Enhancement cavities are passive optical resonators in which continuous-wave laser radiation or pulses of a frequency comb are coherently overlapped, allowing for a power and intensity scaling of up to several orders of magnitude. A prominent application is the table-top generation of bright, laser-like radiation in spectral regions where direct laser action is inefficient or not available at all, via intracavity nonlinear optical processes. However, to exploit the full capacity of this technique further progress is needed. This thesis covers central problems of enhancement cavities, such as finding limitations in scaling the circulating power, measuring cavity parameters with high accuracy, tailoring transverse modes and coupling out radiation generated in the cavity. Unprecedented intracavity laser powers were demonstrated, surpassing previous results by an order of magnitude. As an application, harmonics of the fundamental 1040-nm radiation up to the 21st order are generated. Besides reporting these fine experimental results, the thesis provides an excellent introduction into the physics of enhancement cavities, supported by more than 140 references.

This thesis presents research on novel laboratory-scale synchrotron X-ray sources based on inverse Compton scattering and applications of their X-ray radiation using the Munich Compact Light Source (MuCLS) as an example. It provides an introduction to the theory of this laser-electron interaction, laser resonators and X-ray interactions with matter. On this basis, upgrades to the laser system including the development of a new laser optic, X-ray beam stabilisation and two techniques for fast X-ray energy switching of inverse Compton sources are presented. On the application side, the beamline, designed and developed for the inverse Compton X-ray source at the MuCLS, is described before various techniques and applications are demonstrated at this laboratory-scale synchrotron X-ray facility. Among them are K-edge subtraction imaging, X-ray phase contrast imaging and X-ray absorption spectroscopy. Additionally, a new X-ray microscopy technique, called full-field structured-illumination super-resolution X-ray transmission microscopy, is presented. Apart from research conducted at the MuCLS, this thesis contains an in-depth overview on the state of the art of the various types of inverse Compton X-ray sources that have been realised so far. Accordingly, this thesis may serve as a guide and reference work for researchers working with inverse Compton X-ray sources as well as future users of such devices.

This book introduces readers to the development of a new generation of high pulse-repetition frequency instruments for multi-dimensional attosecond-resolution photoelectron spectroscopy (attosecond PES). It investigates the power scaling of femtosecond enhancement cavities for efficient intracavity high-harmonics generation (HHG). Further, it derives and verifies advanced resonator designs that feature large illuminated spots on all mirrors, which mitigate both intensity- and thermally-induced enhancement limitations. The dynamics of a high-finesse, passive resonator in the presence of a highly nonlinear optical process such as HHG are quantitatively investigated, both theoretically and experimentally. These investigations are instrumental in achieving the holistic optimization of the XUV source reported on here, which for the first time reached intracavity HHG conversion efficiencies comparable to those achieved in single-pass setups with a similar gas target. Coupling out the XUV beam from the enhancement cavity by purely geometric means, employing both the fundamental and higher-order transverse Gaussian modes, is studied. This offers the advantages of robustness, low distortion to the participating pulses, and photon-energy scalability. Last but not least, the author provides a range of proof-of-principle attosecond angle-resolved PES experiments. The book gives an outlook on the possible future development of cavity-enhanced HHG and an extensive discussion on the generation of isolated XUV attosecond pulses via intracavity wavefront rotation.

This thesis discusses the power scaling of ultrashort pulses in enhancement cavities, utilized in particular for frequency conversion processes, such as Thomson scattering and high-harmonic generation. Using custom optics for ultrashort-pulse enhancement cavities, it demonstrates for the first time that at the envisaged power levels, the mitigation of thermal effects becomes indispensable even in cavities comprising solely reflective optics. It also studies cavities with large beams, albeit with low misalignment sensitivity, as a way to circumvent intensity-induced mirror damage. Average powers of several hundred kilowatts are demonstrated, which benefit hard x-ray sources based on Thomson scattering. Furthermore, pulses as short as 30 fs were obtained at more than 10 kW of average power and employed for high-harmonic generation with photon energies exceeding 100 eV at 250 MHz repetition rate, paving the way for frequency comb spectroscopy in this spectral region.

This book provides a cutting-edge research overview on the latest developments in the field of Optics and Photonics. All chapters are authored by the pioneers in their field and will cover the developments in Quantum Photonics, Optical properties of 2D Materials, Optical Sensors, Organic Opto-electronics, Nanophotonics, Metamaterials, Plasmonics, Quantum Cascade lasers, LEDs, Biophotonics and biomedical photonics and spectroscopy.

This thesis provides unique information on the Kerr-lens mode-locking (KLM) technique applied to a thin-disk laser. It describes in detail cavity geometry, the qualitative approach to KLM, and self-starting behavior in the regime of both negative and positive dispersion. Comprehensive comparative analysis of KLM and semiconductor saturable absorber techniques is also carried out. Recent successful experiments on carrier-envelope phase stabilization, spectral broadening and compression of output of this oscillator underline the importance of this new, emerging technology.

Nonlinear Photonics and Novel Optical Phenomena contains contributed chapters from leading experts in nonlinear optics and photonics, and provides a comprehensive survey of fundamental concepts as well as hot topics in current research on nonlinear optical waves and related novel phenomena. The book covers self-accelerating airy beams, integrated photonics based on high index doped-silica glass, linear and nonlinear spatial beam dynamics in photonic lattices and waveguide arrays, the theory of polariton solitons in semiconductor microcavities, and Terahertz waves.