Abstract
We have constructed the ultrashort pulse vacuum ultraviolet (VUV) laser system with an optical-fieldinduced
ionization (OFI) Ar2* amplifier. The amplification properties of the OFI Ar2* amplifier were
evaluated. A gain-length product of 0.84 was obtained by using multi-pass amplification with a VUV
cavity. The gain-length product was increased up to 4.3 through the use of single-pass amplification
with a VUV reflector and a hollow fiber. We optimized temporal and spatial overlaps between a VUV
seed pulse generated as the 7th harmonic radiation and the OFI Ar2* amplifier. The optimal injection
time of the seed pulse into the OFI Ar2* amplifier was 20 ns, which agreed with a peak time of Ar2*
spontaneous emission. The spatially-resolved amplification of VUV seed pulses at 126 nm was observed
in an OFI Ar2* amplifier. The maximum amplification ratio of 3.1 was observed, which corresponded to
a gain value of 1.17 cm-1.
