V P Konyaev

Study of strained-layer InGaAs/GaAs SQW RW lasers including analysis of internal coupling of modes and antiguiding effects

Low threshold strained-layer InGaAs/GaAs single quantum well (SQW) lasers are studied experimentally and analyzed on the basis of a computer model for the ridge-waveguide structure. The transition from the index guiding to the gain guiding is occurring with power anomalies provided by the antiguiding contribution of excess carriers. The mode gain is found to have a maximum attainable in the index-guided mode and a negative slope range in the dependence on the carrier concentration. If the operation point reaches the gain maximum the laser action can be ceased in the index-guided mode with power drop to the spontaneous level (lasing collapse) or to lower level of an antiguided mode. Mechanisms of the mode gain decrease are considered caused by a breakdown of the lateral index guiding and by an internal coupling of modes inside the diode chip, particularly of laser mode to cap layer mode. Latter has resonances at a phase synchronism of both modes accompanied a strong drop of the mode gain.

Brightness and filamentation of a beam from powerful cw quantum-well In{sub 0.2}Ga{sub 0.8}As/GaAs lasers

Near- and far-field patterns are studied for powerful (above 2-W cw output) quantum-well heterojunction InGaAs/AlGaAs/GaAs lasers. The maximum radiation brightness was 1.7107 W cm-2 sr-1. It is shown that the radiation filamentation is already observed 10 — 20% above the lasing threshold. The filamentation period decreases from 50 to 10 μm with increasing pumping current from almost the lasing threshold to an excess of 20% over the threshold. The filamentation results in the tenfold decrease in the radiation brightness of lasers compared to the theoretical value.

AlGaInP/GaInP visible laser diodes with extremely high characteristic temperature T0

Visible laser diodes (LD), based on AlGaInP/GaInP/GaAs material system, are of great interest, because of large scale application in the information reading and aiming. Heterostructures for such a type of LD were grown successfully by MOCVD. As mentioned by most authors the main problem, which has place during the growth technology developments, is low value of temperature threshold coefficient T0. This problem is due to low conductive band discontinuity and p-doping efficiency. Holes concentration in p- cladding layer determine T0 coefficient significantly, preventing leakage currents from active layer. Further it has been found, that hydrogen can passivate zinc atoms, incorporated into AlGaInP quaternary alloys. Comparing with AlGaAs/GaAs material system several new parameters should be controlled during AlGaInP layers growth: extent of ordering and growth rate. So, new degrees of freedom appears during growth and significantly affect growing results, epilayer parameters and, consequently, quality of manufactured laser diodes. This work is directed to show, how such growth parameters like: growth rate, growth temperature, and DMZn gas phase concentration; determine heterostructure quality.