per facet is approximately 10 mu W and the 3-dB small-signal modulation frequency is below 10 GHz. The latter, lower than that of strained ridge laser structures, is believed to be dominated by capture and transmission-line effects.