Cavity competition in anomalous emission intensity in double-heterostructure (DH) lasers

(GaAl)As-GaAs double-heterostructure (DH) lasers frequently exhibit nonlinearity ("kink") in the current dependence of light output. It is shown that the "kink" is caused by laser-filament movement which can be translational, rotational, or both. The lasing spectra in the "kink" region shows two sets of longitudinal modes indicating simultaneous existence of two different cavities. The apparent filament movement is a result of the superposition of two radiation fields with one growing and the other diminishing in intensity. A model based on competition between two cavities induced by nonuniform gain distribution is proposed to explain the observed anomalies.