presentation pcf high repetition rate

8/13/2019 Presentation PCF High Repetition Rate

1/59

Fraunhofer IOF

5th international workshop on fiber lasers in Dresden 2009

High repetition rate short pulse fiber lasers and

amplifiers: Fundamentals and perspectives

Andreas Tnnermann

Fraunhofer-Institut fr Angewandte Optik

und Feinmechanik IOFAlbert-Einstein-Strae 7

07745 Jena


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Fraunhofer IOF

Laser Focus World 2009, Author: Gail Overton, Stephen G. Anderson

percentage of overall laser revenues

Laser by application


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solid state laser market (2008):1,500 Mio. US$

Laser Focus World 2009, Author: Gail Overton, Stephen G. Anderson

Laser by technology


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Fiber laser market

others; 27%

medicine;7%

material

processing ;67%

others;23%

medicine;

7%material

processing;70%

2005105 Mio. US$

2008300 Mio. US$

fiber laser market:annual growth + 40%

source: Optech Consulting


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Fiber lasers basic principlesHigh power, high energy nanosecond fiber amplifiers

High power femtosecond fiber amplifiers

Laser micromachining

Conclusion

Outline


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power combiner

active fiber

power supplypump diodes

OC (LR FBG)HR FBG

Fiber laser: basic principle


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Fraunhofer IOF

inelastic scattering process of photons on optical phonons

1050 1075 1100 1125 1150 1175 1200

1. StokesLaser

Laserlesitung 100 W 110 W 120 W

i n t e n s i

t y [ a

. E . ]

wavelength [nm]

pP E h=

sS E h=f i EE

Raman-spectrum

Reff

eff SRS g L

AP 16

gB

= Raman-gain coefficient,Aeff = eff. areaLeff = effective interaction lengthG.P. Agrawal Nonlinear fiber optics,Academic Press, 1995

THz pS 13 in silica

0 6 12 18 24 30 36 420,0

0,2

0,4

0,6

0,8

1,0

R a m a n - g a i n

[ * 1 0 - 1

3 m

/ W ]

frequency shift [THz]

Raman-gain coefficient

R. H. Stolen, Proc. IEEE, 68, 1232, 1980

Power scaling limitation nonlinearity (SRS)


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Fraunhofer IOF

microstructured fiber

air

glass d

step-index fiber

2a

n coren cladding

n ~ 110 -4

NA ~ 0.02 n ~ 110 -3

NA ~ 0.06

significantly larger single-mode core possible

N.A. Mortensen, J.R. Folkenberg, M.D. Nielsen, and K.P. Hansen, "Modal cut-off and the V-parameter in photonic crystal

fibers", Opt. Lett. 28, 1879 (2003).

Microstructured fibers


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Fraunhofer IOF

taken from: Kim P. Hansen et.al.

Photonic Crystal Fibers, Photonics West 2005

Air cladding region high NA inner cladding


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Fraunhofer IOF

inner cladding: = 170 .. 210 m (NA > 0.6) ACcore: = 40 .. 50 m, NA = 0.03, MFD ~ 45 m

pump light absorption: >10 dB/m @ 976 nm

strictly single-mode operation with a MFA ~1000 .. 1600 m 2 !!!

outer claddingair-clad

inner cladding

active core

M2 < 1.2

J. Limpert, Low-nonlinearity single-transverse-mode ytterbium-doped photonic crystal fiber amplifier, Opt. Express 12,

1313-1319 (2004).

Extended large-mode-area single-mode RE-doped PCF


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ORC-Southampton,

Great BritanTokyo University,Japan

FSU-IAP, FhG-IOF &IPHT, Jena, Germany

University of Michigan,USA

IPGSPIJDSU / SDLJenoptikNufernCrystal Fibre

1992 1994 1996 1998 2000 2002 2004 20060

200400

600

800

1000

1200

1400

1600

1800

2000step index fiber photonic crystal fiber

370 W

1530 W

2000 W

1360 W

260 W

80 W4 W

1300 W

800 W

600 W

135 W200 W

400 W

150 W170 W

485 W

110 W9,2 W5 W 30 W

270 W

C W

o u

t p u t p o w e r

[ W ]

Year

1900 W

evolution of cw fiber laser

Diode-pumped double clad fiber laser (cw output)


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2002 2003 2004 2005 2006 2007 2008 2009100

