Repetitively actively gain-switched strongly asymmetric waveguide laser diode for high brightness picosecond pulse generation

We analyse theoretically the advantages of an asymmetric waveguide structure with a large equivalent spot size for use in a repetitively gain switched laser diode. The proposed construction, which maintains a single transverse mode, with a large equivalent spot size, for an arbitrary stripe width. This allows for a large carrier density to be accumulated before the onset of the optical pulse thus making for high pulse energy and also makes for a large modal cross-section which reduces the characteristic power for gain saturation and thus helps achieve high peak pulse power as well as energy. The predicted pulse energies are up to about 0.5 nJ from a narrow stripe laser (5 μm), with promises a significant improvement in the brightness of laser radiation compared to results in the literature. The possible effect of carrier transport is considered, and recommendations on the laser design in order to minimise it are given.