Width of the emission line of injection lasers operating in a quasisingle-frequency regime

Theoretical and experimental investigations were made of the influence of the power of longitudinal resonator modes adjacent to the fundamental mode on the width of the emission line of injection lasers made from GaAlAs heterostructures with lateral optical confinement. The width of the emission line observed in the course of cw emission of real lasers was within the limits set by the homogeneous and inhomogeneous broadening of the gain profile. When the output power was ~ 5 mW from a face an increase (by up to 10%) in the relative power of the longitudinal modes adjacent to the fundamental one could broaden the line right up to the inhomogeneous limit. This effect was attributed to spatial depletion of the population inversion along the resonator axis.