Enabling elliptically polarized high harmonic generation with short cross polarized laser pulses

Enabling elliptically polarized high-order harmonics overcomes a historical limitation in the generation of this highly nonlinear process in atomic, molecular and optical physics with applications in other branches. Here, we shed new light on a controversy between experimental observations and theoretical predictions on the possibility to generate harmonics with large ellipticity using two bichromatic laser pulses which are linearly polarized in orthogonal directions. Results of numerical calculations confirm the previous experimental data that in short laser pulses even harmonics with large ellipticity can be obtained for the interaction of such cross-polarized laser pulses with atoms initially in a s- or p-state, while odd harmonics have low ellipticity. The amount of the ellipticity can be controlled via the relative carrier-envelope phase of the pulses, their intensity ratio and the duration of the pulses.

Automated summary

Enabling elliptically polarized high-order harmonics overcomes a historical limitation in the generation of nonlinear processes in atomic, molecular and optical physics. We shed new light on a controversy between experimental observations and theoretical predictions on generating large ellipticity harmonics using cross-polarized laser pulses. Numerical calculations confirm that even harmonics with large ellipticity can be obtained in short laser pulses, while odd harmonics have low ellipticity. The ellipticity can be controlled by the relative phase, intensity ratio and duration of the pulses.