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In order to use High Harmonic Generation (HHG) as a light source of ultrashort pulses it is important to control the polarizatAn elegant solution to generate circularly polarized harmonics relies on combining circularly polarized fundamental with counter-rotating second harmonic.
In this work we numerically investigate the HHG process with bi-chromatic counter rotating circularly polarized laser fields by solving the Time-Dependent Schrödinger Equation for a 2D model of Neon atom.
The spectra of circularly polarized harmonics of atoms with 1s ground state is determined by the spatio-temporal symmetry of the laser field. However, Ne atoms have a ground state with non-vanishing angular momentum. Up to now its role in the process has not been investigated.
We show that the spectra from orbitals with non-zero angular momentum and from 1s orbital differ in two important ways. First, the height of left- and right- circularly polarized harmonics is different by an order of magnitude. Secondly, we show that using 2p orbitals a train of attosecond pulses with close to circular polarization is generated.
Finally, by using few-cycle drivers with controlled time delay between them, we theoretically demonstrate that isolated attosecond pulses with high ellipticity can be produced.
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