Influence of sinusoidal modulation on mode competition and signal distortion in multimode InGaAsP lasers

摘要

This paper investigates influence of large-signal modulation on mode oscillation in InGaAsP/InP lasers. The mode competition dynamics under modulation are examined in terms of the temporal trajectories of the total output and the strongest modes as well as their Fourier spectra. The mode coupling induced by the strong spectral gain suppression is evaluated by both the correlation coefficients among the strongest modes and their signal distortion. We show that small and moderate modulations at the multimode hopping of the laser modulate the mode hopping along with modulation of each mode. The mode coupling is characterized by anti-correlation among the modes like as the non-modulated laser. Under modulation with the resonance frequency, the increase in the modulation depth changes mode coupling from anti-correlation to positive correlation and then to complete coupling that correspond to emission of periodic pulses. The mode coupling is characterized by mode competition distortion, which measures the amount of power carried by the mode signal at the frequency of multimode-hopping.