Optical initialization of hole spins in p-doped quantum dots: Orientation efficiency and loss of coherence

We study theoretically a recently proposed hole spin initialization scheme for p-doped quantum well or dot systems via coupling to trion states with subpicosecond circularly polarized laser pulses. We analyze the efficiency of spin initialization and predict the intrinsic spin coherence loss due to the pulse excitation itself as well as the phonon-induced spin dephasing, both taking place on the time scale of the driving laser pulse. We show that the ratio of the degree of dephasing to the achieved orientation effect does not depend on the pulse area but is sensitive to the temperature and detuning. The optimal excitation parameters are identified.