Controlling sub-cycle electron dynamics with plasmonic bichromatic counter-rotating circularly polarised fields

The use of bi-chromatic counter-rotating laser field is known to generate high-order harmonics with non-zero ellipticity. By combining such a laser pulse with a plasmonic field, we propose a way to influence the sub-cycle dynamics of the high-harmonic generation process. Using a numerical solution of the time-dependent Schr{\"o}dinger equation combined with classical trajectory Monte Carlo simulations, we show that the change of the direction and the strength of the plasmonic field selectively enhances or suppresses certain recombining electron trajectories. This in turn modifies the ellipticity of the emitted attosecond pulses.