Formation of subwavelength periodic structures on tungsten induced by ultrashort laser pulses

Institute of Optics, Information and Photonics, Max-Planck Research Group and University Erlangen-Nuremberg, 91058 Erlangen, Germany.
Optics Letters (Impact Factor: 3.29). 08/2007; 32(13):1932-4. DOI: 10.1364/OL.32.001932
Source: PubMed


The evolution of surface morphology of tungsten irradiated by single-beam femtosecond laser pulses is investigated. Ripplelike periodic structures have been observed. The period of these ripples does not show a simple relation to the wavelength and angle of incidence. The orientation of ripples is aligned perpendicularly to the direction of polarization for linearly polarized light. Surprisingly, we find that the alignment of the ripple structure turned left or right by 45 degrees with respect to the incident plane when using right and left circularly polarized light, respectively. The period of the ripple can be controlled by the pulse energy, the number of pulses, and the incident angle. We find a clear threshold for the formation as a function of pulse energy and number of pulses. The mechanism for the ripple formation is discussed, as well as potential applications in large-area structuring of metals.

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    • "In the last decade, a number of experimental studies have shown that intense femtosecond (fs) laser pulses produce periodic nanostructures on the surface of solids such as dielectrics [1] [2] [3], semiconductors [4] [5] [6] and metals [7] [8], and also inside transparent materials [9] [10], where the structure size observed is typically 1/10 – 1/5 of the laser wavelength used. Since the nanostructure formation observed for various kinds of solid materials suggests a new field of nanoscale, ultrafast light-matter interaction physics and its potential routes to laser nano-processing beyond the diffraction limit, much attention has been focused on the physical mechanism responsible for nanostructuring induced with fs laser pulses. "
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    ABSTRACT: It is shown that superimposed multiple shots of linearly polarized 800-nm, 100-fs laser pulses at lower fluence than the single-pulse ablation threshold produce periodic nanostructures with almost constant periods of 150 nm and 400 nm on silicon surface immersed in water. The nanostructure formation and its characteristic properties observed are illustrated well with the excitation of surface plasmon polaritons in the newly created surface layer. Pump and probe measurements of surface reflectivity during the ultrafast interaction demonstrate that multiple shots of low-fluence fs pulses are crucial to the accumulation of non-thermal bonding structure change and subsequent ablation for the periodic nanostructure formation.
    Physics Procedia 12/2012; 39:674–682. DOI:10.1016/j.phpro.2012.10.088
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    • "Another interesting direction for future research would be to study the effects of various LIPPS signatures and their orientation. The theory of LIPPS formation is relatively well known (Qi et al. 2009; Zhao et al. 2007) and LIPPS can be controlled with, for example, polarization and the angle of incidence. Wang et al. (2008) generated LIPPS to polystyrene with a p-polarized laser using a wavelength of 266 nm. "
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    ABSTRACT: The purpose of the present study is to explore topographical patterns produced with femtosecond laser pulses as a means of controlling the behaviour of living human cells (U2OS) on stainless steel surfaces and on negative plastic imprints (polycarbonate). The results show that the patterns on both types of material strongly affect cell behaviour and are particularly powerful in controlling cell spreading/elongation, localization and orientation. Analysis by fluorescence and scanning electron microscopy shows that on periodic 1D grating structures, cells and cell nuclei are highly elongated and aligned, whereas on periodic 2D grid structures, cell spreading and shape is affected. The results also show that the density and morphology of the cells can be affected. This was observed particularly on pseudo-periodic, coral-like structures which clearly inhibited cell growth. The results suggest that these patterns could be used in a variety of applications among the fields of clinical research and implant design, as well as in diagnosis and in cell and drug research. Furthermore, this article highlights the noteworthy aspects and the unique strengths of the technique and proposes directions for further research. Electronic supplementary material The online version of this article (doi:10.1007/s10544-012-9726-8) contains supplementary material, which is available to authorized users.
    Biomedical Microdevices 11/2012; 15(2). DOI:10.1007/s10544-012-9726-8 · 2.88 Impact Factor
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    • "At high intensities and broadband excitation as delivered by ultrashort-pulse lasers, the scenario becomes more complex by including multiphoton excitation channels and/or spectral selectivity. As was shown for different types of materials like, for example, Er:BaTiO 3 [16], ZnSe [17], W [18], Si [19], NiTi alloy [20], fused silica glass [21] [22], ZnO [23] [24], sapphire [25], TiN [26] or diamond-like carbon [26], nonlinear excitation with femtosecond laser pulses enables structural periods well below the excitation wavelengths (sub-wavelength LIPSS). For the formation of such nanoscale LIPSS (nanoripples) in dielectric media, two distinct types of structures are observed, which can be described as ablation reliefs (see, e.g., [23]) in the first case and the creation of deep, nearly planar grooves or nanoplanes normal to the surface (compare, e.g., [25]) in the second case. "
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    ABSTRACT: An efficient way to generate nanoscale laser-induced periodic surface structures (LIPSS) in rutile-type TiO(2) with frequency-converted femtosecond laser pulses at wavelengths around 400 nm is reported. Extended-area structuring on fixed and moving substrates was obtained by exploiting the line focus of a cylindrical lens. Under defined conditions with respect to pulse number, pulse energy and scanning velocity, two types of ripple-like LIPSS with high and low spatial frequencies (HSFL, LSFL) with periods in the range of 90 nm and 340 nm, respectively, were formed. In particular, lower numbers of high energetic pulses favour the generation of LSFL whereas higher numbers of lower energetic pulses enable the preferential creation of HSFL. Theoretical calculations on the basis of the Drude model support the assumption that refractive index changes by photo-excited carriers are a major mechanism responsible for LSFL. Furthermore, the appearance of random substructures as small as 30 nm superimposing low spatial frequency ripples is demonstrated and their possible origin is discussed.
    Nanotechnology 03/2010; 21(15):155302. DOI:10.1088/0957-4484/21/15/155302 · 3.82 Impact Factor
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