X-ray Lasers, Plasma Properties and Harmonic Generation from Surfaces

Abstract

In this chapter, the basic principles of surface-excited X-ray lasers are discussed. We demonstrate the achievements reported during studies of two laser systems, 13 nm Ag X-ray laser and 18.9 nm Mo X-ray laser. We show the methods for analysis of the plasma properties at strong laser-surface interactions. We demonstrate how laser plasmas generated by femtosecond radiation on the surface of boron and molybdenum targets are investigated by the shadowgraph method. The occurrence of plasma bullets is discussed, which were observed on both singlepulse and multi-pulse interaction with the same area of a target. Backscattered 2ω and 3ω/2 harmonics generation during the interaction of femtosecond radiation with the surfaces of various targets is analyzed. The efficient second and threehalved harmonics were achieved for low-Z targets, whereas only second-harmonic generation was observed for high-Z materials. Finally, we consider various peculiarities of harmonic generation from the surface interfaces during interaction with ultra-strong laser fields.Keywords X-ray lasers · Plasma for X-ray lasers · Harmonic generation from surfaces · 18.9 nm laser · Molybdenum laser · Surface plasma · High excitation shadowgraphs · Backscattered 2ω and 3ω/2 harmonics · Low-order harmonic generation · Laser chirp