  We consider a monoenergetic beam of moving charged particles interacting with
two separated oscillating electric fields. Time-periodic linear potential is
assumed to model the light-particle interaction using a nonrelativistic,
quantum mechanical description based on Gordon-Volkov states. Applying Floquet
theory, we calculate transmission probabilities as a function of the laser
field parameters. The transmission resonances in this Ramsey-like setup are
interpreted as if they originated from a corresponding static double-potential
barrier with heights equal to the ponderomotive potential resulting from the
oscillating field. Due to the opening of new "Floquet channels," the resonances
are repeated at input energies when the corresponding frequency is shifted by
an integer multiple of the exciting frequency. These narrow resonances can be
used as precise energy filters. The fine structure of the transmission spectra
is determined by the phase difference between the two oscillating light fields,
allowing for the optical control of the transmission.
