Elliptically polarized attosecond pulse generation by corotating bicircular laser fields

We revisit high-order-harmonic generation (HHG) in corotating bicircular fields, which possess high optical chirality, and extend the study to a frequency ratio higher than 1:2. By analyzing the classical trajectories in the corotating bicircular fields in the rotating frame, we show that the Coriolis-force effect that hinders HHG decreases with the frequency ratio. Given these features, we propose a method for producing highly elliptically polarized attosecond pulses (with ellipticity up to $\ensuremath{\epsilon}=0.88$) using the corotating bicircular field with a frequency ratio of 1:3. A comparison is also made with the extensively studied counter-rotating configurations with a frequency ratio of 1:2 considering various laser parameters. The results affirm the validity and superiority of the corotating configurations, from which both the ellipticity and yield of generated attosecond pulses are higher than those from the counter-rotating configurations.