Resonant modes of GaAs junction lasers

The resonant modes of GaAs junction lasers are obtained from a proposed model and compared with experimental results. Theoretical results are based on an assumed laser medium whose dielectric constant varies both along and perpendicular to the junction plane. The frequency separations of the transverse modes are found to be in very good agreement with presented high-resolution spectral measurements of stripe-geometry laser radiation. Furthermore, the theoretical field distributions are also in good agreement with observed transverse field variations reported previously. The laser output spectrum usually shows a number of "satellites" located adjacent to each longitudinal (Fabry-Perot) resonance. It is shown that each satellite represents the frequency of a transverse resonance having a different mode number along the junction plane and a corresponding Hermite-Gaussian intensity profile along the plane. Theory shows that the frequency separation of two adjacent satellites is related to the falloff rate of the dielectric constant along the junction plane. This focusing is measured from the intensity profile of a far-field pattern. From this information, the theoretical frequency separation is calculated and found to agree well with the measured separation of 6.4 GHz (0.15 Å).