We theoretically investigate the influence of molecular alignment on elliptically polarized high-order harmonic generation (HHG) from ${\mathrm{H}}_2^{+}$ driven by an orthogonally polarized two-color laser field by numerically solving the three-dimensional time-dependent Schrödinger equation. Our findings indicate that the alignment of ${\mathrm{H}}_2^{+}$ along the laser propagation direction $(R\parallel z)$ leads to an enhancement in both the harmonic intensity and ellipticity compared with alignment along the laser polarization direction $(R\parallel x)$. Increasing the frequency ratio enhances both the ionization and recollision probabilities, thereby increasing the harmonic intensity. Furthermore, the relative phase enables control over the harmonic intensity, ellipticity, and quantum-path selection. We further demonstrate that the relative phase induces asymmetry in the electric field waveform, leading to a redshift of the harmonic spectrum that is closely associated with the enhancement of harmonic ellipticity. Finally, we synthesize a near-circularly polarized attosecond pulse train with an ellipticity of 0.99. Our study provides an effective route for experimentally controlling the polarization and intensity of molecular HHG.

Close

PrevNext

View figure in article

• Light-matter interaction
• Multiphoton or tunneling ionization & excitation
• Strong-field-induced spectra
• Molecules
• Schroedinger equation