Modulation of ellipticity in HCN molecular high-order harmonic generation through laser polarization angles

Abstract

The elliptical polarization characteristics of high-order harmonic generation (HHG) are of great significance for the investigation of molecular dynamics and the development of new extreme ultraviolet light sources. In this work, the ellipticity of the HCN molecule HHG under different laser polarization angles is investigated using time-dependent density functional theory (TDDFT). The results indicate that the laser polarization angles can effectively control the ellipticity of HHG. When the laser polarization angles deviates from the molecular axis, the ellipticity of the HHG exhibits an asymmetric distribution. The analysis indicates that the physical mechanism by which the laser polarization angle regulates the ellipticity of high-order harmonics can be attributed to the switching of electron recombination trajectories under different laser polarization angles. The asymmetry of the molecular orbital electron density distribution directly affects the relative intensities of high-order harmonics parallel and perpendicular to the molecular axis, thereby achieving effective control of the elliptical polarization angles. This research provides new insights into the polarization property control of HHG in polar molecules under strong fields.