Amplification of subpicosecond UV pulses in XeCI excimers

Abstract

A two-stage XeCI amplifier chain was utilized to characterize the amplification of subpicosecond laser pulses in this medium. The UV seed pulses were formed by compression1 (to 0.5 ps), the 6-ps pulses from a commercial synch-pumped dye laser tuned to 616 nm, amplifying selected pulses (at 10 Hz) in a Nd3+: YAG pumped dye amplifier chain, and frequency doubling the amplified pulses in a 1.5-mm KDP crystal. The measured seed pulse spectral width was 50 cm-1. A 0.75-m lens placed before the first excimer brought the pulses to a gentle focus in an evacuated region 1-m downstream from the amplifier. An aperture placed at this point prevented ASE from reaching the second amplifier. The small signal gain in the first amplifier was 700, the amplified pulse energy was 0.5 mJ, and the pulse width (measured using an autocorrelation technique based on two-photon ionization in DABCO vapor) was 0.4 ps. A plot of output vs input pulse energies for a collimated 0.2-cm2 beam in the second amplifier showed the saturation parameter to be 2.1 mJ/cm2. This implies that single pulse energies in excess of 30 mJ and intensities in excess of 6 × 1010 W can be produced with this system. Intense self-phase modulation of the beam was readily observed to occur in air, producing a 1000-2000-cm-1 wide UV continuum.