High speed inscription of uniform, large-area laser-induced periodic surface structures in Cr films using a high repetition rate fs laser

Abstract

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.

LIPSS on thin metallic films: New insights from multiplicity of laser-excited electromagnetic modes and efficiency of metal oxidation

“…8 (low oxidation side) for a pure or slightly oxidized metal film, the branches of the SEW modes (-,+), (+,-) and (+,+) could be a responsible explanation for the HSFL formation if to assume that the periodicities of these modes are decreasing as a result of laser action. However, the phenomenon of multi-pulsed ultrashort laser 18 irradiation of matter is an intricate phenomenon, which involves numerous processes and calls for further studies.…”

Triangular laser-induced submicron textures for functionalising stainless steel surfaces

“…Such large-area texturing has been investigated by employing different processing strategies, e.g. the use of moving discrete spot laser irradiation to merge LIPSS [25,26] or through pulse overlapping [18,[27][28][29][30]. High repetition rates combined with high scanning speed, in the order of MHz and m/s respectively, has also been shown to enable area processing with sufficient pulse fluence and pulse overlap to generate uniform LIPSS in one pass; the uniformity being then obtained by optimising the distance between scanned lines [29].…”

“…the use of moving discrete spot laser irradiation to merge LIPSS [25,26] or through pulse overlapping [18,[27][28][29][30]. High repetition rates combined with high scanning speed, in the order of MHz and m/s respectively, has also been shown to enable area processing with sufficient pulse fluence and pulse overlap to generate uniform LIPSS in one pass; the uniformity being then obtained by optimising the distance between scanned lines [29]. However, potential local non-uniformities of LIPSS are known to occur as a result of preceding polishing step [28,31], grain boundaries [32] and surface defects [28].…”

Growth of ZnO nanostructures by femtosecond laser irradiation of polycrystalline targets

“…The spot diameter at the sample surface was determined to be 80 lm (1/e 2 intensity) by means of a laser beam profilometer (Wincam D). The F-Theta lens ensured flat-field focusing and a displacement linear with the deflected beam angle [19]. In the irradiation set B, the laser is static while in the irradiation set C is scanned over the sample surface.…”

“…The subsequent work by Sipe and coworkers [6,7] provided the initial basis for the comprehension of their formation mechanism. These periodic structures occur in all types of materials [8] and the details regarding their formation mechanism with respect to the specific material, and processing conditions are still a very active field of research [1,[9][10][11][12][13][14][15][16][17][18][19]. Two different kinds of LIPSS are usually observed in most materials: low and high spatial frequency LIPSS (LSFL and HSFL, respectively), with periods K of the order of the incident wavelength for LSFL or much smaller, typically K/4-K/6, for the HSFL.…”