The investigation of laser-matter interactions calls for ever shorter pulses as new
effects can thus be explored. With laser pulses consisting of only a few cycles of the
electric field, the phase of these electric field oscillations becomes important for many
applications.
In this thesis ultrafast laser sources are presented that provide few-cycle laser pulses
with controlled evolution of the electric field waveform. Firstly, a technique for phasestabilizing
ultra-broadband oscillators is discussed. With a simple setup it improves the
reproducibility of the phase by an order of magnitude compared to previously existing
methods.
In a further step, such a phase-stabilized oscillator was integrated into a chirped-pulse
amplifier. The preservation of phase-stability during amplification is ensured by
secondary phase detection. The phase-stabilized intense laser pulses from this system
were employed in a series of experiments that studied strong-field phenomena in a
time-resolved manner. For instance, the laser-induced tunneling of electrons from
atoms was studied on a sub-femtosecond timescale.
Additional evidence for the reproducibility of the electric field waveform of the laser
pulses is presented here: individual signatures of the electric field half-cycles were
found in photoelectron spectra from above-threshold ionization.
Frequency conversion of intense laser pulses by high-order harmonic generation is a
common way of producing coherent light in the extreme ultraviolet (XUV) spectral
region. Many attempts have been made to increase the low efficiency of this nonlinear
process, e.g. by quasi phase-matching. Here, high-harmonic generation from solid
surfaces under grazing incidence instead from a gas target is studied as higher
efficiencies are expected in this configuration.
Another approach to increasing the efficiency of high-harmonic generation is the
placing of the gas target in an enhancement resonator. Additionally, the production of
XUV photons happens at the full repetition rate of the seeding laser, i.e. in the region
of several tens to hundreds of megahertz. This high repetition rate enables the use of
the XUV light for high-precision optical frequency metrology with the frequency comb
technique. With such an arrangement, harmonics up to 15th order were produced. A
build-up cavity that stacks femtosecond laser pulses in a coherent manner to produce
intra-cavity pulse energies of more than ten microjoules at a repetition rate of ten
megahertz is presented here...
Inhaltsverzeichnis (Table of Contents)
- Zusammenfassung
- Abstract
- 1 Introduction
- 1.1 Time-resolved spectroscopy
- 1.2 Optical frequency metrology with frequency combs
- 2 Ultra-broadband oscillators
- 2.1 Few-cycle Kerr-lens mode-locked Ti:sapphire oscillator
- 2.2 Chirped mirror technology for dispersion control
- 2.3 The carrier-envelope phase of a mode-locked oscillator
- 2.3.1 Measurement of the frequency comb parameters
- 2.3.2 CE phase stabilization by difference frequency generation
- 2.3.3 Control of the frequency comb parameters
- 2.3.4 CE phase stability characterization
- 2.4 Long-cavity chirped-pulse oscillators
- 2.4.1 Double-pass post-amplifier
- 2.5 Conclusions
- 3 Few-cycle chirped-pulse amplifier systems
- 3.1 CE phase-stabilized chirped-pulse amplifier system
- 3.1.1 Origins of CE phase noise of amplified pulses
- 3.2 Conclusions
- 3.1 CE phase-stabilized chirped-pulse amplifier system
- 4 Femtosecond enhancement cavities
- 4.1 Passive optical resonators for femtosecond pulses
- 4.1.1 Dispersion control
- 4.1.2 Electronic feedback techniques
- 4.2 Vacuum enhancement cavity at 10 MHz repetition rate
- 4.3 Conclusions
- 4.1 Passive optical resonators for femtosecond pulses
- 5 Applications
- 5.1 Spectroscopy experiments with frequency combs
- 5.2 High-order harmonic generation
- 5.2.1 High harmonic generation from surfaces
- 5.2.2 High-order harmonic generation in an enhancement cavity
- 5.3 Above-threshold ionization
- 5.4 Conclusions
- 6 Outlook
Zielsetzung und Themenschwerpunkte (Objectives and Key Themes)
This thesis presents the development and characterization of several ultrafast laser sources for time-resolved spectroscopy and optical frequency metrology. The primary objective is to achieve high-precision control over the carrier-envelope phase of few-cycle laser pulses. This control enables the study of strong-field phenomena that are highly sensitive to the waveform of the electric field.
- Phase stabilization of ultra-broadband laser oscillators
- Preservation of CE phase stability during amplification
- Development of enhancement cavities for femtosecond pulses
- Applications of phase-stabilized few-cycle pulses in time-resolved spectroscopy and frequency metrology
- High-harmonic generation from surfaces and within enhancement cavities
Zusammenfassung der Kapitel (Chapter Summaries)
- Chapter 1 introduces the research fields motivating the construction of the laser sources. This chapter discusses the importance of time-resolved spectroscopy and optical frequency metrology for exploring fundamental processes in matter.
- Chapter 2 presents various ultra-broadband laser oscillators, including a novel technique for stabilizing the carrier-envelope phase. This chapter also describes the development and implementation of chirped mirrors for dispersion control.
- Chapter 3 discusses the construction of a few-cycle chirped-pulse amplifier system with preserved CE phase stability. This chapter delves into the origins of CE phase noise in amplifier systems.
- Chapter 4 presents the design and setup of femtosecond enhancement cavities operating at 10 MHz and 100 MHz repetition rates. This chapter discusses the challenges of supporting the broad bandwidth of femtosecond pulses in optical resonators, including dispersion control and electronic feedback techniques.
- Chapter 5 focuses on applications of the developed laser sources. This chapter includes examples of spectroscopy experiments with frequency combs, as well as investigations of strong-field phenomena driven by intense few-cycle pulses, such as high-order harmonic generation from surfaces and within enhancement cavities, and above-threshold ionization.
- Chapter 6 provides an outlook on future research directions in the field of ultrafast laser science, highlighting the potential of enhancement cavities and Yb-based amplifier systems for advancing spectroscopy and frequency metrology in the XUV region.
Schlüsselwörter (Keywords)
This thesis is focused on phase-stabilized ultrafast laser systems for spectroscopy. Key terms include few-cycle laser pulses, carrier-envelope phase, frequency combs, high-order harmonic generation, above-threshold ionization, enhancement cavities, time-resolved spectroscopy, optical frequency metrology, and XUV spectroscopy.
- Quote paper
- Dr. Jens Rauschenberger (Author), 2007, Phase-stabilized Ultrashort Laser Systems for Spectroscopy, Munich, GRIN Verlag, https://www.grin.com/document/90151