Theoretical Study Of Elliptical Polarized Attosecond Pulse Generation From Molecule Driven By A Strong Laser Field

With the development of laser technology,the intensity of the laser is increasing,which promotes the study of laser-matter interactions.The study of synthesized attosecond pulse based on high-order harmonics is one of the hot topics of research in strong field physics.In recent years,the elliptically polarized attosecond pulse has received a lot of attention.Compared to linearly polarized attosecond pulse elliptical polarized attosecond pulse provides additional degrees of freedom and is important for research in probing the chirality and structure of matter using the circular dichroism of photoelectrons.As a result,the generation of elliptically polarized and even circularly polarized attosecond pulses has been extensively exploredIn this paper,we systematically investigate the generation of elliptical attosecond pulses from molecules in strong laser fields,as summarized below:(1)We investigate the polarization properties of high-order harmonics from H2+by a linearly polarized laser.The results show that at 30°,the ellipticity of the harmonics has a maximum value and the intensity has a minimum value,which does not change with the laser parameters.For example,wavelength,half height full width and laser intensity.Calculation of the phase difference of harmonics of the x and y directions and the two-central interference effect of the molecule explains the harmonic ellipticity maximum and the harmonic intensity minimum,respectively.(2)We investigate the efficiency and ellipticity of high-order harmonics from different initial states of H32+ by a linearly polarized laser.The results show that the harmonic efficiency from the excited state is six orders of magnitude higher than that from the ground state driven by the same laser pulse.Moreover,the ellipticity of the harmonic from the excited state is higher,while the ellipticity of the harmonic from the ground is smaller and almost zero.We also find that by changing the polarization direction of the laser the ellipticity of the harmonics from the ground state and excited state is periodically distributed.And at certain laser polarization angles the ellipticity of the harmonics from the ground state is zero,which is related to the symmetry of the molecule.However,the ellipticity of the harmonics from the excited state is always non-zero,which can be attributed to the non-zero angular momentum of the excited state.