Compact gain-saturated x-ray lasers down to 685  nm and amplification down to 585  nm

Abstract

Plasma-based x-ray lasers allow single-shot nano-scale imaging and other experiments requiring a large number of photons per pulse to be conducted in compact facilities. However, compact repetitively fired gain-saturated x-ray lasers have been limited to wavelengths above λ 8.85 nm. Here we extend their range to λ 6.85 nm by transient traveling wave excitation of Ni-like Gd ions in a plasma created with an optimized pre-pulse followed by rapid heating with an intense sub-picosecond pump pulse. Isoelectronic scaling also produced strong lasing at 6.67 nm and 6.11 nm in Ni-like Tb and amplification at 6.41 nm and 5.85 nm in Ni-like Dy. This scaling to shorter wavelengths was obtained by progressively increasing the pump pulse grazing incidence angle to access increased plasma densities. We experimentally demonstrate that the optimum grazing incidence angle increases linearly with atomic number from 17 deg for Z 42 (Mo) to 43 deg for Z 66 (Dy). The results will enable applications of sub-7 nm lasers at compact facilities.

Amplification of Elliptically Polarized Sub-Femtosecond Pulses in Neon-Like X-Ray Laser Modulated By An IR Field

“…Besides, due to the similarity of the energy structure of nickel-like and neon-like ions, this method can also be applied to the case of nickel-like active media (in particular, those based on Mo 14+ , Ag 19+ or Kr 8+ ions). In prospect, this opens up the possibility of amplifying the radiation of harmonics of elliptical and circular polarization in shorter-wavelength spectral ranges [38]. To the best of our knowledge, this is the first approach which suggests the amplification of sub-femtosecond pulses of XUV radiation with arbitrary elliptical polarization.…”

A brief history of short wavelength coherent radiation sources

“…This allowed lasing at short wavelengths with pumping from high rep rate optical lasers of duration several picoseconds with energy less than one Joule per pulse: conditions enabling table-top short wavelength laser action. 20,21,22 Capillary lasers were also developed where a sequence of electrical discharges through argon contained in a narrow ceramic capillary produces the necessary plasma energy density and electron collisional pumping to produce lasing at 46.9 nm in neon-like argon. 23,24 Optical field ionization using circularly polarized laser light incident into a gas or pre-formed plasma has also produced electron collisionally pumped lasing at similar wavelengths, for example, 32.8 nm in nickel-like krypton.…”

“…The development of grazing-incidence pumping has enabled soft-x-ray lasing down to Ni-like Dy at 5.86 nm to be observed with pumping from optical laser pulses of energy ≈ 1 − 10 Joule. 21,22…”

Biological laboratory x-ray microscopy

“…A number of different techniques can be used to produce high-brightness coherent illumination on a laboratory scale. These include high harmonic generation (HHG) [91,92], plasma-based x-ray lasers (XRL) [93,94] and various techniques based on laser-wakefield accelerators (LWFA) [95]. Microscopic imaging in the EUV [92,96] and hard x-ray regime [95] has been demonstrated.…”