1000

10000

IAP

IAP+IOF IPG IPHT+IAP SPI JO+IAP Michigan

O u t p u t

P o w e r

/ W

Year

Diode-pumped double clad fiber laser (cw output)evolution of cw fiber laser


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Fraunhofer IOF

laser core(generated heat)pump corecoating

one-dimensional heat conduction equation

0r K r Q

dr r dT

r 1

dr Td 2

2

=+

+

)(

)()(

Q: generated heat per unit volumeK: thermal conductivity

0 1 2 3 4 50 100 150 200 250 300 350

region of thepump core

region of thelaser core

T [ a

. u . ]

radius [m]

heat conduction

radiative heat dissipationand convective heat flow

TdAdQ k convection =

( )4241radiation TTdAdQ = k: heat transition coefficient

: Stefan-Boltzmann-constant

: emission factor

Temperature profile

Thermo-optical effects


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Fraunhofer IOF

0 2 4 6 8 10 12 14 16 18 20 22 240

2

4

6

8

10

12

1200 W/m extracted

damage threshold

SRS threshold

P o w e r

[ k W ]

Fiber length [m]

@ 40 m core diameter

cw 10 kW-class single-mode fiber laser

Power scaling limitations


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Fraunhofer IOF

ILT, IOF, IWS, IFSW

r F

F

r = r F F

BPP = r

r

beam power [W]

b e a m p a r a m e t e r p r o

d u c t

B P P [ m m m r a

d ]

0,1

1

10

100

10 100 1000 10000

diode laser

fibre laserdisc laser

Nd:YAG-laser

CO 2 -laser

High power lasers: beam quality and output power


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Fraunhofer IOF

Outline

Fiber lasers basic principles

High power, high energy nanosecond fiber amplifiers



Conclusion


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Fraunhofer IOF

seed source

isolator

pre-amp booster

ASE filter isolator

end-cap

Pulsed fiber laser MOPA


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Input Output

OutputInput

Pulsed fiber laser MOPA


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Digital functiongenerator (50kHz)

Analog pulsegenerator + delay

Ch1

Ch2Ch3Ch4

ECDL

30cm, PM-6m

WDM

SM-pump(976nm)

2m, PM-10/125

electronics

pump(976nm)

grating(ASE-filter)

pinhole

pump(976nm)

to combiningstage

1.2m, rod-type PCF, 80/2002

4

Pulsed fiber laser MOPA - 3-stage amplifier


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Fraunhofer IOF



Ch1

Ch2Ch3Ch4

ECDL

30cm, PM-6m

WDM

SM-pump(976nm)

2m, PM-10/125

electronics

pump(976nm)

grating(ASE-filter)

pinhole

pump(976nm)

to combiningstage


4

5W

Pulsed fiber laser MOPA diode laser seed source


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Fraunhofer IOF



Ch1

Ch2Ch3Ch4

ECDL

30cm, PM-6m

WDM

SM-pump(976nm)

2m, PM-10/125

electronics

pump(976nm)

grating(ASE-filter)

pinhole

pump(976nm)

to combiningstage


4

Pulsed fiber laser MOPA - electronics


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Fraunhofer IOF



Ch1

Ch2Ch3Ch4

ECDL

30cm, PM-6m

WDM

SM-pump(976nm)

2m, PM-10/125

electronics

pump(976nm)

grating(ASE-filter)

pinholepump

(976nm)

to combiningstage


4

Pulsed fiber laser MOPA - electronics


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Fraunhofer IOF



Ch1

Ch2Ch3Ch4

ECDL

30cm, PM-6m

WDM

SM-pump(976nm)

2m, PM-10/125

electronics

pump(976nm)

grating(ASE-filter)

pinhole

pump(976nm)

to combiningstage


4

~1mW

5W

Pulsed fiber laser MOPA 1st preamplifier


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Fraunhofer IOF



Ch1

Ch2Ch3Ch4

ECDL

30cm, PM-6m

WDM

SM-pump(976nm)

2m, PM-10/125

electronics

pump(976nm)

grating(ASE-filter)

pinhole

pump(976nm)

to combiningstage


4 0.1W

Pulsed fiber laser MOPA 2nd preamplifier


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Fraunhofer IOF



Ch1

Ch2Ch3Ch4

ECDL

30cm, PM-6m

WDM

SM-pump(976nm)

2m, PM-10/125

electronics

pump(976nm)

grating(ASE-filter)

pinholepump

(976nm)

to combiningstage


4

1031 1032 1033 1034 1035-90

-80

-70

-60

-50

-40

-30

-20-10

S p e c

t r a l

p o w e r

[ d B ]

Wavelength [nm]

Pulsed fiber laser MOPA ASE-filter


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Fraunhofer IOF



Ch1

Ch2Ch3Ch4

ECDL

30cm, PM-6m

WDM

SM-pump(976nm)

2m, PM-10/125

electronics

pump(976nm)

grating(ASE-filter)

pinhole

pump(976nm)

to combiningstage


4 ~50 W1 mJ

Pump core

(200 m)

Active core(80 m)

Air clad

MFD ~ 70 mMFA ~ 4000 m 2

Low nonlinearites!

