Lateral modes and self-oscillations in narrow-stripe double-heterostructure GaAl-As injection lasers

We present measurements of the radiation field, the mode spectrum, and the power characteristic of narrow-stripe (5 μm) proton-bombarded DH GaAs-AlGaAs injection lasers. We show that there is a correlation of these properties with the presence of self-oscillations. We conclude that lasers that display self-oscillations have a different lateral gain distribution from lasers that do not oscillate. With a simple three-by-three layer rectangular waveguide laser model we simulate the properties of the radiation field. We extend the model to include time-dependent carrier densities and a time-dependent number of photons in the mode. From the calculated response to fluctuations in current and spontaneous emission we explain the occurrence of self-oscillations and their dependence on the waveguide geometry.