Characterization of angularly resolved EUV emission from 2-μm-wavelength laser-driven Sn plasmas using preformed liquid disk targets

R. Schupp, L. Behnke, Z. Bouza, Z. Mazzotta, Y. Mostafa, A. Lassise, L. Poirier, J. Sheil, M. Bayraktar, W. Ubachs, R. Hoekstra, O. O. Versolato*

*Bijbehorende auteur voor dit werk

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The emission properties of tin plasmas, produced by the irradiation of preformed liquid tin targets by several-ns-long 2 μm-wavelength laser pulses, are studied in the extreme ultraviolet (EUV) regime. In a two-pulse scheme, a pre-pulse laser is first used to deform tin microdroplets into thin, extended disks before the main (2 μm) pulse creates the EUV-emitting plasma. Irradiating 30- to 300 μm-diameter targets with 2 μm laser pulses, we find that the efficiency in creating EUV light around 13.5 nm follows the fraction of laser light that overlaps with the target. Next, the effects of a change in 2 μm drive laser intensity (0.6-1.8×1011 W cm-2) and pulse duration (3.7-7.4 ns) are studied. It is found that the angular dependence of the emission of light within a 2% bandwidth around 13.5 nm and within the backward 2π hemisphere around the incoming laser beam is almost independent of intensity and duration of the 2 μm drive laser. With increasing target diameter, the emission in this 2% bandwidth becomes increasingly anisotropic, with a greater fraction of light being emitted into the hemisphere of the incoming laser beam. For direct comparison, a similar set of experiments is performed with a 1 μm-wavelength drive laser. Emission spectra, recorded in a 5.5-25.5 nm wavelength range, show significant self-absorption of light around 13.5 nm in the 1 μm case, while in the 2 μm case only an opacity-related broadening of the spectral feature at 13.5 nm is observed. This work demonstrates the enhanced capabilities and performance of 2 μm-driven plasmas produced from disk targets when compared to 1 μm-driven plasmas, providing strong motivation for the use of 2 μm lasers as drive lasers in future high-power sources of EUV light.

Originele taal-2English
Aantal pagina's12
TijdschriftJournal of Physics D: Applied Physics
Nummer van het tijdschrift36
StatusPublished - sep-2021

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