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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
The coherent spin dynamics of resident carriers, electrons and holes, in
semiconductor quantum structures is studied by periodical optical excitation
using short laser pulses and in an external magnetic field. The generation and
dephasing of spin polarization in an ensemble of carrier spins, for which the
relaxation time of individual spins exceeds the repetition period of the laser
pulses, are analyzed theoretically. Spin polarization accumulation is
manifested either as resonant spin amplification or as mode-locking of carrier
spin coherences. It is shown that both regimes have the same origin, while
their appearance is determined by the optical pump power and the spread of spin
precession frequencies in the ensemble
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