Huge numbers of 2D- or 3D- nanostructures can be generated by interfering ultra-short pulse laser processing in a single
shot. Unit structures are nanowhiskers, nanoneedle, nanobump, nanomesh of metal. The distribution of these
nanostructures are according to interference pattern, which can be controlled and designed by the number of beams,
correlation angle, amplitude ratio and phase shifts between the beams. In this paper, we simulated the interference
pattern with different combinations of these parameters. Our technique is useful for fabrication of metamaterials, in
which designed unit structures are in designed periodic patterns.
Interfering femtosecond laser can induce periodic induction of energy on a thin film deposited on a substrate, and
periodic thermal process is induced. This results in liquid motion of target, such as melting, inflation, flow and shrink,
and then it freezes due to temperature fall by thermal radiation and conduction. The resultant structures are nanobump,
nano-whisker, nano-waterdrop, nano-crown, and the shapes can be controlled by laser fluence, thin film thickness,
substrate material, etc.. The size of some structures is smaller than 10 nm in curvature radius, and the aspect ratio is over
20. In addition, duplicated structure of two shapes, or double density structures can be generated in a single shot of laser
irradiation by controlling the phase shift and power ratio between interfering beams. In the case of duplicated structure,
the density of nano-structures is doubled, and two different nano-structures appear alternately. These structures will be
useful in nanotechnology, especially in meta-material technology.
Interfering ultra-short pulse laser processing can make nano-structures on metallic thin films. The unit nano-structures
are nano-waterdrop, nanocrown, nanobump etc.. They change according to the character of target and the interference
pattern. An interference pattern of four beams, diffracted by a transmission grating, is like a simple matrix. We generated
arranged periodic structures different from the past experiments, by changing the configuration of four interfering beams.
Parameters of an interference pattern are wavelength, correlation angle, difference of intensities and phase shift between
the beams. As a result, complicated or duplicated structures can be generated.
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