COHERENT PHASE-CONTROL OF FREE-FREE TRANSITIONS IN BICHROMATIC LASER FIELDS

We consider the coherent phase control of the nonlinear cross sections of induced and inverse bremsstrahlung in a powerful bichromatic laser field. The two field components have frequencies r omega and s omega, where r and s are small positive integers, and the relative phase psi of both components can be changed arbitrarily. Amending our earlier w ork on this problem (1993 Phys. Rev. A 47 715, 1993 Opt. Commun. 99 17 7) we show that for the ratios r:s = 1:2, 1:3 and 2:3 the phase-depend ent changes of the free-free cross sections are quite appreciable, whe reas for increasing values of s the phase dependence gradually disappe ars, assuming both field components have the same intensity. If, howev er, the intensity of the harmonic field component is considerably incr eased, phase dependent effects again show up even for larger values of s.