Two-color phase-of-the-phase spectroscopy with circularly polarized laser pulses

Abstract

Phase-of-the-phase spectroscopy using two-color colinearly polarized laser pulses has been introduced and experimentally applied to strong-field tunneling ionization in S. Skruszewicz et al., Phys. Rev. Lett. 115, 043001 (2015) and recently to multiphoton ionization in M. A. Almajid et al., J. Phys. B: At. Mol. Opt. Phys. 50, 194001 (2017). The idea behind phase-of-the-phase spectroscopy is to study in a systematic way the change in the photoelectron yield as a function of the relative phase between the strong fundamental field component (of carrier frequency ω) and a weak, second color component (e.g., 2ω). The observable of interest is the photoelectron-momentum-dependent phase of the change in the electron yield with respect to the relative phase, hence the name "phase of the phase." In the present paper, phase-of-the-phase spectroscopy is extended to circularly polarized light. With a small, counter-rotating 2ω-component, photoelectron spectra have a three-fold symmetry in the polarization plane. The same is true for the corresponding phase-of-the-phase spectra. However, a peculiar, very sharp phase-flip by π occurs at a certain radial momentum of the photoelectron that is sensitive to both laser parameters and the ionization potential. Results from the numerical solution of the time-dependent Schrödinger equation are compared to those from the strong-field approximation. An analytical expression for the momentum at which the phase-of-the-phase flipping occurs is presented.

Complete characterization of sub-Coulomb-barrier tunnelling with phase-of-phase attoclock

“…Mathematically, the value of Φ POP represents the waiting time (Φ POP < 0) or the passed time (Φ POP > 0) of the appearing instant of the yield peak with respect to the instant of φ RP = 0 during the yield oscillation. However, a clear physical meaning of Φ POP is not identified in previous phase-of-phase experiments [18][19][20][21][22][23] .…”

“…Recently, the phase-of-phase photoelectron spectroscopy was introduced to extract the scattering structural information of atoms, molecules and nanoparticles [18][19][20][21][22][23] , in which the momentum-resolved electron yield is Fourier transformed with respect to the relative phase between two-color laser fields to obtain the phase of the yield oscillation, which is the so-called phase of the phase. The phase-of-phase spectrum provides rich dynamical information than the static photoelectron spectra measured in the one-color field.…”

High-Harmonic and Terahertz Spectroscopy (HATS): Methods and Applications

“…He et al [51]). HATS is useful in determining the phase of the dual-color laser field in an all-optical way, which is easier to carry out than measuring the photoelectrons or ions [52][53][54]. The measured absolute optimal phase at 0.8π has significance, which is against the predictions from previously widely-adopted four wave mixing model and (plasma) current model.…”

Revealing laser-coherent electron features using phase-of-the-phase spectroscopy

“…The recently proposed phase-of-the-phase (PoP) technique [1] can serve as Occam's razor with respect to incoherent processes that spoil photoelectron spectra (PES). The general principle of the PoP and similar techniques is based on the irradiation of a target with a laser field that has a periodic parameter such as the relative phase between two fields with different colors [1][2][3][4][5][6][7][8][9] or the carrier-envelope phase [10]. However, in contrast to techniques where the forward-backward asymmetry [11][12][13][14][15][16] or side streaking [17][18][19][20][21][22] of the PES is analyzed at selected values of the periodic parameter, the PoP suggests to perform the Fourier transform with respect to this periodic parameter and to reveal how the PES follow it, e.g., whether the PES change with the same periodicity as the relative phase ("first harmonic") but a certain phase lag Φ 1 (the "phase of the phase"), twice per period ("second harmonic", with the corresponding phase lag Φ 2 ), and so on.…”