Phasenabhängige Starkfeld-Laserphysik

• Applicant: Professor Dr. Gerhard G. Paulus
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2009 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 109096091

• Final Report Year: 2016

Final Report Abstract

In general this project has primarily facilitated advancements in two areas of strong-field laser physics. First, improvements in the ability to measure and control the phase of few-cycle laser pulses. Second, the development of theoretical treatments of electron and ionization dynamics in intense few-cycle laser pulses including elliptically polarized light and multiple ionizations. Both are fundamental to the field and will become more important as the push towards shorter pulses and higher intensities is only increasing together with the desire to explore these new regimes and the resulting phenomena. In addition to showing the robustness of our phase tagging technique in the exploration of phase phenomena in strong-field laser physics, we have advanced this tool is several significant ways. First, we have demonstrated and how one can use this technique to determine the absolute phase dependence of a process by referencing the carrier-envelope phase meter to ab initio calculations of the above-threshold ionization yield of atomic H. This removes much of the uncertainty associated with the unknown offset of typical relative phase measurements and allows for measurements of absolute phase offsets and not just relative phase dependencies. Additionally, we have demonstrated a method to measure the phase of TW and PW class laser systems and have made significant advances towards the goal of phase correction the fly, i.e. measuring and changing the phase of each and every individual laser pulse to the desired value. The realization of this goal will allow carrier-envelope phase measurement and control in a new regime of ultra-intense low repetition rate TW and PW class laser systems Our theoretical treatment of atoms in intense few-cycle laser fields has greatly benefited from our investigations of interactions over a wide range of laser parameters. By considering angular emission, few-cycle pulses, and field strengths strong enough to multiply ionize atoms and ions, we have been forced to move beyond simper models and address the complexities of these interactions while providing a coherent and unified picture of the dynamics in question. To do this we utilize semi-classical Monte Carlo trajectories that take into account a distribution of ionization times, transverse electron wavepacket spreading due to the tunnel exit, angular scattering from the Coulomb potential of the parent ion, multiple returns to the parent ion, and interference from classical action. These extensions to the semi-classical model have been tested and refined by our measurements under new and extreme conditions. As compared to quantum mechanical calculations, these semi-clasical trajectories yield much more readily available information about the dynamics in question, e.g. one can trace back the off-axis low-energy structures in above-threshold ionization to multiple returns of the ionized electron to the parent ion. Further, the extreme intensities necessary to multiply ionize an ion beam – which are numerical daunting for a quantum mechanical calculation – can be readily accessed with such a model. Finally, the relative computational simplicity and intuitive nature of this model makes it an ideal way to explore the possibilities of the ever increasing parameter space available to strong-field laser physics. In addition to significantly advancing the field of strong-field laser physics, this project has been successful in the production of high-quality peer-reviewed publications, the advancement of multiple students, and the fostering collaborations both within Germany and worldwide.

Publications

• “Dependence of high-order-harmonic-generation yield on driving-laser ellipticity”, Phys. Rev. A 86, 011401 (2012)
  M. Möller, Y. Cheng, S. D. Khan, B. Zhao, K. Zhao, M. Chini, G. G. Paulus, and Z. Chang
  
• “Coherent control at its most fundamental: carrier-envelope-phase-dependent electron localization in photodissociation of a H2+ molecular ion beam target”, Phys. Rev. Lett. 111, 093002 (2013)
  T. Rathje, A. M. Sayler, S. Zeng, P. Wustelt, H. Figger, B. D. Esry, and G. G. Paulus
  
• “Low-energy electron rescattering in laser-induced ionization”, J. Phys. B 47, 204022 (2014)
  W. Becker, S. P. Goreslavski, D. B. Miloševi´ , and G. G. Paulus
  
• “Multielectron effects in strong-field dissociative ionization of molecules”, Phys. Rev. A 89, 043429 (2014)
  X. Gong, M. Kunitski, K. J. Betsch, Q. Song, L. Ph. H. Schmidt, T. Jahnke, Nora G. Kling, O. Herrwerth, B. Bergues, A. Senftleben, J. Ullrich, R. Moshammer, G. G. Paulus, I. Ben-Itzhak, M. Lezius, M. F. Kling, H. Zeng, R. R. Jones, and J. Wu
  
• “Off-axis low-energy structures in above-threshold ionization”, Phys. Rev. A 90, 023412 (2014)
  M. Möller, F. Meyer, A. M. Sayler, G. G. Paulus, M. F. Kling, B. E. Schmidt, W. Becker, and D. B. Milošević
  
• “Accurate determination of absolute carrier-envelope phase dependence using photo-ionization”, Opt. Lett. 40, 3137 (2015)
  A. M. Sayler, M. Arbeiter, S. Fasold, D. Adolph, M. Möller, D. Hoff, T. Rathje, B. Fetić, D. B. Milošević, T. Fennel, and G. G. Paulus
  
• “Momentum-resolved study of the saturation intensity in multiple ionization”, Phys. Rev. A 91, 031401(R) (2015)
  P. Wustelt, M. Möller, T. Rathje, A. M. Sayler, T. Stöhlker, and G. G. Paulus
  
• “Laser-subcycle control of sequential double-ionization dynamics of helium”, Phys. Rev. A 93, 063421 (2016)
  M. S. Schöffler, X. Xie, P. Wustelt, M. Möller, S. Roither, D. Kartashov, A. M. Sayler, A. Baltuska, G. G. Paulus, and M. Kitzler