Generation of millijoule-level soft-x-ray laser pulses at a 4-Hz repetition rate in a highly saturated tabletop capillary discharge amplifier

Includes bibliographical references (page 1117).Laser pulses with energies of as much as 1 mJ were generated at a wavelength of 46.9 nm by single-pass amplification in a 34.5 cm-long Ne-like Ar capillary discharge plasma. The large gain-length product of this plasma column allows for soft-x-ray amplification in a highly saturated regime, resulting inefficient energy extraction. Average laser output pulse energy of 0.88 mJ and peak power of 0.6 MW were obtained at a repetition rate of 4 Hz. With an estimated peak spectral brightness of ≈1 × 1023 photons/s mm2 mrad2 0.01% bandwidth) this tabletop laser is one of the brightest soft-x-ray sources to date

Measurement of the spatial coherence buildup in a discharge pumped table-top soft x-ray laser

Includes bibliographical references (page 2802).We have measured the variation of the spatial coherence with plasma column length in a saturated table-top 46.9-nm Ne-like Ar capillary discharge soft x-ray amplifier for lengths up to 16.4 cm. The measurements, which are in good agreement with time dependent wave-optics model computations, provide the first experimental evidence of a monotonic increase of the coherence with length in a soft x-ray amplifier. The variation of the coherence across the beam profile was also studied. Off axis, the coherence is larger in the tangential than in the radial direction

Focusing of a tabletop soft-x-ray laser beam and laser ablation

Includes bibliographical references (page 1716).We focused the beam of a high-repetition-rate capillary-discharge tabletop laser operating at a wavelength of 46.9 nm, using a spherical Si/Sc multilayer mirror. The energy densities significantly exceeded the thresholds for the ablation of metals. Single-shot laser ablation patterns were used in combination with ray-tracing computations to characterize the focused beam. The radiation intensity within the 2-μm-diameter central region of the focal spot was estimated to be ≈1011 W/cm2, with a corresponding energy density of ~100 J/cm2

Prospects of reflectometry and ellipsometry with Colorado State University tabletop XUV laser, The

Includes bibliographical references (page 457).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 over layer 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

Two-dimensional near-field and far-field imaging of a Ne-like Ar capillary discharge table-top soft-x-ray laser

Includes bibliographical references (page 1514).We have performed systematic measurements and numerical modeling of the divergence and exit beam size of a 46.9 nm Ne-like Ar capillary discharge pumped soft-x-ray amplifier. Two-dimensional near-field and far-field measurements were obtained over a wide range of discharge parameters. The spot size and divergence of the laser beam were observed to increase significantly with decreasing discharge pressure. Simultaneously, the beam intensity distribution changed from a single peak pattern to an annular profile. These effects are shown to be the result of increased refraction of the soft-x-ray beam, caused by larger density gradients in the plasma columns of the lower pressure discharges. The spatial images are nearly cylindrically symmetric, and have less structure than those reported in the literature for laser-driven soft-x-ray lasers. Beam profiles synthesized by model calculations are found to be in good agreement with the recorded images. The obtained images in combination with the model computations clarify the origin of the different beam patterns that are observed in capillary discharge soft-x-ray laser experiments

Applications of high repetition rate tabletop soft X-ray lasers become a reality in several fields

Includes bibliographical references (page 468).For many years researchers have envisioned the development of compact high repetition rate tabletop soft x-ray laser, 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 caprllary discharge pumped 46.9nm laser m 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

Demonstration of a high average power tabletop soft x-ray laser

Includes bibliographical references (page 5807).We report the first demonstration of a high average power tabletop soft x-ray laser. An average laser output power of ≈1 mW (>2 × 1014 photons/s) was generated at 46.9 nm in Ne-like Ar using a very compact tabletop discharge. The spatially coherent average power emitted by this 26.5 eV laser is comparable to that generated at this photon energy in a similar bandwidth (Δλ/λ = 10-4) by a third generation synchrotron beam line. Lasing was obtained at a repetition rate of 7 Hz with an average output energy of 135 μJ/pulse by exciting a plasma column in a ceramic capillary with a fast current pulse. This very compact high-repetition-rate laser source makes intense short-wavelength coherent radiation accessible to a wide variety of new applications