Mode Clustering and Mode Hopping Phenomena in Multi-Quantum Well InGaN Blue Laser Diodes

We investigate the complex nonlinear dynamics of quantum well InGaN blue laser diodes that operate at 446-nm wavelength. For this purpose, we use the rate equation model of the multi-quantum well (MQW) semiconductor LD that considers two separate quantum wells with different carrier densities and includes self-, symmetric, and asymmetric cross-gain saturation and also Langevin noise sources regarding spontaneous emission, and carrier recombination are considered. We observe the periodic mode competition with operating dominant mode shifts from shorter to longer wavelength side through numerical simulation of the rate equation model. By tuning the gain saturation parameters, namely antiguiding factor and intraband relaxation time, we can get the single-mode operation from the periodic multimode hopping operation, which then changes to mode clustering operation. We, therefore, explains the mode clustering effect in terms of the gain saturation mechanism rather than the gain fluctuation. The simulation results presented and explained in this paper strongly agree with the previously published experimental findings.