Modeling spatial effects in multi-longitudinal-mode semiconductor lasers (original) (raw)

The multi-longitudinal-mode dynamics of a semiconductor laser is studied theoretically, based on travelingwave equations for the slowly varying amplitudes of the counterpropagating optical fields in the laser cavity, coupled to an equation for the carrier population dynamics. The model considers key ingredients describing the semiconductor medium, such as the spatial variations of the carriers and optical fields in the longitudinal direction, a parabolic frequency-dependent gain and phase-amplitude coupling, and does not assume a priori a fixed number of active longitudinal modes. We find deterministic out-of-phase modal oscillations which leave the sum of total modal intensities nearly constant. These oscillations become faster as the injection current increases, in good agreement with recent experimental observations. In our model the origin of modal oscillations is spatial hole burning in the envelope of the carrier grating, which is due to the interaction of different longitudinal modes. We also observe switching and hopping of the lasing modes in accordance with the experiments.