Mode dynamics and noise in modulated semiconductor lasers with strong gain suppression

Abstract

We analyze mode oscillation and noise of semiconductor lasers with strong asymmetric gain suppression and subjected to sinusoidal modulation. The mode competition (MC) due to strong gain suppression is measured by the correlation coefficients among the oscillating modes. We show that 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. Under weak and moderate modulation, the laser emits continuous and periodic signals characterized by mode competition distortion (MCD). This MCD drops to lower values by increasing the modulation depth. The frequency spectra of the relative intensity noise (RIN) exhibit sharp peaks at the modulation frequency and the higher harmonics. The increase in the modulation depth is associated with suppression of the total and modal RIN under high-frequency modulation but with noise enhancement under low-frequency modulation.