Study of multielectron dynamics and structured laser beams in attosecond physics
- Luis Plaja Rustein Director
- Carlos Hernández García Director
Defence university: Universidad de Salamanca
Fecha de defensa: 24 May 2024
- Misha Ivanov Chair
- Óscar Zurrón Cifuentes Secretary
- Maria Teresa Flores-Arias Committee member
Type: Thesis
Abstract
This thesis work exploits the potential of ultrashort laser pulses to explore electron dynamics in matter and generate extreme ultraviolet (EUV) or soft X-ray emission in the form of attosecond pulses with customized properties. The strong-field ionization of atoms driven by high-intensity femtosecond laser pulses is the starting point for two physical phenomena covered in this thesis manuscript: the controlled generation of ring currents and high harmonic generation (HHG). A novel method, termed current-gating, is introduced to synthesize attosecond magnetic field waveforms by temporally confining ring currents induced by circularly polarized laser fields, representing a significant advancement in ultrafast magnetism. The rest of the thesis work focuses on HHG as a nonlinear optical process that offers great possibilities to track electron dynamics (including resonances or electron-electron correlation) and to map the tunable properties of low-frequency pulses into the EUV or soft X-rays. A second plateau extending to higher photon energies than the usual HHG is found as a spectral signature of correlated back-reaction during the laser interaction with He atoms. A multi-peak harmonic signature is identified as the trace of extremely fast attosecond Rabi oscillations driven by EUV femtosecond pulses in He atoms. In collaboration with experimental groups, the investigation of diverse HHG schemes driven by structured laser beams in macroscopic gas targets leads to high harmonic beams and attosecond spatiotemporal emission with unique properties of spin and orbital angular momentum. These configurations include the generation of scalar and vectorial high-harmonic vortex beams with high topological charge, circularly polarized high-harmonic vortex beams with steady/time-varying orbital angular momentum (i.e. self-torque), and attosecond vortex pulse trains. These spatiotemporal light structures in the EUV or soft X-ray extend the prospects of attosecond science and related quantum technologies for improved imaging and spectroscopic capabilities, paving the way for triggering and probing ultrafast angular momentum light-matter interactions.