Impact of Mode-Hopping Noise on InGaN Edge Emitting Laser Relative Intensity Noise Properties

In this paper, we report, through a comparative analysis of static and dynamic measurements, on the impact of mode hopping on the overall intensity noise dynamics of InGaN edge emitting lasers. Mode clustering usually observed in InGaN lasers enhances the mode competition and then the laser intensity fluctuation. Variations as large as 20 dB have been observed. The coexistence of longitudinal modes induces mode competition and then unstable bimodal lasing. This mode competition is mediated by the temporal fluctuations of spontaneous emission through the nonlinear cross saturation of the optical gain. The subsequent enhancement of the relative intensity noise can be detrimental for applications, where the intensity stability of InGaN lasers is a key parameter. Our experimental observations are supported by a simple rate equation model. We point out the major importance of the different modal gain in the bimodal regime on the overall intensity noise of the laser.