CLADISS-a longitudinal multimode model for the analysis of the static, dynamic, and stochastic behavior of diode lasers with distributed feedback

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Abstract
A new computer model called CLADISS is presented for the analysis of multisection diode lasers. The model allows for the analysis of a wide variety of multisection devices with discrete or distributed internal reflections. The simulator can carry out a threshold, dc, ac, and a noise analysis. The threshold analysis determines the threshold of the various longitudinal modes of the laser. The power versus current and the wavelength versus current characteristics are found with the self-consistent dc analysis. In each of the dc bias points the dynamic ac analysis can calculate the FM and AM response of the laser, while the noise analysis can determine the frequency and intensity noise spectra, and the line shape of the longitudinal modes. Not only do the dc, ac, and noise analyses consider several longitudinal modes simultaneously, but they also take into account nonlinear gain suppression, spontaneous emission, and longitudinal spatial hole burning. CLADISS includes all of the longitudinal variations by dividing each laser section in many short segments. Both the optical field and carrier density are discretized according to this segmentation. To demonstrate the capabilities of CLADISS some nonlinear effects in DFB lasers are treated. We first consider instabilities induced in the side-mode suppression ratio by spatial hole burning. Next we discuss the effects of spatial hole burning and side modes on the FM response and on the linewidth. Finally, the model is used to calculate the linewidth floor due to the power dependence of the linewidth enhancement factor