FOCUS
MANUFACTURING with short pulse lasers
the focussed laser beam spot sizes exceed the desired size of the laser-induced nanostructures by orders of magnitude. However, here intra-pulse coherent scattering and near-field interference effects emerging in the laser-irradiated area / volume can seed periodic nanoscale patterns of the absorbed optical energy. The latter are subsequently transferred to the lattice of the solid and eventually imprinted as a corrugated surface topography or in sub-ablative periodic volume modifications. These two scenarios of LIN are demonstrated in the lower part of Figure 2. The left panel( Fig. 2( c)) collects SEM images of several different types of so-called Laser-Induced Periodic Surface Structures( LIPSS). They are classified as Low Spatial Frequency LIPSS( LSFL), Triangular
Nano-Pillars( TNP), or Hexagonally- Arranged Nanostructures( HAN) – all with spatial periods close to λ, or as High Spatial Frequency LIPSS( HSFL) having periods down to the tens to hundreds of nm range, i. e., far below the optical diffraction limit [ 1,7 ]. HSFL are solely formed upon irradiation with UPLs. The right panel( Fig. 2( d)) assembles results from
Figure 2. Selected LIN results and their methodic categorization into surface and volume processing( columns), while using direct focussing or selfordering effects( rows). Figure 2( a) I( bottom) reprinted from [ 3 ] Copyright( 2004) National Academy of Sciences, U. S. A.; Figure 2( a) II( top and bottom right) reprinted from [ 4 ] Copyright 2023 under Creative Commons BY-NC-ND 4.0 license, and with permission from the authors of that article( F. Courvoisier.); Figure 2( b) I( bottom) reprinted with permission from [ S. Juodkazis et al., Phys. Rev. Lett., 96, 166101, 2006 ] Copyright( 2006) by the American Physical Society.; Figure 2( b) II reprinted with permission from [ 6 ]. Copyright 2019 American Chemical Society; Figure 2( c) I reprinted from [ S. V. Kirner, et al., J. Appl. Phys. 122, 104901( 2017), with the permission of AIP Publishing; Figure 2( c) II( top) reprinted from [ S. van der Poel, et al., Lubricants 7, 70( 2019)] Copyright 2019 under Creative Commons BY 4.0 license; Figure 2( c) II( bottom) adapted from [ L. Porta-Velilla, et al., Nanomaterials 12, 2380( 2022)] Copyright 2022 under Creative Commons BY 4.0 license; Figure 2( d) I reprinted with permission from [ 8 ]. Copyright 2017 American Chemical Society; Figure 2( d) II used with permission of Royal Society of Chemistry from [ Mater. Horiz., N. Sharma et al., 6, 978-983, 2019 ]; permission conveyed through Copyright Clearance Center, Inc.
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