  We propose a method to generate stabilized radio-frequency polarization
modulation based on optical frequency combs. Two pulse trains with the same
repetition rate and different offset frequencies generate arbitrary
polarization states that are modulated at the offset frequency difference.
Long-term stability of the polarization modulation is demonstrated with the
modulation frequency at frep/2. Modulation at frep/4 is also demonstrated to
show the flexibility of the technique. We employ an electrical delay line to
fine-tune the polarization states that constitute the time-dependent
modulation.
