Brightness and filamentation of a beam from powerful cw quantum-well In0.2Ga0.8As/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 1.7·10⁷ 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.