Waveguiding in a stripe-geometry junction laser

Measurements of the magnitude and spatial distribution of the optical gain in a stripe-geometry junction laser are related to observations of the intensity profile along the junction plane of the same laser. We find that the width of the fundamental mode is in excellent agreement with a two-dimensional waveguide in which confinement along the junction plane is induced primarily by the optical-gain profile. The remainder of the confinement is consistent with a refractive-index profile established by a temperature distribution in the presence of defocusing by the free carriers. Within the two-dimensional model, we find no evidence of defocusing like that deduced previously for double-heterostructure lasers.