Table-top Soft X-Ray Lasers

Abstract

This article reviews the progress in the development of practical table-top sources of soft x-ray laser radiation. The field is rapidly approaching the stage at which soft x-ray lasers sufficiently compact to fit onto a normal optical table will be routinely utilized in science and technology. This is the result of recent advances in the amplification of soft x-ray radiation in both compact laser-pumped and discharge-pumped devices. The use of excitation mechanisms that take full advantage of new ultrafast high power optical laser drivers and multiple pulse excitation schemes has resulted in the demonstration of saturated soft x-ray amplification at wavelengths as short as 14 nm using several Joule of laser-pump energy. Moreover, several schemes have demonstrated significant gain with only a fraction of a Joule of laser-pump energy. In addition, the demonstration of saturated table-top soft x-ray lasers pumped by very compact capillary discharges has shattered the notion that discharge-created plasmas are insufficiently uniform to allow for soft x-ray amplification, opening a route for the development of efficient, high average power soft x-ray lasers. Recently, a table-top capillary discharge laser operating at 46.9 nm has produced millijoule-level laser pulses at a repetition rate of several Hz, with a corresponding spatially coherent average power per unit bandwidth comparable to that of a beam line at a third generation synchrotron facility. This review summarizes fundamental and technical aspects of table-top soft x-ray lasers based on the generation of population inversions in plasmas, and discusses the present status of development of specific laser systems.

Diagnostics of warm dense matter by high-resolution X-ray spectroscopy of hollow ions

“…This limitation is not important only for super short laser pulses (femtosecond or sub-picosecond) and for short wavelength lasers (vacuum-ultraviolet-or X-ray). Therefore, until now, hollow ion spectra were observed practically only in the femtosecond laser-produced plasma in the cases when laser did not produce preplasma due to the rather low laser intensity (Gauthier et al, 1995) or due to very high (above 10 9 ) laser contrast (see, for example, Faenov et al, 1997;1999;Urnov et al, 1998;Rosmej et al, 2000;Colgan et al, 2008;Skobelev et al, 2012). For longer laser pulse, hollow ion spectra have been observed where short wavelength eximer XeCl-laser or 2w of Nd laser were used (Abdallah et al, 2000;Colgan et al, 2008a;Colgan 2010).…”

“…For such type of spectra, the main resonance lines have low intensities and are practically unresolved. This new type of spectra (Faenov et al, 1997;1999;Urnov et al, 1998;Maksimchuk et al, 2000) is caused by radiation transitions in the multi-charged K 2 -hollow ions, i.e., ions with a completely empty K-shell (see Fig. 1; for more details, see Skobelev et al, 2012).…”

“…Faenov et al 28 matter, the absorption of X-ray radiation directly causes the formation of hollow ions. Currently, the process of hollow ion production by X-ray radiation is becoming more topical in connection with the advent of high-power X-ray lasers, both plasma-based (Elton, 1990;Rocca, 1999;Daido, 2002;Suckewer & Jaegle, 2009) and free-electron lasers (Emma et al, 2010;Vinko et al, 2012;Mimura et al, 2014). With such lasers, the energy input process, unlike that in the case of interaction of optical laser radiation with matter, is directly related to hollow ion production.…”

An extreme ultraviolet interferometer suitable to generate dense interference pattern

“…As sources for interference lithography there are usually used synchrotrons with undulators (tuneable, but with limited coherence) and laser-or discharge-pumped EUV/soft X-ray lasers 17,18 .…”

Nonlinear increase of X-ray intensities from thin foils irradiated with a 200 TW femtosecond laser

“…There are number of platforms for the creation of extremely bright and short X-ray beams 1 necessary for biological imaging 2 , for material processing 3 4 5 6 , for general physics such as laboratory astrophysics 7 8 9 10 11 12 , studies of high energy density plasma 13 14 and exotic states of matter 15 16 17 . The list of powerful X-ray sources has increased in recent years to include transient-collisional plasma X-ray lasers 18 19 , powerful X-ray free-electron-laser sources (XFELs) 15 20 21 , high order harmonics from plasma 22 23 24 25 , Compton scattering extending X-ray energies into sub-MeV range 26 27 28 , and coherent synchrotron radiation including table-top laser systems 29 30 31 . Recently it was proposed that radiation from the dense plasma generated by Petawatt-class laser femtosecond pulses incident on thin-foil targets could be used to explore the radiation dominant kinetic regime (RDKR) 17 .…”