Far-field behaviour of 980 nm broad area lasers incorporating bandgap widened extended slab waveguides

The far-field pattern of a broad area laser has been improved by placing passive, low-loss slab waveguides on either side of the active region. Two types of laser were investigated: first, control devices (75 μm×300-500 μm) with threshold currents of 200-250 mA and a broad far-field spectrum (10°) exhibiting several peaks; secondly, lasers with passive slab waveguides on both sides of the active region which exhibited a single peak in the far-field spectrum, the divergence of which decreased as the length of the passive sections was increased. The threshold current increased with increasing length of passive section, being typically 300 mA when the total length of the passive regions was 400 μm