Recent advances in short pulse oscillator technology have led to the reliable generation of pulses as short as 7-fs in duration[1]. Amplification of such pulses to only modest energies (~1 J), would produce peak powers (100 TW) and peak intensities (>1021 W/cm2) which are equivalent to or greater than those currently produced by the largest Nd:Glass based laser facilities. Futhermore low-energy, ultrashort-duration, high-peak-power systems could operate at repetition rates that are > 4 orders of magnitude higher, thus opening wide areas of high field, ultrafast phenomena to rapid investigation. Amplification of pulses on the order of 10 fs, however, is severely limited by two concerns: 1) control of higher order phase distortion and 2) gain narrowing during amplification.. In this paper, we present results of a three stage amplification system developed at the University of California, San Diego in which we address these problems with an optimized, quintic-phase-limited expander and compressor design and with regenerative pulse shaping. This system is designed to produce nearly-diffraction-limited, > 1-J pulses of ~15-fs in duration. To date the first two stages of amplification have produced, 18-fs, 4.4-TW pulses at a repetition rate of 50 Hz and an average power > 10 W before compression. To our knowledge, these intermediate results represent the shortest terawatt pulses, the highest expansion ratio (>100,000 times) and the highest average power yet produced by a chirped pulse amplification system.
