In this work, we theoretically investigate the relative intensity noise (RIN) properties of quantum dot (QD) lasers through a rate equation model including the Langevin noises and the contribution from the off resonance energy levels. It is shown that the carrier noise significantly enhances the RIN which can be further reduced by properly controlling the energy separation between the first excited and the ground states. In addition, simulations also unveil that the RIN of QD lasers is rather temperature independent which is of prime importance for the development of power efficient light sources. Overall, these results indicate that QD lasers are excellent candidates for the realization of ultra-low noise oscillators hence being advantageous for fiber optics communication networks, short reach optical interconnects and integrated photonics systems.
This work theoretically investigates the four-level pulse-amplitude modulation characteristics of quantum dot lasers subject to optical injection. The rate equation model takes into account carrier dynamics in the carrier reservoir, in the excited state, and in the ground state, as well as photon dynamics and phase dynamics of the electric field. It is found that the optical injection significantly improves the eye diagram quality through suppressing the relaxation oscillation, while the extinction ratio is reduced as well. In addition, both the adiabatic chirp and the transient chirp of the signal are substantially suppressed.