Pulsed fiber laser MOPA power amplifier


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Fraunhofer IOF

system parameters: o) number of channels = 4o) pulse repetition rate = 50 kHzo) pulse duration = 2.2 ns

Reflection grating

Output

3-stage amplifier

Combining stage

12

34

Sources

:

:

:

Pulsed fiber laser MOPA spectral combining


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P l d fib l MOPA l bi i


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Fraunhofer IOF

Dielectric reflectiongrating

(1030 nm)

(1032nm)

(1034 nm)(1036 nm)

Combinedoutput

(1740 lines/mm)

Folding mirrors

combining efficiency 97%

Pavg

= 187 WEpulse = 3.7 mJP peak = 1.7 MW

Pulsed fiber laser MOPA spectral combining

P l d fib l MOPA hi h titi t


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Fraunhofer IOF

Digital functiongenerator:

f Rep = 5 MHz

Analog pulsegenerator:

5 ns pulses + delay

Ch1

Ch2Ch3Ch4

ECDL

30 cm PM-6m

WDM

SM-LD2 m PM-10/125

electronics

LD

1.6 m PZ-40/200

LD

LD15 m 42/500

Single output

HWP

IF

water-cooled

Pulsed fiber laser MOPA high repetition rate

P l d fib l MOPA high titi t


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Fraunhofer IOF

f rep = 5 MHz, T pulse = 5 ns, 4 laser systems

1032 1034 1036 1038 1040 1042 1044 1046-80

-70

-60

-50

-40

-30

-20

-10

0

4nm

Channel 4Channel 3Channel 2Channel 1

S p e c

t r a l p o w e r

[ d B ]

Wavelength [nm]

Main amplifier fiber

Length ~ 15 mpump core ~ 500 m

active core ~ 42 m




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Fraunhofer IOF

Slope efficiency = 49%

1.1 kWCombining efficiency = 99%

Epulse = 220 J

0 500 1000 1500 2000 25000

200

400

600

800

1000

1200

A v e r a g e o u

t p u

t p o w e r [

W ]

Launched pump power [W]

1.0

1.5

2.0

2.5

3.0

M 2 x

( h o r i z o n

t a l )

combined beam


Nanosecond pulsed fiber laser MOPA


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Fraunhofer IOF

f rep = 50 kHz, T pulse = 2.2 nsP avg = 187 W

Epulse = 3.7 mJP peak = 1.7 MW

f rep = 5 MHz, T pulse = 5 nsP avg = 1100 W

Epulse = 220 JP peak = 44 kW

high pulse energy high average power

O. Schmidt, C. Wirth, I. Tsybin, T. Schreiber, R. Eberhardt,J. Limpert, and A. Tnnermann, "Average power of 1.1 kW

from spectrally combined, fiber-amplified, nanosecond-pulsedsources," Opt. Lett. 34, 1567-1569 (2009).

O. Schmidt, T. V. Andersen, J. Limpert, and A.Tnnermann, "187 W, 3.7 mJ from spectrally combinedpulsed 2 ns fiber amplifiers," Opt. Lett. 34, 226-228(2009).

Nanosecond pulsed fiber laser MOPA

Outline


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Outline





Conclusion

Chirped-pulse-amplification


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Fraunhofer IOF

amplifier

stretched pulseamplified pulse

stretcher compressor

short

pulse

amplifiedshort pulse

D. Strickland and G. Mourou, Compression of amplified optical pulses, Opt. Comm. 56, 3, 219 (1985).

Chirped-pulse-amplification

CPA-fiber amplifier


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Fraunhofer IOF

isolator

Isolator

diode laser

dielectric gratingcompressor

fs-oscillator

preamplifier

diode laser

Yb-dopedpower amplifier

2 W, 10 MHz350 fs, 1030 nm

temporal scalinglarger stretching

factor

spacial scalingincreased mode-field-area

dielectric gratingstretcher

AOM

80 MHz...10 kHz

output

CPA-fiber amplifier

CPA-fiber amplifier high average power system


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820 W average power @ 650 fs

