TRANSIENT MULTIMODE DYNAMICS IN NEARLY SINGLE-MODE LASERS

The transient dynamics of nearly single-mode semiconductor lasers is studied analytically and numerically for lasers biased below threshold. The side-mode excitation probability is evaluated by solving a Fokker-Planck equation approximately. The validity of the approximate solution is verified through Monte Carlo simulations of the corresponding Langevin equations. The results show the relevance of the carrier-density overshoot during laser turn-on in determining the side-mode excitation probability. They also indicate the dependence of this probability on various device parameters such as the gain margin between the main and side modes. The experiments performed by using distributed feedback (DFB) semiconductor lasers show qualitative agreement with theory. The experiments also suggest that the inhomogeneous nature of the carrier-density distribution may be important for understanding the transient multimode dynamics in DFB lasers.