Compact and efficient femtosecond supercontinuum sources based on diode-pumped solid-state lasers

This thesis deals with the realization of compact and multi-Watt femtosecond supercontinuum sources based on diode-pumped laser oscillators and highly nonlinear glass fibers. The main aspect of this work focuses on the development of directly diode-pumped sub-200 fs laser oscillators which are suitable as pump lasers for those fibers. In addition, a comprehensive study of the properties of supercontinua generated with pump wavelengths around 1 μm is presented. Micro-structured fibers, either tapered fibers or photonic crystal fibers (PCF), can convert narrow band laser light into multiple octave broad spectra. Average powers of several Watts and conversion efficiencies of more than 50% can be achieved. The properties of those spectra depend strongly on the input pulse duration. A particular feature of the femtosecond regime, which can be defined by an input pulse duration shorter than 200 fs, is a high spectral phase coherence. The main part part of this thesis describes the development of two diode-pumped sub-200 fs laser oscillators. On one hand, a very compact 20 MHz Yb:glass laser, on the other hand, a multi-Watt 44 MHz Yb:KGW oscillator. With the latter oscillator, we demonstrated to our knowledge the highest optical-to-optical efficiency of a diodepumped multi-Watt laser with a pulse duration of 150-170 fs. These advances are based on our study of Yb:KGW slab-oscillators pumped by broad-area laser diodes. The thermal effects in the Yb:KGW crystal slabs pumped by high-power broadarea diodes were investigated in detail experimentally as well as numerically. In the second part of this work, we studied the properties of supercontinua generated in tapered fibers with Ytterbium lasers with typical wavelengths around 1 μm. While the intensity noise and the influence of the fiber geometry on the spectra were found to be similar to former results achieved with Ti:sapphire lasers, a different influence of a pulse pre-chirp on the spectra was observed for Ytterbium lasers.