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HOCHSCHULEAACHEN

U:\PC_WNDWS\VORLAGEN\LLT_1.pot

Laser Applications R&D at FraunhoferInstitute for Laser Technology

Jens Gottmann, Claudia Hartmann, Alexander Horn,Leonid Moiseev, Lena Trippe

Fraunhofer Institut fr Lasertechnik &

Lehrstuhl fr Lasertechnik

der RWTH-AachenSteinbachstrasse 15

52074 Aachen

Germany

[email protected]

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P:/A33/Geraete/Anschaffung/Umzug_fs_Anwendung.ppt

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LEHRSTUHL FR LASERTECHNIK

RHEINISCH-WESTFLISCHETECHNISCHEHOCHSCHULE

AACHEN

Outline

The Fraunhofer Institute for Laser Technology

Related Results & Planned Experiments at JLAB FEL

Micro-ablation with tailored pulse trains Drilling with s-laser radiation

PLD

Conclusion

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Tailored Optical Energy

Manufacturing

- Processes

- System technology

Microelectronics (EUV)

Life science

- Biophotonics

- Biocompatible

Materials

Atomic and molecular

Lasers

Power/ Energy

Quality

- space (focusability)

- time (pulse durationand formation)

- spectral (wavelength,

Laser types)

1 m

20 cm

150 nm

Application

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Vertical Structure: Car body welding with a high power DPSSL

High-powerdiode-laser chips andpackaging Lifetime

Systems design:high efficiency and

beam quality

Dr.Ing. H.c. F.Porsche AG

Weldingprocess andmaterialsscience

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Organisation of Fraunhofer-ILT and of LLT RWTH Aachen University

Plasma and X-Ray

LLTDr. E. W. Kreutz

Dr. J. Gottmann

Prof. Dr. R. PopraweVice Director

Administration

ILTDr. P. Loosen

B. Grossmann

Beam Sources Laser Applications

Integrated Optics

Beam Sources

Metrology andSurface Analysis

Laser ComponentsDr. K. Boucke

Solid State/Diode LasersD. Hoffmann

MetrologyDr. R. Noll

Plasma TechnologyDr. W. Neff

CLT PlymouthDr. S. Heinemann

CLFA ParisDr. W. Knapp

Joining and CuttingDr. D. Petring

Surface TechnologyDr. K. Wissenbach

Micro TechnologyDr. A. Gillner

System IntegrationDr. S. Kaierle

Surface Technology

Micro StructuringThin Film Technology

System Integration

Modelling and Simulation Dr. W. Schulz

Marketing andCommunication

A. Bauer

Quality ManagementDr. A. DrenkerM. Talkenberg

IT-ManagementDr. B. Weikl

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Planned Experiments atJLAB FEL

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Motivation

Industry needs e.g. drillings and microstructures

more reproducible

faster production

higher quality (e.g. melt-free)

Development

of anapplication-

adapted lasersystem

Solution new laser system

high-power

high repetition rate

ultra-short pulse duration

Challenge plasma formation

interaction of laser radiation with plasma

Use a FEL

Variation of

repetition rate

wave length

pulse duration

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Related Results & planned Experiments

Micro-ablation with tailored pulse trains

Drilling with s-laser radiation

PLD

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Micro-ablation with tailored pulse trains

Claudia Hartmann

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Micro-ablation with laser radiation

aim

expansion of process limits during micro-ablation of metal (1064 nm)

less melt on the surface high ablation rates

use of tailored pulse trains

interdepartmental cooperation of corecompetence teams of ILT/LLT

process know-how laser techniques

system technology modelling and simulation

state of the art

micro-ablation with femtosecond -microsecond pulses

materials: metals and ceramics 2.5 dimensional structures 355 nm - 1064 nm (depending on

material)

Used Laser for Project at ILT/LLT

pulse duration 15 ns to 50 ns burst energy 2 mJ

pulses per burst 4 pulse distance 0,1 s to 3 s

b)a) c)

Ablated structures in:a) Al2O3b) sapphirec) steel

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Process know-how / laser techniques

Parameter:

l = 10 HzEB = 2 mJl = 14 ns to 50 nst= 0,1 s to 2s

purpose

high ablation rate high ablation quality

(melt reduction,small Ra, ...)

ideal ablation parameters

variation of parameters

burst and pulse energy number of pulses per burst pulse duration

pulse distance repetition rate

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double pulse

EB = 2 x 1 mJt = 2 s

triple pulseEB = 3 x 0,66 mJ

t1 = t2= 2 s

=250ns =5s =15s

single pulseE= 2 m J

1 mm

tdel tdel tdel

Process analysis by high speed photography

Pulse bursts:

