Theoretical investigation of elliptical high-order harmonic generation from ${\mathrm{H}}_2^{+}$ in two-color cross-linearly-polarized laser fields

We theoretically investigate the elliptical high-order harmonic generation from ${\mathrm{H}}_2^{+}$ in two-color cross-linearly-polarized laser fields by numerically solving the two-dimensional time-dependent Schrödinger equation. Numerical simulations show that the crossing-angle-dependent harmonic ellipticity exhibits a prominent antisymmetric structure, which tends to disappear as the internuclear distance increases. Furthermore, ground-state electrons experience resonant transitions to the first excited state at larger internuclear distances, where the disruption of symmetric electron motion suppresses the antisymmetric structure. Additionally, a near-circularly-polarized attosecond pulse can be obtained by modulating the crossing angle.