Generation and control of elliptically polarized harmonics in atoms interacting with two-color linear cross polarized pulses.

We have studied the generation of ellipticity in high harmonic generation in atoms with spherically symmetric ground states by two intense linearly polarized crossed beams, as observed recently in experiment [1]. Numerical simulations of the time-dependent Schrodinger equation as a function of their intensity ratio, relative phase, and pulse duration show that for sufficiently short pulse durations and experimentally feasible intensity ratios large amounts of ellipticity are possible. We describe the underlying physical mechanism and provide a model for how an experimentalist may tailor the ellipticity of their harmonics.

[1] G. Lambert et al., Nature Communications 6, 6167 (2015)