Development and application of high peak power ultrafast lasers.

Abstract

A compact, three-stage, multipass Ti:sapphire laser amplifier system has been developed that generates >40 TW pulses, with 24 fs pulse duration, at a repetition rate of 10Hz, and with an average power of 10 W. Output intensities in excess of 1 x 10<super>19</super> W/cm<super>2</super> have been produced. The technique of frequency-resolved optical gating was used to fully characterize the output pulses, and to carefully compare theoretical models with experiment. High dynamic range FROG measurements have been performed for the first time to characterize the temporal wings of the output pulses. Ultrafast lasers has been used to generate high-order harmonies. The shortest wavelength we observe, at 2.7 nm, is well within the water window region of x-ray transmission. In the case of all the noble gases, excellent agreement has been obtained between theoretical predictions for the highest harmonic photon energy generated and our experimental observations. We also observe that the individual harmonic peaks near the cutoff are well resolved for positively chirped pump pulses, but are unresolved in the case of negatively chirped excitation pulses. This behavior is explained by simulations that combine the chirp of the laser with the intrinsic phase shift of the harmonics. We have demonstrated that the intrinsic phase of the harmonic emission can be controlled by adjusting the chirp of the excitation laser pulse. Short wavelength recombinational x-ray lasers using high peak power ultrafast laser interaction with small clusters has also been investigated. A model has been developed to simulate this process. The model predicts that this is a feasible scheme to scale the recombinational x-ray laser to short wavelength. Experimental results have verified the hydrodynamic evolution predicted by this model.