Results

Plasma of pulse bursts strips of the surface Magnification factor of the plasma volume:

10 for double pulse, 15 for triple pulse Plasma emission of pulse bursts have larger

emission times

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High-speed Microstructuring of Copper, Aluminum and Steel

verage Power at the Sample Surface, Pt 26 W

Maximum Average Pulse Peak Intensity, IP 92 MW/cm

2

M2- Value (focused beam) 1.6

Repetition Rate, f 4.1 MHzWavelength at Workpiece 532 nmPulse Duration, p 13 ps

OscillatorAmplifier

Frequency

Conversion BeamDump

Focusing Optics

and Scanners

Sample

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Results

Top view Top view Cross-section view

Copper

Steel

Aluminium

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Ablation Experiments at FEL

A: ablation experiments in steel 1.4301 (=304) and C70

A1: single pulse ablation

different pulse delays (=rep. Rate.) variation of: - pulse energy

- pulse overlap- wavelength

A2: ablation with pulse bursts

different delays: pulse delay during one burst burst delay

variation of: - number of pulses per burst (1,2,5, )- burst energy- pulse overlap- wavelength

High-speed-photography of plasma dynamics

metallography, SEM and optical microscopy

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Drilling with s-laser radiation

Lena Trippe

/

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Drilling at LLT / ILT with laser radiation

state of the art: single pulse and

trepan drilling with s-laser-radiation stainless steel, nickel-based

superalloy cylindrical hole geometry resolidified melt layers 15m aspect ratio 20 : 1 time / hole < 20s (trepan drilling)

Nd:YAG Slab Laser

pulse duration: 100-500smax. pulse power: 2kWfocal diameter: 40mM < 2

aim: expansion of process limits during

percussion drilling (high speed drilling) metals and ceramics material thickness 5mm aspect ratio > 100 : 1

time / hole

1sinterdepartmentalcooperation of corecompetence teams:

process know-howlaser techniques system technology modelling and

simulation

process limits

understandingof processes

process diagnostic

processmonitoring

processcontrol

modelling,analysis

simulation,numerical

approximation

1mm

60m

single pulse drilling(X5CrNi18-10)

4mm

=60, 200m

trepan drilling

(CMSX-4)

Ad t ti f i t

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Adaptation of processing parameters

< 500nm ablation depth/pulse < 1-5mm< 3mJ pulse energy < 0.1-50J< 1.5mm material thickness < 10mm

quality

complete

removalof material

geometry

...

productivity

ablation rate

...

vapourisation

helicaldrilling

melting

percussiondrilling

10s100ns

?

pulseduration

P k h / l t h i

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Process know-how / laser techniques

variation of parameters: pulse energy pulse duration temporal pulse shape focal position repetition rate ...

development of hole geometryduring one pulse

single pulse drilling

Nd:YAG-Slablaserpulse energy: 180mJpulse duration: 200smaterial: X5CrNi18-10

purposes: reduction of recast layers and

closures cylindrical geometry of hole

=> parameters for percussiondrilling

cross-section of single pulse drillings


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plasma

(spikes)

melt / closure atthe hole entrance

pulse shape

200m

-200 0 200 400 600 800,0

0,1

0,2

0,3

0,4

0,5

0,6

intensity[a.u.]

t ime [s]

single pulse 500s, 500mJ, dt=20shole diameter

decreasing intensity of

laser radiation

Modeling and simulation

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Modeling and simulation

-30 0 30 60 90 120 150 180 210 2400

100

200

300

400

500

600

700

800

900

holedepth[m]

t ime [s]

experiment

simulation

-30 0 30 60 90 120 150 180 210 240-1

01

2

3

4

5

6

7

8

9

intensity[a.u.]

t ime [s]

time scales of physical processes: beginning of melting

and vapourisation time until meltflow

becomes stationary

geometrical scales: hole depth depth where

resolidification occurs hole diameter

Drilling experiments at FEL

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vapour

plasmaabsorption

laserradiation

Analysis of physical processes

absorption of laser radiation (vapour,plasma) at different wavelengths

plasma formation and absorption of laserradiation at different pulse numbers anddelays

development of hole geometrydepending on pulse numbers

find timescales and geometrical scales incomparison to drilling with s-pulses

melt

material


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B: drilling experiments (metals (X5CrNi18 10, CMSX-4, Al, Cu),

ceramics (Si3N4, AlN))B1: single burst drilling

variation of: - number of pulses (1,2,5,10,20,50,100)- different pulse delays

- pulse energy- wavelength

B2: multi-burst drilling variation of: - number of burst (1,2,5,10,20,50,100)

