Investigation of size effect on the emission properties of InAs/GaAs conical-shaped quantum dot lasers

In this work the effect of size on the emission properties of InAs/GaAs conical-shaped quantum dot (QD) lasers coupled to wetting layer was investigated. At first, by use of numerical method of finite element and effective mass approximation, the Schrodinger equation for two types of QDs were solved and the envelop functions for the ground state, first excited state, and wetting layer state were obtained. Then, using the envelop functions, the transition dipole moments and spontaneous lifetimes were calculated and their dependence on size was investigated. In continue the output power of QD laser was calculated by use of semiconductor laser rate equations. The results show by increasing the QD size, the energy eigenvalues as well as the spontaneous lifetime decreases noticeably. We found out that the laser output decreases with increasing the size of QD. Respecting to this fact that the transition frequencies are also dependent on the size, the output frequency is revealed to shift by changing the QD size.