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An extraordinarily high degree of spatial coherence from a high average power tabletop 46.9 nm laser was observed in two-pinhole interference experiments. Refractive anti-guiding and gain guiding along a capillary discharge-produced plasma column causes a rapid increase of the spatial coherence with amplifier length. Full spatial coherence was approached with a 36 cm long plasma of very high axial uniformity and a length to diameter ratio exceeding 1000:1.

The capillary discharge ArIX laser (wavelength 46.9nm) is a new device attractive for various applications due to its unique for XUV lasers properties : high average power and compactness. Reflectometry and ellipsometry are among them. The first is capable to provide fundamental data on optical constants of solids, which are still rather limited. Reflection coefficient in this spectral range is highly sensitive to the presence of an overlayer at the surface of a sample. This hinders bulk optical constants determination, but offers the possibility to study chemical contamination by ambience. The theory of reflection from a surface with a thin overlayer is developed. It enables to rigorously include overlayer into reflectometry data processing and derive separately the parameters of bulk and overlayer. Ellipsometry in general is more powerful than reflectometry method to measure optical constants. In addition it offers the accurate methods to measure film thickness and properties of magnetic materials. Unfortunately high quality analyzers and polarizers are not available in this spectral range, which requires specific approach to ellipsometric measurements. We discuss and use for this purpose Sc/Si multilayer structures.

For many years researchers have envisioned the development of compact high repetition rate tabletop soft x-ray lasers that could be routinely used in application in numerous disciplines. With demonstrated average powers of several mW and millijoule-level pulse energy at 46.9nm, the Ne-like Ar capillary discharge-pumped laser is the first compact laser to reach this goal. In this paper we summarize the development status of high repetition rate tabletop soft x-ray lasers based on capillary discharge excitation, and give examples of their successful use in several applications. Results of the use of a capillary discharge pumped 46.9nm laser in dense plasma interferometry, soft x-ray reflectometry for the determination of optical constants, characterization of diffraction gratings, laser ablation of materials, and plasma generation are described. The observation of lasing at 52.9nm line in Ne-like Cl with output pulse energy up to 10 µJ is also reported.

We demonstrate the generation of a highly polarized soft-x-ray beam with a compact high-repetition-rate tabletop soft-x-ray laser. The radiation emitted by a high-average-power discharge-pumped tabletop Ne-like Ar soft-x-ray laser operating at 46.9 nm was polarized with a pair of Si/Sc multilayer mirrors designed for 45° operation. A degree of polarization greater than 0.96 was obtained. The polarized beam was used to characterize the efficiency of a diffraction grating. Intense polarized soft-x-ray radiation generated by compact tabletop sources has the potential to affect numerous other applications.

We report the demonstration of laser amplification at 52.9 nm in Ne-like Cl with a compact capillary discharge. Laser output pulses with energies of as much as 10 µJ have been obtained. The beam divergence was approximately 4 mrad. This new 23.4-eV tabletop laser is of particular interest for applications that require high peak fluxes of photons with energy slightly below the He photoionization threshold.