Theoretical analysis of 1.55-μm InAs/InP (113B) quantum dot lasers based on a multi-population rate equation model

Quantum dot (QD) lasers exhibit many useful properties such as low threshold current, temperature and feedback insensitivity, chirpless behavior, and low linewidth enhancement factor. The aim of this paper is to investigate the lasing spectra behaviour of InAs/InP(311B) QD lasers. In order to reach the standards of long-haul transmissions, 1.55-μm InAs QD lasers grown on InP substrate have been developed. More particularly, it has been demonstrated that the use of the specific InP(113)B substrate orientation when combined with optimized growth techniques allows the growth of very small (4 nm high) and dense (up to 10¹¹cm^-2) QD structures. Consequently, a model based on the multi-population rate equations (MPRE) taking into account many cavity longitudinal modes for the calculation of the entire emission spectrum has been developed. In order to include the inhomogeneous gain broadening of the QD ensemble, various dot populations, each characterized by a ground state (GS) and an excited state (ES) average energy level have been considered. It will be shown that the numerical results are in good agreement with the experimental ones, both for the case of the double laser emission and for the effects of the homogeneous broadening on the lasing spectra. This numerical investigation based on carrier dynamics is of prime importance for the optimization of low cost sources for optical telecommunications as well as for a further improvement of QD laser performances at 1.55-μm on InP substrate, as already demonstrated for InAs-GaAs QD lasers emitting at 1.3-μm.