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High-order harmonic generation in a driven two-level atom: Periodic level crossings and three-step processes

Faria, CFD; Rotter, I; (2002) High-order harmonic generation in a driven two-level atom: Periodic level crossings and three-step processes. PHYS REV A , 66 (1) , Article 013402. 10.1103/PhysRevA.66.013402. Green open access

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Abstract

We investigate high-order harmonic generation in closed systems using the two-level atom as a simplified model. By means of a windowed Fourier transform of the time-dependent dipole acceleration, we extract the main contributions to this process within a cycle of the driving field. We show that the patterns obtained can be understood by establishing a parallel between the two-level atom and the three-step model. In both models, high-order harmonic generation is a consequence of a three-step process, which involves either the continuum and the ground state, or the adiabatic states of the two-level Hamiltonian. The knowledge of this physical mechanism allows us to manipulate the adiabatic states, and consequently the harmonic spectra, by means of a bichromatic driving field. Furthermore, using scaling laws, we establish sharp criteria for the invariance of the physical quantities involved. Consequently, our results can be extended to a broader parameter range, as, for instance, those characteristic of solid-state systems in strong fields.

Type: Article
Title: High-order harmonic generation in a driven two-level atom: Periodic level crossings and three-step processes
Open access status: An open access version is available from UCL Discovery
DOI: 10.1103/PhysRevA.66.013402
Publisher version: http://dx.doi.org/10.1103/PhysRevA.66.013402
Language: English
Additional information: ©2002 The American Physical Society
Keywords: CYCLIC ORGANIC-MOLECULES, ATTOSECOND PULSE TRAINS, ULTRASHORT LASER-PULSES, STATIC ELECTRIC-FIELD, LANDAU-ZENER MODEL, 2-LEVEL ATOM, QUANTUM-WELLS, AVOIDED CROSSINGS, TEMPORAL PROFILE, IONIZATION
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/292055
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