Generation of intense isolated attosecond pulses at 100 eV

Rivas, Daniel E. (2016): Generation of intense isolated attosecond pulses at 100 eV. Dissertation, LMU München: Fakultät für Physik

Abstract

Originally limited to big facilities, nonlinear optics experiments in the extreme ultraviolet (XUV) spectral region with table-top systems are becoming a reality. These fundamentally different sources arise from a process known as high-harmonic generation (HHG). In this process, intense mid-IR to UV radiation is converted into the XUV to soft x-rays spectral region when interacting with a gas medium. The broad bandwidth supported by this process additionally allows the isolation of pulses with durations in the attosecond regime. However, given the low conversion efficiency of the HHG process, reaching the necessary XUV intensities to probe nonlinear effects has proven to be a challenging task. The initial investigations in this direction have been realized with photon energies up to 50 eV, by successfully scaling the XUV pulse energy through the use of multi-terawatt driving lasers. In this thesis, the generation and application of intense attosecond XUV-pulses in the 100 eV spectral region is presented. The XUV pulse energy increase is fundamentally enabled thanks to the development of a 16 TW optical-parametric synthesizer based on a two-color pumping technique, which provides pulse durations below two optical cycles. The achieved pulse energy, short pulse duration and the possibility to independently measure the carrier-envelope phase (CEP), makes this laser system a suitable driver of an XUV attosecond source. Through a careful energy scaling scheme, pulse energies above 20 nJ are routinely achieved in a spectrum spanning from 70 to 130 eV. A continuous spectral region is observed in single-shot between 100-130 eV for the appropriate CEP. This allows the isolation of attosecond pulses through spectral filtering. In addition to these high energies and broadband spectra, the reproducibility and long-term stability of the XUV beam makes it suitable for its use towards applications. As a proof-of-principle experiment, the XUV beam is focused to a measured beam size smaller than 3.1 micrometers,where the intensity is estimated to be above 10e13 W/cm2. At focus, the generation of Xe4+ and Xe5+ ions through the absorption of two photons is demonstrated. This is the first realization of such a measurement at these photon energies with a HHG source, paving the way to future attosecond time-resolved nonlinear spectroscopy of inner-shell electron dynamics.

Abstract

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Keywords: attosecond, high harmonic generation, optical parametric amplification, extreme ultraviolet, high intensity lasers.
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 530 Physik
• Fakultäten: Fakultät für Physik
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 17. November 2016
• 1. Bericht­erstatter:in: Krausz, Ferenc