Influence of the Spectral Gain Suppression on the Intensities of Longitudinal Modes in 1.55 μm InGaAsP Lasers

The self-suppression and both symmetric and asymmetric crosssuppressions
of the gain of longitudinal modes have been analyzed in InGaAsP
lasers emitting in wavelength of 1.55 μm based on a third-order perturbation
approach. We compared the influences of such suppression effects of gain on
the time variations of the mode intensities and the associated output spectra.
Such study was based on numerical integration of the laser rate equations in a
multi-mode model. Based on intensive simulations of mode dynamics, we
explored the operating regions of the single- and multi-mode operations over a
long scale of the strength of the asymmetric gain suppression. The results
showed that the competition among the modes induces normal multimode
operation under self suppression, single-mode operation in the central mode of
the gain spectrum under symmetric cross-suppression, and single-mode
operation with jumping of the lasing mode to the long-wavelength side of the
spectrum under asymmetric gain suppression. When the asymmetric gain
suppression is enhanced, transient multi-mode switching is stimulated showing
asymmetric multi-mode output spectra in good correspondence with
experimental results.