Generation of High Harmonics of Coherent Radiation in the Extreme Ultraviolet Spectral Range in the Low-Intensity Regime

Generation of high harmonics is the only available way to obtain coherent extreme ultraviolet (EUV) and soft X-ray radiation in laboratory conditions. We present a system for high harmonics generation and study of its parameters. Capillary waveguide filled with Ar gas is used to convert the pumping laser radiation from a Ti:Sapphire mode-locked femtosecond laser system. In the capillary the laser interacts with the gas and generates high harmonics of orders from 13 to 31 with good spatial coherence. In the relatively low-intensity regime (I ∼ 10 14 W/cm 2) we determined the optimum pressure for the genera-tion of high harmonics with our system to be 36 mbar of Ar gas.