By this method many kinds of materials have been processed or modified. The earliest laser Choosing 
interference structuring can be dated back to 1987 by lcisin!¥; interference pattern was used the material 
to ablate sub-micrometer periodical gratings in polyimide. Later in 1992, Phillips! used a i.e., evapor: 
holographic arrangement to generate electrical conduction wires with nanometer size. In 1998 etc. 
Fukumural® has used laser interference pattern for spatially selective laser molecular 
implantation with poly(butyl methacrylate) PMMA. Stutzmann'®! and Nebel!® have 
investigated nano structures produced by two and three interfering beams to generate 
polycrystalline silicon lines in amorphous silicon film and two dimensional pc-Si seed array 
for subsequent thermal growth of large crystallites respectively. In 1999 Lippert!’ using laser Ee 
ablation as single step dry etching of specially designed polymers, created an optical grating Beam dung 
with variable modulation efficiency. In 2000 Satoru!®! produced 3D photonic crystal structures aa 
with photopolymerizable resin by multi-beam laser interference. I 
In our research‘! we have put emphasis on the dependence of the feature form and size on _—— 
the energy density, beams configuration, and the underlying physical mechanism as well. In 
this paper we present at first the principle of the nano-microstructuring, including 77 A 
experimental set up and the simulation of laser interference patterns, followed by results of u 
structuring on crystalline silicon(c-Si), ceramic(ALO3), gold(Au) film on plastics PMMA, and — 
hydrogen aluminum oxygen(HAIO) film on copper. U 
CHE 
2.Principle of the micro-structuring | 
For the micro-structuring one needs two or more coherent laser beams to define special Sa te 
patterns through laser interference, by varying laser parameter and the geometrical _ 
configuration. These are shown in the experimental set up, and described by computer 
simulation under the assumption of plane-wave approximation. 
2.1 Experimental setup Figure 1 E 
configuratio 
The whole system is shown in figure 1. High power Nd:YAG pulsed laser is selected due to | 
its high pulse power and short wavelengths, produced by the frequency mixing in a non-linear 2.2 Laser i 
crystal. 
The laser bear is then divided into two, three or more partial beams through splitters, and Under the 
then combined again by mirrors on the surface of the sample, where they make interference by the supe 
and form a definite energy distribution, which will be immediately transformed to the surface as example 
of the material. 
To reduce influences from the optical elements, high flatness of the splitters and mirrors is | 
needed to consist the whole system. Moreover in order to get interference patterns E= er 
corresponding to a wide range of optical-way-difference, the laser is operated with an 
enhanced coherence(coherent length of at least 1 meter) under the excitation of a seed. By the HE? =[c 
combination of a polarizer and a half-wave plate one can adjust the energy level impinged on 
the sample. The energy level can also be adjusted by a mechanical shutter to choose the 
number of pulses; by a two-lens consisted telescope one can change the diameter of the laser 
beam and therefore the energy density received on the sample surface. By changing 
wavelength A of the laser beam, and the including angles among the partial beams, one can We have st 
change the period P of the structure according to form, and t 
p= A , total intensi 
= sno | individual t 
where 0 is half of the including angel among the partial beams. and 36 time 
localised in 
(1 
30