In this paper, a theoretical model is used to study the optical gain characteristics of quantum dot lasers. The model is based on the density matrix theory of semiconductor lasers with relaxation broadening. The effect of doping with varying the side lengths of the box in the structure is taken into account. A comparative study of the gain spectra of p-doped, undoped and n-doped structures of cubic quantum-dot (QD) laser respectively, is presented for various side lengths. The variation of peak gain on carrier density is also presented. The effect of side length on the variation in modal gain versus current density is plotted too. The results indicate that the p type doping is efficient to reach a better optical gain value, and to achieve low threshold current densities compared with undoped and n-doped structures, and the optimum value for quantum dot width to achieve the lower threshold current density for the three cases is L=100A .
Optical Gain and Radiative Current Density in Strain Compensated GaAsP/GaAsBi/GaAsP QWs Laser Structure
