Analytical probes capable of mapping molecular composition at the nanoscale are of critical importance to materials research, biology and medicine. Mass spectral imaging makes it possible to visualize the spatial organization of multiple molecular components at a sample's surface. However, it is challenging for mass spectral imaging to map molecular composition in three dimensions (3D) with submicron resolution. Here we describe a mass spectral imaging method that exploits the high 3D localization of absorbed extreme ultraviolet laser light and its fundamentally distinct interaction with matter to determine molecular composition from a volume as small as 50 zl in a single laser shot. Molecular imaging with a lateral resolution of 75 nm and a depth resolution of 20 nm is demonstrated. These results open opportunities to visualize chemical composition and chemical changes in 3D at the nanoscale.
Efficient excitation of dense plasma columns at 100-Hz repetition rate using a tailored pump pulse profile produced a tabletop soft-x-ray laser average power of 0.1 mW at λ = 13.9 nm and 20 μW at λ = 11.9 nm from transitions of Ni-like Ag and Ni-like Sn, respectively. Lasing on several other transitions with wavelengths between 10.9 and 14.7 nm was also obtained using 0.9-J pump pulses of 5-ps duration from a compact diode-pumped chirped pulse amplification Yb:YAG laser. Hydrodynamic and atomic plasma simulations show that the pump pulse profile, consisting of a nanosecond ramp followed by two peaks of picosecond duration, creates a plasma with an increased density of Ni-like ions at the time of peak temperature that results in a larger gain coefficient over a temporally and spatially enlarged space leading to a threefold increase in the soft-x-ray laser output pulse energy. The high average power of these compact soft-x-ray lasers will enable applications requiring high photon flux. These results open the path to milliwatt-average-power tabletop soft-x-ray lasers.
We have demonstrated the efficient generation of sub-9-nm-wavelength picosecond laser pulses of microjoule energy at 1-Hz repetition rate with a tabletop laser. Gain-saturated lasing was obtained at ¼ 8:85 nm in nickel-like lanthanum ions excited by collisional electron-impact excitation in a precreated plasma column heated by a picosecond optical laser pulse of 4-J energy. Furthermore, isoelectronic scaling along the lanthanide series resulted in lasing at wavelengths as short as ¼ 7:36 nm. Simulations show that the collisionally broadened atomic transitions in these dense plasmas can support the amplification of subpicosecond soft-x-ray laser pulses. DOI: 10.1103/PhysRevX.1.021023 Subject Areas: Photonics, Plasma PhysicsThe high demand for bright soft-x-ray laser (SXRL) pulses greatly exceeds the beam time available at a few single-user free-electron laser facilities [1,2]. This motivates the development of more compact and widely accessible SXRLs for a broad range of experiments in small laboratory settings. Significant progress has been achieved in the past few years in the development of compact plasma-based soft-x-ray lasers [3][4][5][6][7][8][9][10]. However, repetitive operation of tabletop SXRLs has been limited to wavelengths above 10.9 nm [10]. At shorter wavelengths, the large pump energy required has limited the repetition rate to typically one shot per hour [11][12][13][14][15]. Soft-x-ray lasing at sub-10-nm wavelengths in lanthanide ions was first demonstrated using optical lasers of pump energy of several hundred joules [12,13]. Lasing in nickel-like lanthanum at ¼ 8:85 nm was later obtained by using 18-J pulses from a chirped-pulse-amplification (CPA) laser to achieve transient excitation, but with a gain-length product (g  l ¼ 7:7) that remained insufficient to reach gain saturation [15]. Progress toward saturated lasing in this transition has been recently reported [16,17]. In turn, lasing at ¼ 7:36 nm in nickel-like Sm was initially demonstrated using 130-J pump pulses [12]. Later, gain saturation was reached using a picosecond-duration pump pulse with approximately 40 J of energy added to a prepulse of similar energy [14]. Also recently, the lasing threshold in this line was reached through the use of a total optical pump energy of 36 J [18]. However, the practical realization of highrepetition-rate tabletop lasers at sub-10-nm wavelengths requires obtaining gain-saturated lasing at significantly lower pump energies. We report the generation of gainsaturated picosecond SXRL pulses at ¼ 8:85 nm at 1-Hz repetition rate. The result is obtained by using a picosecond pump pulse with an unprecedentedly low energy of 4 J and a total optical pump energy of 7.5 J, that will make the operation at high-repetition rates possible. Furthermore, using the same pump energy, we observe lasing at wavelengths down to ¼ 7:36 nm in transitions of higher-Z nickel-like lanthanide ions, opening the prospect of practical gain-saturated tabletop lasers at shorter wavelengths. Modeling suggests that these dense-pl...
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