15 MW peak power (78 MHz rep.-rate)

CPA fiber amplifier high average power system

CPA-fiber amplifier high energy system


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autocorrelation trace

0 50 100 150 200 2500

20

40

60

80

100

C o m p r e s s e d o u

t p u t p o w e r

[ W ]

Launched pump power [W]

slope efficiency = 46%

100 W compressed @ 100 kHz1 mJ pulse energy

compressed output

CPA fiber amplifier high energy system

-10 -5 0 5 100.0

0.2

0.4

0.6

0.8

1.0

AC = 1.23 ps

AC = 1.2 ps

AC = 0.93 ps

S H I n t e n s i t y

[ a . u . ]

Time delay [ps]

200/80 Rod-type PCF

Fiber lasers and amplifiers: peak power


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Fraunhofer IOF

1992 1994 1996 1998 2000 2002 2004 2006 20081k

10k

100k

1M

10M

100M

1G

10G

Uni Jena IMRAUni Bordeaux

Cornell Uni P u

l s e p e a k p o w e r

[ W ]

year

evolution of peak pulse of high repetition rate ultrafast fiber laser

Fiber lasers and amplifiers: peak power

Outline


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Conclusion

Interaction of intense laser radiation with solids


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Fraunhofer IOF

long pulses ( > 10 ps) ultrashort pulses ( < 1 ps)

Skin-depth ~ 10 nmv

expansion~ v

sound~ 10 5 - 10 7 cm/s

xplasma (100 fs) ~ 1 - 10 nmxplasma (10 ns) ~ 100 - 1000 m

Plasma Shielding!

Plasma expansion


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Streak camera image of an expanding laser produced tungsten plasma

laser pulseplasma

frontv

expans= 510 6 cm/s

expanding plasma

p

Time scales in ultra short pulse machining


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Fraunhofer IOF

fs ps ns s

energydeposition

electronicthermalization

electron latticeenergy exchange

ablation

max. rep.-rate: 100 kHz 1 MHz

p g

Precision drillings in steel


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Fraunhofer IOF

entrance

exit

material: steelthickness: 200 mpulse duration: 170 fsfluence: 2.5 J/cm

high aspect ratio!


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Polarization trepanning


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Fraunhofer IOF

linearly polarized

material: steelthickness: s = 1.0 mm

diffractive opticsenvironment: air

rear surface

Micro-drilling of stainless steel


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Fraunhofer IOF

entrance

hole diameter: 50 mmaterial: 1.4301thickness: 0.2 mm

combination of DOE andlens:

DOE : ring-profilelens: f = 40 mm

pulse duration: 120 fs

pulse energy: 600 Jrep. rate: 1 kHz

process gas: Helium

exit

array

detail detail

arraydrillings parameters


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Precision drillings in steel


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Fraunhofer IOF

fuel injection nozzlesdetails of fs-drilled hole

exit replica

entry

material: steelpulse duration: 120 fsfocal length: 80 mm

Analytical solution of the cooling cycle after a single pulse for t

Heat accumulation


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Fraunhofer IOF

( )21

20

4 / Dt t

w I T l a

=

Ia : absorbed laser-light intensityW 0 : beam waist l : pulse duration : thermal conductivityD : heat diffusivity : repetition rateE

p :Pulse energy

N.P. MELT = T M / T

Minimum number of pulses to reach the melting temperature:

Analytical solution of the cooling cycle after a single pulse for t l

t = 1/

25234 /

/

=

Pl

M MELT

E A

T D NP

D. Buerle, Laser Processing and Chemistry (1996)


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Percussion drilling of stainless steel


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Fraunhofer IOF

: 1030 nmpulse width: 800 fs

pulse energy: 70 J

focal length: 25 mmfluence: 33 J/cm 2

0 100 200 300 400 500 600 700 800 900

0.01

0.1

1

Repetition Rate (kHz)

B r e a

k t h r o u g

h T i m e ( s

)

Fe/Cr18Ni10

thickness0.5 mm1 mm

Laser trepanning @ 510 kHz


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Fraunhofer IOF

laser fluence: ~ 1 J/cm 2

trepanning radius: 75 mrotating speed: > 100 rounds/sbreakthrough time: 800 ms

stainless steel (Fe/Cr18Ni10),thickness: 0.5 mm

Outline


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Conclusion

Conclusion


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Fraunhofer IOF

short pulse fiber lasers and amplifiers

Pulse-energy: mJ-range

Peak power: GW-range

Average power: kW-range

novel applications in science and industry


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Fraunhofer IOF

FhG IOFFhG IOF

FSUFSU -- JenaJena IAPIAP

presentation pcf high repetition rate

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