This book performs comparison of quantum-optical models to gain a deeper understanding of the semiconductor quantum dot laser (QDL) theory. There are contributions of the photon-assisted polarization and nonlinear Coulomb scattering on the turn-on dynamics. We study the turn-on dynamics of QDLs theoretically using two specific models, viz, those derived from master equations and rate equations. By use another model, we study the characteristic temperature and quantum efficiency in QDs microcavity. A factor is added to the s-shall population's equations and their theoretical simulation results present of the turn-on dynamics of InGaAs/GaAs QDL output lasing with CW wavelength of 1.3mim at room-temperature. This is including the photon-assisted polarization contribution. Other results present a theoretical simulation of the turn-on dynamics of InAs/GaAs QDL at the same wavelength driven by electrical current pulses. In this book a study of the confined-carrier level occupancy in a QD, threshold current density, characteristic temperature, certain temperature, and lowest excitation energy of QD with 1.55mim GaInAsP/InP QDL are presented.