High-order harmonic generation in laser-induced low-density plasma: past and recent achievements

High-order harmonics generation (HHG) in laser-induced plasmas is an advanced method for creating coherent radiation sources in the extreme ultraviolet region for different purposes. We review previous developments and recent advancements of this approach aiming at the high-order nonlinear spectroscopy of materials for studying the fundamental processes in micro- and macro-systems and developing the effective sources of coherent short-wavelength radiation. We discuss the implementation of advanced methods for the studies of materials through the analysis of their properties using the unique method of nonlinear spectroscopy related to HHG of ultrashort laser pulses in laser-ablated samples. The topics considered in this review include the determination and formation of the conditions for efficient HHG in laser-induced plasmas on the surfaces of various solid materials. The development of new approaches in the determination of the atomic and optical characteristics of materials through the application of the advanced methods allowing the growth of high-order harmonic yield using clusters, quantum dots, and nanoparticles, extended plasmas, two- and three-color pumps, resonance enhancement of single harmonic in the vicinity of strong ionic transitions, application of quasi-phase-matching conditions, etc., are reviewed. Finally, we discuss the potential goals of laser-ablation-induced HHG spectroscopy.