Nonlinearities in the emission characteristics of stripe-geometry (AlGa)As double-heterostructure junction lasers

Significant changes in the optical and electrical properties of stripe-geometry (AlGa)As double-heterostructure junction lasers have been observed to accompany a nonlinearity in the current dependence of the lasing emission. Over the nonlinear range, the optical field of the lasing emission shifts continuously with current toward one boundary of the active stripe. Simultaneously, effective gain saturation is lost and additional transverse modes are excited. The increasing gain is believed to occur primarily in spatial regions where the optical intensity is reduced as a result of the transverse motion of the field. Additional observations suggest that this transverse motion results from an interaction between the intense lasing field and the active medium. Consequently, gain depletion is discussed as a possible cause for the transverse instability. Implications of this model for a qualitative understanding of the improved output performance recently obtained from lasers with narrow stripes are also considered.