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Continued progress in photon science demands advances in light source technology. For this purpose, this dissertation presents the generation and control of super-octave-spanning optical pulses based on dielectric chirped mirrors.
The generation of isolated attosecond XUV pulses and exploration of attosecond physics would strongly benefit from the availability of intense phase-stable optical waveforms custom-sculpted on the time scale of the light period. The pulse energy and bandwidth scalability of the driving optical waveforms depend on the precise dispersion control. In this work, various dispersion compensation techniques are introduced, and an unprecedented chirped mirror system with smooth dispersion control over 2-octave bandwidth is demonstrated based on an analytical analysis of dual-adiabatic-matching (DAM) structures. These mirrors are used in a sub-cycle optical waveform synthesizer supporting <2-fs multi-mJ-level optical waveforms over a super-octave bandwidth of 0.49 μm - 2.3 μm. The proposed designs benefit the development of advanced high-intensity sub-cycle parametric synthesizers and other ultrabroadband applications.
On the other hand, optical pulse trains from femtosecond mode-locked oscillators can be used as optical flywheels providing a very precise timing reference, opening up several interesting research areas in optical frequency metrology, such as optical clocks and ultra-low noise RF-sources. Few-cycle Ti:sapphire oscillators, featuring low quantum noise, are capable of generating octave-spanning spectra with ~1 nJ of pulse energy, enabling direct carrier-envelope-phase stabilization via f-2f self-referencing. In Chapter 4, the detailed spatiotemporal dynamics of few-cycle Ti:sapphire oscillators is studied by numerical analysis. Based on the spatiotemporal modeling, the laser cavity can act as an enhancement cavity to shape the spectral components via intracavity phase matching.
The phase-matching concept is also demonstrated experimentally, providing a >10 dB enhancement at the spectral wings while maintaining excellent beam quality, which is of great importance to improve the stabilization of optical flywheels and to seed ytterbium-based amplifiers for pumping high-power optical parametric (chirped-pulse) amplifiers. Furthermore, the developed spatiotemporal model can be implemented not only for studying octave-spanning oscillator dynamics but also for optimizing advanced ultrafast sources.
During my doctoral studies, a nonlinear light microscope system is also demonstrated. Nonlinear light microscopy is one of the most important applications in ultrafast photonics. For example, second-harmonic generation (SHG) microscopy is a promising candidate for detecting chiral crystals, so-called second-order nonlinear optical imaging of chiral crystals (SONICC). The feasibility of nonlinear light microscopy depends on the availability of robust femtosecond sources and reliable electronic control. We develop a nonlinear light microscope system based on femtosecond fiber lasers and high-speed electronics. With the demonstrated nonlinear light microscope, sub-μm resolution imaging at a video frame rate can be obtained with reduced excitation power compared with commercially available SONICC systems. With the developed ultrafast fiber laser technology and optimized electronic control, a custom-made nonlinear light microscope is constructed, which is capable of observing nucleation and growth kinetics of protein nanocrystals.
