Laser energy absorption and x-ray generation in nanowire arrays irradiated byrelativistically intense ultra-high contrast femtosecond laser pulses

We report here on the results of comparative experimental measurements of laser energyabsorption in a bulk and different morphology nanowire arrays interacting withrelativistically intense, ultra-high temporal contrast femtosecond laser pulses. Wecompare polished, flat bulk samples with vertically a...

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Bibliographic Details
Published in:Physics of plasmas 2022-01, Vol.29 (1)
Main Authors: Blümcke, M S, Samsonova, Z, Zapf, M
Format: Article
Language:English
Subjects:
Arrays
Bulk sampling
Emission analysis
Energy absorption
Femtosecond pulses
Lasers
Mathematical models
Morphology
Nanowires
Plasma physics
Resonance lines
Semiconductor materials
Spectrum analysis
Zinc oxide
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Summary:We report here on the results of comparative experimental measurements of laser energyabsorption in a bulk and different morphology nanowire arrays interacting withrelativistically intense, ultra-high temporal contrast femtosecond laser pulses. Wecompare polished, flat bulk samples with vertically and randomly oriented nanowires madeof ZnO semiconductor material. The optical absorption of the 45° incident laser pulses of∼40 fs duration with a central wavelength of 400 nm at intensities above 1019Wcm2was determined using an integrating Ulbricht sphere. We demonstrate an almost twofoldenhancement of absorption in both nanowire morphologies with an average of (79.6±1.9)% in comparison to the flat bulksample of (45.8±1.9)%. The observed substantiallyenhanced absorption in nanowire arrays is also confirmed by high-resolution x-ray emissionspectroscopy. The spectral analysis of the K-shell x-ray emission lines revealed that theHe-like resonance line emission from highly ionized Zn (Zn28+) is only presentin the case of nanowire arrays, whereas, for the flat bulk samples, only neutral and lowcharge states were observed. Our numerical simulations, based on radiative-collisionalkinetic code FLYCHK, well reproduce the measured He-like emission spectrum and suggestthat high charge state observed in nanowire arrays is due to substantially higher plasmatemperature. Our results, which were measured for the first time with femtosecond laserpulses, can be used to benchmark theoretical models and numerical codes for therelativistic interaction of ultrashort laser pulses with nanowires.
ISSN:1070-664X
1089-7674