High-intensity pulse compression with plasma nonlinearity

Ultrashort pulses are very important in the research of high field physics. The scheme of extracavity compression in gas-filled hollow fibers has been used to generate 0.1TW/5fs laser pulses successfully. However, the ionizat ion of medium limits the energy of pulses to be compressed in hollow fibers filled with noble gases. Gabriel Tempea et al suggested that plasma nonlin earity can be used to compress the pulse. In this paper, we investigate the possibility of compressing a 50fs, 10mJ pulse with this scheme. We discuss the pulse compression when the ionization of the inner surface of a hollow fiber occurs. Based on numerical simulation, we find that the pulse can be compressed to 5fs after its propagation through the hollow fiber filled wi th noble gases. The spectral width of the pulse exceeds 200THz and its phas e distribution is near the quadratic curve, which can be phase-compensated easily by using chirped mirrors. Also we find that the pulse compression is very sensitive to the gas density in the hollow fiber. The ionization of t he inner surface of the large hollow fiber is dominant (about 20-30%) for t he energy loss comparing with the phase modulation due to neutral atoms. We find that a lower gas density is enough for the phase modulation, so the e nergy loss due to gas ionization is less pronounced.