Interference effects in harmonic ellipticity from H2+ molecules in an orthogonally polarized two-color laser field

Abstract We theoretically investigate the elliptically polarized harmonics from aligned molecular ion H2+ in orthogonally polarized two-color (OTC) laser pulses. Our results show that a striking peak appears in the ellipticity curve of odd-order harmonics, and this peak shows obvious alignment dependence and shifts toward higher energy as the amplitude ratio of two colors increases. The location of the peak is close to that of the interference minimum predicted by using a modified model of dipole, indicating strong two-center interference effects in ellipticity. Through adjusting the frequency ratio of two colors, large ellipticity is obtained for both odd and even harmonics in a wide energy region. As a result, we synthesize a bright elliptically polarized isolated attosecond pulse with an ellipticity up to 0.63.