Amplification of subpico second UV pulses in the multistage GARPUN-MTW Ti:sapphire — KrF laser system

Terawatt 248-nm UV pulses with an energy of 0.62 J, a width of no more than 1ps, and a divergence of 20 μrad have been obtained in the first experiments on the GARPUN-MTW Ti:sapphire — KrF laser system at double-pass amplification of frequency-tripled pulses from the Ti:sapphire front end in wide-aperture electron-beam-pumped KrF amplifiers. The contrast of short pulses relative to the amplified spontaneous emission is found to be ~10⁶ for energy densities and ~10¹¹ for intensities. The specificity of short-pulse amplification in an active medium with fast population inversion recovery and advantages of amplification of trains of short pulses or short and long pulses are discussed. The peak power of single subpicosecond pulses in this laser system can be increased to 30TW, and the focused beam intensity can be as high as 10²⁰ W cm^-2.