Poster
Reference
Filament Induced Laser Machining
KISELEV, Denis, WOLF, Jean-Pierre, WOESTE, Ludger
KISELEV, Denis, WOLF, Jean-Pierre, WOESTE, Ludger. Filament Induced Laser Machining. In:
COFIL 2010, Crete (Grece), 2010
Available at:
http://archive-ouverte.unige.ch/unige:21868
Disclaimer: layout of this document may differ from the published version.
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Experiment
x
y
z
High power
femtosecond laser
Focusing lens
Focal distance 1 - 4 m Sample
Light filament
Length 10 - 40 cm
Experimental set-up
0 0.2 0.4 0.6 0.8 1 1.2
0 2 4 6 8 10 12 14 16
Pulse energy, mJ
Plasma channel length, cm
Filament length versus pulse energy
0 0.5 1 1.5 2 2.5
5 6 7 8 9 10 11 12 13 14 15 16
Pulse duration, ps
Plasma channel length, cm
Negative chirp Shortest pulse Positive chirp
Filament length versus pulse duration
Introduction Results
References
Simultenius LIBS signal observation
350 400 450 500 550 600 650
0 0.5
1 Aluminium
Wavelength, nm
Relative intensity
350 400 450 500 550 600 650
0 0.5
1 Stainless steel
Wavelength, nm
Relative intensity
350 400 450 500 550 600 650
0 0.5
1 Brass
Wavelength, nm
Relative intensity
Ludger Wöste
Institut für Experimentalphysik Freien Universität Berlin
Denis Kiselev, Jean-Pierre Wolf
Département de Physique Appliquée Université de Genève
Filament Induced Laser Machining
Fonds national suisse
de la recherche scientifique
103 104 105 106 107
Distance from the lens to the working point, mm
Number of shots to drill a hole
Aluminium Brass
Stainless steel
980 1000 1020 1040 1060 1080 1100 1120 1140 1160 100
101 102 103 104
Processing time, s
100 μm 100 μm 100 μm
Stainless steel Aluminium Brass
Hole drilling in metals
Cutting complex metal shapes
High power ( > 3 GW in air) ultrafast laser pulses can propagate in transparent medium in a non-linear regime called filamentation based dynamic balance be- tween Kerr-focusing and self generated plasma defocusing. Filaments have rela- tively small size (hundreds of micrometers) on large distances (from a few cen- timeters to hundreds of meter).
These properties make filaments an attractive tool for the laser machining with- out focusing on the sample surface and without need to follow the sample shape.
This study shows the potential of filaments in laser metal cutting and hole drill- ing in metals and also for biological material sawing.
The 1.2 W, 120 fs laser pulses are focused by a lens (F=1 - 4 m). The sample is placed in the filament region on a translation stage. This region length
varies with the focal length. The linear Rayleigh limit (2Zr) is 10 mm for a one meter focal length and 80 mm for a fourth meter focal length.
The experiment aims to use the filaments for high aspect ratio metal hole drilling. Three sample metals with nominal thickness 0.5 mm were drilled through in different positions of the filament.
Plasma is measured at the range of 1000 mm to 1150 mm from the fo- cusing lens.
Scanning electron microscope images of holes drilled in different metals.
Typical hole diameter is 50 - 100 um. Maximal aspect ration is 1:20.
The characteristic plasma lines and black body radiation are observed during the machining. LIBS can be used to monitor temperature and material composition.
(a) (b)
(c) (d)
The objects with complex shapes and thick walls (0.1 - 0.3 mm) are usually difficult to processe mechanically.
We demonstrate that filaments can cut such objects in 10 - 20 minutes.
(a) Initial aluminium can ; (b) Cut profile ;
(c) Window cutting in a can; (d) Result of the window cutting
Biological material sawing
(b)(c) (d)
(c) (b)
(a) (d)
(a) Meat sawing; (b) Result of the meat sawing ; (c) Bound cutting; (d) Result of the bound cutting Biological matirials can also be processed.
Typical cutting time ranges from 10 to 20 minutes for a on centimeter thick meat or bone sample.
Conclusions
This study shows that light filaments can be successfully used in laser machining.
The high aspect ratio (1:20) drilling in metals gives fixed hole diameter (50-100 um). The hole surface quality and the shape depend on the laser spatial profile and can be potentially optimized in further experiments.
The complex metal shapes are cut properly and without technical difficulties such as adaptive laser focusing or laser shots and sample movement synchronization.
The plasma lines monitoring during the machining gives supplementary information about the material composition. The black body radiation can give an estimation of the sample temperature in the working point.
The biological materials can be also treated. By microscopic observations, filament machining does not leave any strong burns.
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