A theoretical investigation has been carried out for both the direct sinusoidal modulation and associated noise performance of InGaN based quantum well (QW) semiconductor laser diodes (LDs) operating in multimode. The study is based on the QW lasers with two separate quantum wells with different carrier injection ratios. A model of multimode rate equations is developed by taking into account both symmetric and asymmetric cross-gain saturation. Numerical simulation shows that the mode partition effect exists in both the modulated and unmodulated LDs. From modulation at microwave frequency, highly synchronized oscillation of the modes resulting periodic pulse-like output is observed that contains peaks at modulation frequency and its harmonics. Associated total RIN and modal RIN values suppress with the modulation index. The simulation results have well correspondence with the previously reported theoretical and experimental findings.
DUJASE Vol. 6 (2) 94-98, 2021 (July)
In this era, short-wavelength laser diodes with quantum-well (QW) structures offer plenty of opportunities for improvement in laser performance and receive widespread attention. Therefore, we develop dynamic model of the violet-blue InGaN laser diodes (LDs) and discuss basic features of the device in this paper. We investigate longitudinal mode dynamics through detail numerical simulation of the rate equation model of the quantum-well LDs. We selectively observe several effects such as relaxation oscillation, mode competition, intensity noise etc. From the dynamic behavior of the gain spectrum and time-varying modal photon numbers we found that the higher intensity noise of the quantum-well structure was due to random fluctuation with time among the different modes. The results were explained considering the previously published findings to confirm the validity of the proposed rate equation model of the quantum-well structures.
DUJASE Vol. 7 (2) 62-67, 2022 (July)
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