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Resolving subcycle phase and amplitude modulation in strong-field ionization

Danish Furekh Dar1,*,†, Tao Chen2, Fang Liu2, and Stephan Fritzsche1,3

  • *Present address: School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China.
  • †Contact author: danishdar@sjtu.edu.cn
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Phys. Rev. A 114, 023104 – Published 12 August, 2026

DOI: https://doi.org/10.1103/61lb-rjd6

Abstract

Strong-field ionization in two-color (ω+2ω) elliptically polarized laser fields highlights subcycle electron dynamics in the angular distribution of photoelectrons. In these distributions, a characteristic alternating angular pattern is observed, in which successive above-threshold ionization peaks and sidebands exhibit opposite angular shifts and are controllable through the relative phase between the two driving fields. This pattern originates from subcycle interference between adjacent ionization bursts, where a weak-field-induced phase modulation changes sign from one subcycle to the next, thereby directly controlling the emission angle. We further identify abrupt sideband shifts arising from the sensitivity to the relative phase between the two fields. Time-dependent Schrödinger equation simulations show that the long-range Coulomb interaction selectively suppresses electron emission counterrotating with respect to the driving field, with a pronounced dependence on the field helicity. These results establish angular shifts as a direct observable of subcycle phase modulation and demonstrate their utility as a sensitive interferometric probe of attosecond electron wave-packet dynamics.

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Phys. Rev. A 114, 023104– Published 12 August, 2026
  • Received 28 May 2026
  • Accepted 30 July 2026
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