The strong absorption of light [ 1 ] and the local amplifi cation of the electromagnetic fi eld [ 2 ] at the plasmon resonance of noble metal nanostructures have been the focus of hundreds of studies due to their practical applications for the fabrication of optical devices such as fi lters, non-linear optical components, or Raman enhancers. [ 3,4 ] The control of the plasmon features such as spectral width, [ 5 ] position, [ 6 ] and shape [ 7 ] can be accomplished by different physical deposition routes [8][9][10][11][12] providing adequate growing conditions of metal nanoparticles (MNPs). Pioneer works in the 1990s showed the optical selectivity of elongated Ag deposits on SiO 2 with applications as optical fi lters for windows to control solar heat gain and glare, among others. [ 13 ] Recently, assemblies of parallel stripes of MNPs have been fabricated onto preformed surfaces presenting a 1D periodic roughness [ 14 , 15 ] or bundled SiO 2 nanocolumns. [ 16 , 17 ] A signifi cant macroscopic optical dichroism has been reported for these systems that can be useful for the development of polarized light emitters or materials with an enhanced IR luminescence because of the excitation of two distinct plasmon resonances in the directions parallel (longitudinal mode) and perpendicular (transverse mode) to the stripes. [ 18 ] Architecture control of the metal assemblies plays a determinant role in the functional properties of the material. For this purpose, the softlithographic techniques provide means to accurately tailor the nanostructure of the materials. [18][19][20][21] Laser scanning is a softlithographic technique widely used to modify the shape and structure of metal nanoparticles. [21][22][23][24] Surface modifi cation can be easily achieved by in situ [ 21 ] or ex situ [22][23][24] pulsed laser treatment in the case of random systems of MNPs. In contrast, nothing has been reported about the effect of a pulsed laser on the structure and optical dichroism of autoorganized metal nanostructures. In this paper we show that nanosecond (ns) laser irradiation can be effectively used to control the optical dichroism of Ag stripes supported on SiO 2 nanocolumns (NCs). This dichroism can be effectively tailored along the full visible range. Thus, we propose the utilization of the AgNPs/SiO 2 NCs structures for writing dichroic patterns at the microscale with potential applications for encryption and data storage purposes.AgNPs/SiO 2 NCs fi lms were grown by a two-step process.[ 17 ]First, SiO 2 thin fi lms were deposited by glancing angle vapor deposition (GLAD) with a tilted columnar nanostructure and ≈ 350 nm thickness (see Figure S1a in the Supporting Information and the Experimental Section). [ 25 , 26 ] These structures present an anisotropic surface topography known as "bundling", [ 17 ] consisting of the coalescence of the NCs along the x -direction ( Figure S1b). The silver nanoparticles were then grown by DC sputtering at room temperature. The "bundled" SiO 2 NCs act as a template for the fabrication of Ag...

We report on the fabrication of laser-induced periodic surface structures in Cr films upon high repetition rate fs laser irradiation (up to 1 MHz, 500 fs, 1030 nm), employing beam scanning. Highly regular large-area (9  cm2) gratings with a relative diffraction efficiency of 42% can be produced within less than 6 min. The ripple period at moderate and high fluences is 0.9 μm, with a small period of 0.5 μm appearing at lower energies. The role of the irradiation parameters on the characteristics of the laser-induced periodic surface structures (LIPSS) is studied and discussed in the frame of the models presently used. We have identified the polarization vector orientation with respect to the scan direction as a key parameter for the fabrication of high-quality, large-area LIPSS, which, for perpendicular orientation, allows the coherent extension of the sub-wavelength structure over macroscopic distances. The processing strategy is robust in terms of broad parameter windows and applicable to other materials featuring LIPSS.

Highlights Laser ablation incubation at air is controlled by thermal properties of the metal.  Incubation in liquid contact is determined by the mechanical impact on the solid material by the bubble cavitation and the ultimate tensile stress of the metal. AbstractIncubation effects in the nanosecond laser ablation of metals exhibit a strong dependence on the thermal and mechanical properties of both the target material and the background gas or liquid. The incubation in air is controlled mainly by thermal properties such as the heat of vaporization. In liquid, the correlation of the incubation and the ultimate tensile stress of the metals suggests that incubation may be related to the mechanical impact on the solid material by the cavitation bubble collapse, causing accumulation of voids and cracks in the subsurface region of the ablation craters. At high ultimate tensile stress, however, the low sensitivity to the environment suggests that the mechanical impact is likely to play a negligible role in the incubation. Finally, the correlation between the incubation and the carbon content of alcoholic liquids may be explained by an absorptivity increase of the cavity surfaces due to carbonaceous deposits generated by laser-induced pyrolysis, or by the mechanical impact of long-living bubbles at higher dynamic viscosity of liquids.

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