High Harmonics with Controllable Polarization by a Burst of Linearly-Polarized Driver Pulses

Abstract

Abstract:We theoretically explore a scheme for generation of bright circularly and elliptically polarized high-order harmonics by bursts of linearly polarized pulses with a rotating polarization axis. Circularly polarized harmonics are formed if the bursts are comprised of N pulses that uphold an N-fold rotational symmetry, for N > 2. Rotating the polarization axes of the comprising pulses can generate elliptical harmonics with a collectively tunable ellipticity, from circular through elliptic to linear. The method preserves the single-cycle, single-atom and macroscopic physics of 'standard' linearly polarized high harmonic generation, with a high yield and cutoff energy. We investigate the method from a time-domain perspective, as well as a photonic perspective, and formulate the energy and spin-angular momentum conservation laws for this scheme. We find that the case of N = 4 is optimal for this method, resulting with the highest conversion efficiency of elliptical photons. The new features of this source offer new applications to helical ultrafast spectroscopy and ellipsometry.

Floquet group theory and its application to selection rules in harmonic generation

“…One approach to address this inconsistency is to use drivers that exhibit both spherical and elliptical DSs. A burst of linearly polarized pump trains 60,61 and a synthetic piecewise driver pump can conform to this condition (see SN 6 and supplementary Figs. 5, 6).…”

Photoelectron momentum distributions in the strong-field ionization of atomic hydrogen by few-cycle elliptically polarized optical pulses

“…The strong-field ionization (SFI) of atoms and molecules by intense femtosecond elliptically-polarized infrared (IR) pulses has attracted considerable interest in recent years. Besides leading to the generation of circularly polarized bi-harmonics [1][2][3][4][5][6], elliptical pulses have improved our understanding of fundamental strongfield processes, e.g., frustrated tunneling ionization [7] and multiphoton circular dichroism [8,9]. In particular, the attoclock setups [10][11][12][13][14][15][16][17], using either one-color or two-color elliptical pulses, have allowed us to access the phase [15], tunneling time [14], Wigner time delay [18], and the overall temporal evolution of an emitted electron wavepacket [15,19] in an intense IR field.…”