- number of pulses/burst (1,2,5,10)- different pulse and/or burst delays- pulse energy- wavelength

High-speed-photography of plasma dynamics

metallography, SEM and optical microscopy

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Pulsed Laser Deposition

Leonid Moiseev

25Pulsed Laser Deposition

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Anti reflective coating (ZrO2, Al2O3) onarrays of cylindrical lenses of PMMA

Ferroelectric thin films (BaTiO3, PZT)

BaTiO3

Pt

Si

cladding

electro-opticQ-switch

Er:BaTiO3

laser mediumEr:BaTiO3

substrate

Q-switch waveguide laser by PLDand microstructuring

BaTiO3 thin films on Si/Pt

26Pulsed Laser Deposition

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target

processing gas

substrate

Laser radiation

plasma/vapour

Plasma expansion during PLD

27Spectroscopy on laser-induced plasmas

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p py p

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29Heat conduction in the target and absorption by the plasma

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0 1 2 3 40

20

40

60

80

100

BaTiO3

Heat conduction in target

absorption by plasma

Pa

rtitioningo

fopticalen

ergyP[%]

Fluence L[J/cm

2

]

30Kinetic energy of the particles

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Model: Comparison with plume dynamics by iCCD:

elastic collisions

T

prc

mcE

L

i

ikin

3

2

1

1+=

, [1]

inelastic collisions(macroscopic)

23

2

1

1

+

=

T

prc

mcE

L

i

ikin

elastic inelasticmaterialc1[eV/u] c1[eV/u]

c2/MPg

Al2O3 2,3 0,4 4,1 0,8 6,0 0,5ZrO2 1,2 0,2 1,7 0,3 5,0 0,5BaTiO3 0,9 0,2 1,5 0,3 2,5 0,3

[1] Gottmann et. al.: (E-MRS 1997)Surf. Coat. Technol. 100-101, (1998) p. 415

0 1 2 30

5

10

15

20

Collision kinetic models c2=16 x 10

10K/m

2

inelastic, v0=18 km/s elastic, v

0=15 km/s

ZrO2

O2, m=32

L=3 J/cm2

T=20 C

2 Pa

7 Pa10 Pa

20 Pa

100 Pa

Meanvelocity

[km/s]

Distance from target R [cm]

31Ellipsometry: Refractive index of ZrO2 films

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2

5 10 30 100

1.2

1.4

1.6

1.8

2.0

2.2

2.4

Zone 3Zone 2Zone 1

k n

dS=3,5cm;

L=3,5J/cm

2

dS=2,7cm;

L=3,5J/cm

2

dS=2,7cm; L=5,0J/cm2

0.00

0.02

0.04

0.06

0.08

0.10

Calculated kinetic energy Zr

[eV]

Absorptio

nindexk(=

633nm)R

efrac

tiveindexn(=633nm)

TS=20 C

L=3.5 J/cm2

The bulk values n=2.2 and k=0

are achieved at =20 - 50 eV

32Deposition Experiments at FEL

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C: deposition experiments of oxides and fluorides

C1: ablation for plasma diagnostics

optical emission and absorption spectroscopy

variation of: - different pulse delays

- pulse energy- wavelength

C2: pulsed laser deposition with pulse bursts measurement of deposition rate, optical and structural filmproperties and correlation with plasma parameters

variation of: - number of pulses per burst- burst energy- wavelength

33Aim of all planned Experiments & Conclusion

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Analysis of physical processes ablation

process efficiency: absorption of laser radiation in vapour/ plasmaat different wavelengths and pulse energies,

kinetic energy of particles: plasma expansion and absorption oflaser radiation using different pulse numbers, delays and energy

correlation of the physical processes with the resultingdeposition/ablation rate and film properties

modelling of the processes using the FEL-parameters

Find out parameters for

the deposition of high quality films at high deposition rates (>1 m/s/cm2) the ablation/drilling with tailored pulse trains to precondition the surroundinggetting melt-free structures

34Aachen and ILT

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Rathaus Dom

Carl der Grosse

Marktplatz

ILT&LLT

35Adaptation of processing parameters

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fs-pulses:

lower ablation rate high quality

ms-pulses:

high ablation rate lower quality

tpt-project:

high ablation rate high quality

36Modeling and simulation

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Model for ablation process:

Following pulses againinteract with the surface

VPB >> VSP, mPB >> mSP drSP/dt< 0, drPB/dt> 0 single pulse: spheric

discoid

pulse burst: discoid spheric

consequence of theprecondition due to the previouspulses

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