Second-generation High-Order Harmonic Sources — From CPA to OPCPA

Sammanfattning: This thesis presents two sources of extreme ultraviolet (XUV) radiation based on high-order harmonic generation (HHG) in gases. The sources were developed for experiments requiring high-flux harmonic beams or HHG pulses at high-repetition rate. These were used experimentally to image nano-scale objects. The high-flux HHG source was used for digital in-line holography, and the high-repetition rate source for photoemission electron microscopy. In addition, a conceptual design for a high-flux gas beamline for a large scale facility, Extreme Light Infrastructure - Attosecond Light Pulse Source, is described. The work focuses on the construction and development of the driving laser systems and the HHG sources, as well as on the optimization of their performance. The thesis describes the two lasers used to drive the HHG sources: a high-power laser system and a newly built optical parametric chirped pulse amplification (OPCPA) system. The two systems are both based on the chirped pulse amplification technique, but the amplification process is carried out in different ways. The high-power laser system is based on linear amplification in Ti:Sapphire while the OPCPA system uses nonlinear amplification via difference frequency generation. Furthermore, the use of multi-color driving fields to manipulate the generation process, both from the microscopic and the macroscopic points of view, was investigated. The combination of the fundamental field with its second harmonic in a non-collinear geometry allows us to probe and control macroscopic properties. The addition of loworder odd harmonics in a collinear geometry results in an enhancement of the single atom response.