Coherent spin dynamics of electrons and holes in semiconductor quantum wells and quantum dots under periodical optical excitation: resonant spin amplification versus spin mode-locking

摘要

The coherent spin dynamics of resident carriers, electrons and holes, insemiconductor quantum structures is studied by periodical optical excitationusing short laser pulses and in an external magnetic field. The generation anddephasing of spin polarization in an ensemble of carrier spins, for which therelaxation time of individual spins exceeds the repetition period of the laserpulses, are analyzed theoretically. Spin polarization accumulation ismanifested either as resonant spin amplification or as mode-locking of carrierspin coherences. It is shown that both regimes have the same origin, whiletheir appearance is determined by the optical pump power and the spread of spinprecession frequencies in the ensemble.