  Ballistic transport through nanoscale devices with time-dependent Rashba-type
spin-orbit interaction (SOI) can lead to spin-polarized wave packets that
appear even for completely unpolarized input. The SOI that oscillates in a
finite domain generates density and spin polarization fluctuations that leave
the region as propagating waves. Particularly, spin polarization has space and
time dependence even in regions without SOI. Our results are based on an
analytic solution of the time-dependent Schr\"odinger equation. The relevant
Floquet quasi-energies that are obtained appear in the energy spectrum of both
the transmitted and reflected waves.
