We proposed and demonstrated pre-chirp managed amplification (PCMA), in which the seeding pulse was nonlinearly amplified such that the amplified spectrum was substantially broadened. By properly pre-chirping the seeding pulse, the amplified pulse can be compressed with the duration much shorter than the transform-limited duration allowed by the seeding spectrum. Using an Yb-doped rod-type large-pitch fiber as the power amplifier, PCMA has enabled us to generate 75 MHz, ~60 fs, linearly-polarized pulses with >100-W average power.
We experimentally demonstrate phase-shaping in fiber CPA-systems, providing pulse-energies at the mJ-level. The
applied method is based on an analytical model describing the impact of SPM in CPA-systems. Using this phase-shaping
technique nearly transform limited pulses are produced at B-integrals up to 10 rad. Compared to a nonlinear CPAsystem
with the best performance being achieved by adjusting the compressor, operation of the same system using the
phase-shaping method permits peak-power enhancement by a factor better than 2.
In this work we present a new method for peak-power scaling in nonlinear CPA-systems. By clipping the tails of the
spectrum we demonstrate pulse quality enhancement and an increase of peak-power at the output of the CPA-system. A
theoretical model allows us to determine an optimal ratio between the spectral clipping bandwidth and the pulse
bandwidth at a certain B-integral. Additionally, a simple redesign of a grating based stretcher unit, applying our new
spectral clipping technique, would significantly increase the output peak-power of such nonlinear CPA-systems by a
factor up to six due to the higher stretching ratio.
To further scale the peak-power of state-of-the-art fiber CPA-systems, a careful optimization of the spectral as well as
temporal dynamics is required. The wavelength dependence of the small-signal gain, as well as the saturation of the
amplifier, strongly affect the signal bandwidth. For unsaturated amplifiers only a spectral optimization is required. It
can be shown that both the spectral center and the width of the input spectrum strongly affect the output bandwidth. An
optimization regarding these two parameters will be given. Design guidelines are presented. We develop a simple yet
efficient model to simulate the impact of saturation in broadband Ytterbium-doped fiber CPA-systems. Using this
model, we reveal that significant peak-power scaling up to 10 GW of current fiber CPA-systems is possible.
We experimentally demonstrate that circular polarization state is beneficial if the Kerr-nonlinearity has to be lowered
during the amplification of laser pulses. It can be shown that in a fiber-based chirped pulse amplification (CPA) system,
the use of circularly and linearly polarized light result in different B-integrals, which are measured using phase-only
pulse-shaping. The theoretical value of 2/3 for the ratio of the B-integrals of circularly and linearly polarized light is
experimentally confirmed. Circularly polarized light facilitates peak-power scaling, moreover, the self-focussing
threshold can be enhanced.
We derive an expression describing pre-compensation of pulse-distortion due to saturation effects in short pulse laseramplifiers.
The analytical solution determines the optimum input pulse required to obtain any arbitrary target pulse at the output of the saturated laser-amplifier. The relation is experimentally verified using an all-fiber amplifier chain that is seeded by a directly modulated laser-diode.
Pulse-contrast degradation at the CPA-system's output is analyzed. If Kerr-nonlinearity is present, weak initial spectral
phase and amplitude modulations are responsible for the decrease. The pulse is split into several sub-pulses. Bessel-functions
describe the intensities of the side-pulses relative to the principal pulse. We provide the governing physical quantities.
We report on an optical parametric amplification system which is pumped and seeded by fiber generated laser radiation.
Due to its low broadening threshold, high spatial beam quality and high stability, the fiber based broad bandwidth signal
generation is a promising alternative to white light generation in bulky glass or sapphire plates. As pump source we
propose the use of a high repetition rate ytterbium-doped fiber chirped pulse amplification system.
Noncollinearly phase-matched optical parametric amplifiers (NOPAs) - pumped with the green light of a frequency
doubled Yb-doped fiber-amplifier system <sup>1, 2</sup> - permit convenient generation of ultrashort pulses in the visible (VIS) and
near infrared (NIR)<sup> 3</sup>. The broad bandwidth of the parametric gain via the noncollinear pump configuration allows
amplification of few-cycle optical pulses when seeded with a spectrally flat, re-compressible signal. The short pulses
tunable over a wide region in the visible permit transcend of frontiers in physics and lifescience. For instance, the
resulting high temporal resolution is of significance for many spectroscopic techniques. Furthermore, the high
magnitudes of the peak-powers of the produced pulses allow research in high-field physics.
To understand the demands of noncollinear optical parametric amplification using a fiber pump source, it is important to
investigate this configuration in detail <sup>4</sup>. An analysis provides not only insight into the parametric process but also
determines an optimal choice of experimental parameters for the objective. Here, the intention is to design a
configuration which yields the shortest possible temporal pulse. As a consequence of this analysis, the experimental
setup could be optimized. A number of aspects of optical parametric amplifier performance have been treated
analytically and computationally <sup>5</sup>, but these do not fully cover the situation under consideration here.
We investigate supercontinuum generation with a femtosecond dual-pumping scheme. A 10 MHz oscillator delivering 300 femtosecond pulses at 1028 nm is frequency doubled and both the fundamental and second harmonic are coupled into a micro structured fiber. When the two pulses are temporally overlapped in the fiber a broad supercontinuum appears. By tuning the temporal delay between the two pulses, different regions of the spectrum can be enhanced which allows either improved flatness of the spectrum or selective amplification of regions of interest. The interesting result is shown to arise from cross phase modulation imposed on the visible pulse by fundamental solitons. Results from similar experiments with picosecond and nanosecond dual-wavelength pumping show the same qualitative behaviour and demonstrate that the governing mechanism in all cases is soliton fission and subsequent cross phase modulation of the co-propagating visible pulse.
Multi-beam confocal sectioned fluorescence lifetime imaging microscopy is demonstrated using a Yokogawa spinning disk. The single-photon excitation source is a supercontinuum generated from a Ti:sapphire seeded photonic crystalline fibre.