ABSTRACT
A Y/Mo multilayer coating, optimized for top reflectivity at λ=12 nm, has been nano-inspected after long-term operation at the in-house soft x-ray laser. The surface and optical inspections were complemented by electron microscopy on cross sections, prepared with focused ion beam technology. A factor of 2.5 loss of reflectivity in the exposed area (ca. 30% relative loss every 100 shots), with concomitant nanoscale photodamage and particle fallout, was found. The x-ray-laser-induced damage extended as deep as 250 nm beneath the surface and as wide as the millimeter spot size.
ABSTRACT
Efficient amplification of coherent short-wavelength pulses along a plasma gain column requires traveling-wave excitation with the sweep velocity matched to the signal group velocity. Through simulations incorporating the gain dynamics of the system, we show that the group velocity is not constant but increases monotonically along the line focus due to strong saturation. We demonstrate a line-focusing configuration that results in traveling wave excitation with the sweep velocity well matched to the spatially varying group velocity. Moreover, we show through numerical simulations that the improved velocity matching yields a significant improvement in signal amplification.
ABSTRACT
A computational study of line-focus generation was done using a self-written ray-tracing code and compared to experimental data. Two line-focusing geometries were compared, i.e., either exploiting the sagittal astigmatism of a tilted spherical mirror or using the spherical aberration of an off-axis-illuminated spherical mirror. Line focusing by means of astigmatism or spherical aberration showed identical results as expected for the equivalence of the two frames of reference. The variation of the incidence angle on the target affects the line-focus length, which affects the amplification length such that as long as the irradiance is above the amplification threshold, it is advantageous to have a longer line focus. The amplification threshold is physically dependent on operating parameters and plasma-column conditions and in the present study addresses four possible cases.
ABSTRACT
We present the results obtained from three different setups of stable, diode-laser-pumped Nd:YLF lasers that operate in the TEM00 mode at 1053 nm and are passively mode locked by a saturable Bragg reflector. We obtained pulse widths tailored between approximately 70 ps and approximately 4 ns by using intracavity etalons of various thicknesses. With a maximum output power of 680 mW, we achieved an optical efficiency of 23%.
ABSTRACT
We report on the results of proton and gamma irradiation tests performed on nonlinear crystals for second- (SHG) and third-harmonic generation. Beta-barium borate (BBO), lithium triborate (LBO), and KTP crystals were exposed to three different energies of proton radiation (8, 70, and 300 MeV) and incremental doses of gamma radiation (up to 139 krad) in order to investigate the change in SHG performance and transmission spectra. BBO and LBO crystals turned out to be a suitable choice for SHG under radiative conditions.
