Leonardo Brugnera

Publications (3)10.77 Total impact

• Article: Molecular internal dynamics studied by quantum path interferences in high order harmonic generation

  Amelle Zair, Thomas Siegel, Suren Sukiasyan, Francois Risoud, Leonardo Brugnera, Christopher Hutchison, Zsolt Diveki, Thierry Auguste, John W. G. Tisch, P. Salieres, Misha Y. Ivanov, Jonathan P. Marangos
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  ABSTRACT: We investigate how short and long electron trajectory contributions to high harmonic emission and their interferences give access to intra-molecular dynamics. In the case of unaligned molecules, we show experimental evidences that the long trajectory signature is more dependent upon the molecule than the short one, providing a high sensitivity to cation nuclear dynamics within 100's of as to few fs. Using theoretical approaches based on Strong Field Approximation and Time Dependent Schrodinger Equation, we examine how quantum path interferences encode electronic motion whilst molecules are aligned. We show that the interferences are dependent on channels superposition and upon which ionisation channel is involved. In particular, quantum path interferences encodes electronic migration signature while coupling between channels is allowed by the laser ?eld. Hence, molecular quantum path interferences is a promising method for Attosecond Spectroscopy, allowing the resolution of ultra-fast charge migration in molecules after ionisation in a self-referenced manner.
  10/2012;
• Article: Trajectory selection in high harmonic generation by controlling the phase between orthogonal two-color fields.

  Leonardo Brugnera, David J Hoffmann, Thomas Siegel, Felix Frank, Amelle Zaïr, John W G Tisch, Jonathan P Marangos
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  ABSTRACT: We demonstrate control of short and long quantum trajectories in high harmonic emission through the use of an orthogonally polarized two-color field. By controlling the relative phase ϕ between the two fields we show via classical and quantum calculations that we can steer the two-dimensional trajectories to return, or not, to the core and so control the relative strength of the short or long quantum trajectory contribution. In experiments, we demonstrate that this leads to robust control over the trajectory contributions using a drive field from a femtosecond laser composed of the fundamental ω at 800 nm (intensity ∼1.2×10(14)  W cm(-2)) and its weaker orthogonally polarized second harmonic 2ω (intensity ∼0.3×10(14)  W cm(-2)) with the relative phase between the ω and 2ω fields varied simply by tilting a fused silica plate. This is the first demonstration of short and long quantum trajectory control at the single-atom level.
  Physical Review Letters 10/2011; 107(15):153902. · 7.37 Impact Factor
• Article: Enhancement of high harmonics generated by field steering of electrons in a two-color orthogonally polarized laser field.

  Leonardo Brugnera, Felix Frank, David J Hoffmann, Ricardo Torres, Thomas Siegel, Jonathan G Underwood, Emma Springate, Chris Froud, Edmond I C Turcu, John W G Tisch, Jonathan P Marangos
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  ABSTRACT: We demonstrate enhancement by 1 order of magnitude of the high-order harmonics generated in argon by combining a fundamental field at 1300 nm (10(14) W cm(-2)) and its orthogonally polarized second harmonic at 650 nm (2 × 10(13) W cm(-2)) and by controlling the relative phase between them. This extends earlier work by ensuring that the main effect is the combined field steering the electron trajectory with negligible contribution from multiphoton effects compared to the previous schemes with 800/400 nm fields. We access a broad energy range of harmonics (from 20 eV to 80 eV) at a low laser intensity (far below the ionization saturation limit) and observe deep modulation of the harmonic yield with a period of π in the relative phase. Strong field theoretical analysis reveals that this is principally due to the steering of the recolliding electron wave packet by the two-color field. Our modeling also shows that the atto chirp can be controlled, leading to production of shorter pulses.
  Optics Letters 12/2010; 35(23):3994-6. · 3.40 Impact Factor