ABSTRACT
Experiments dedicated to the characterization of plasma mirrors with a high energy, single shot short-pulse laser were performed at the 100 TW target area of the Z-Backlighter Facility at Sandia National Laboratories. A suite of beam diagnostics was used to characterize a high energy laser pulse with a large aperture through focus imaging setup. By varying the fluence on the plasma mirror around the plasma ignition threshold, critical performance parameters were determined and a more detailed understanding of the way in which a plasma mirror works could be deduced. It was found, that very subtle variations in the laser near field profile will have strong effects on the reflected pulse if the maximum fluence on the plasma mirror approaches the plasma ignition threshold.
ABSTRACT
Using an extended-cavity femtosecond oscillator, we investigated optical breakdown in BK7 glass caused by the accumulated action of many laser pulses. By using a pump-probe experiment and collecting the transmitted pump along with the reflected pump and the broadband light generated by the optical breakdown, we measured the build-up time to optical breakdown as a function of the pulse energy, and we also observed the instability of the plasma due to the effect of defocusing and shielding created by the electron gas. The spectrum of the broadband light emitted by the optical breakdown and the origin of the material modification in BK7 glass was studied. We developed a simple model of electromagnetic wave propagation in plasma that is consistent with the observed behavior of the reflection, absorption, and transmission of the laser light.
