high power fiber lasers emitting at 1030 nm and 976...

High power fiber lasers emitting at High power fiber lasers emitting at 1030 nm and 976 nm1030 nm and 976 nm

E. CormierE. Cormier

CELIA UniversitCELIA Universitéé Bordeaux IBordeaux I--CNRSCNRS--CEA, CEA,

351 cours de la Lib351 cours de la Libéération Fration F--33405 Talence, France33405 Talence, France

E. Cormier CMDO 2010E. Cormier CMDO 2010

1. Introduction

2. Fiber lasers at 1030 nmn

Sub 300 fs: Fiber CPA

Sub 100 fs: Direct amplification

Sub 10 fs: Few cycles with OPCPA

3. Fiber lasers at 976 nm

Main issues

High power : CW laser

High energy: Q-switch

High peak power: Mode-lock systems

Blue Light

High brightness pumping of Yb-doped materials

OutlineOutline

22


1. Introduction






Main issues




Blue Light


OutlineOutline

33


• Large amplification bandwidth• Limited thermo-optical problems• Excellent beam quality• Efficient diode pumping operation• High single pass gain• Large variety of doping ions• Compactness

A revolution in laser technology: fiber lasers A revolution in laser technology: fiber lasers

44


Bulk rod

Diode pumped solidDiode pumped solid--state laser evolutionstate laser evolution

HR-Mirror Output coupler

Laser beam

Gain mediumlens

End pumped bulk laser

Output coupler

Gain medium

Laser beam

HR-Mirror

lens

Laser Diode

Side pumped bulk laser

Laser Diode

55


rod


Stress-induced birefringence

Hot

Cold

Thermal lensing

Low power High power

Beam distortions

Laser1060 nm

E0

E2

E3

E1

Heat

Heat

Pump808 nm

Nd3+

Quantum defect = 24 %

66


diskslab fiber

reduced thermo-optical distortions


HR-Mirror Output coupler

DiskCooling

Laser DiodeLens

Disk laser

Laser beam

Laser Diode

lens

Fiber

HR-Mirror

Laser DiodeLens

Slab

HR-Mirror

y

z

Slab laser

Fiber laser

77



Heat is spread over long distances in fibers

88


nCore

nCladding

n

Refractive Index profile

Laser radiationPump

Active inner core

• Core size < 10 µm• Requires single mode pumping diodes• Pumping limited to 1 W• Length: 10..100 m (non linear effects)

Not compatible with high power

Standard single mode active fiberStandard single mode active fiber

99


nCoating

ncore

ncladding

Laser beam

PumpInner claddingActive core

[1] E. Snitzer et. al., Optical Fiber Communication Conference, PD5, 1988

Outer claddingRefractive Index

profile

n

ØcoØcl

• High power multimode pumping diodes

• but higher core doping: ~ Øco/ Øcl

Double clad fiberDouble clad fiber

1010


Step index Step index vsvs airair--clad clad microstructuredmicrostructured fibersfibers

1111


Typical Typical microstructuredmicrostructured fibers used in our systemsfibers used in our systems– Large core diameter with

diffraction limited operation

–– Polarization maintaining design for Polarization maintaining design for environmentally stableenvironmentally stable operationoperation

-- AirAir--clad clad microstructures for microstructures for pump propagation pump propagation (NA (NA = 0.6)= 0.6)

Rod type fiber

Flexible fibers

80 80 μμmm (NA < 0.02) (NA < 0.02)

40 40 μμmm (NA < 0.01) (NA < 0.01)

1212


1. Introduction






Main issues




Blue Light


OutlineOutline

1313

E. Cormier CMDO 2010E. Cormier CMDO 20101414D. Strickland and G. Mourou, “Compression of amplified optical pulses,”Opt. Comm. 56, 3, 219 (1985).

Chirp Pulse Amplification

CPA fiber amplifier: sub 300 fsCPA fiber amplifier: sub 300 fs

I =E

A .τReduced peak powerReduced nonlinear effects


GratingCompressor

Power Amplifier

Pulse picker

Grating stretcher

Isolator

Pre-amplifier

Fiberstretcher

E = 100 µJT = 270 fsf = 300 kHzP = 340 MWΔλ = 7.2 nmPav = 30 W

M2 = 1.3

Y. Zaouter et al, Optics letters 33, 1527 (2008)J. Boullet et al, Optics letters 34, 1489 (2009)



1000 800 600 400 200 0

10

100

1000 1 GW

200 MW

50 MW

500 MW

Effe

ctiv

e Pu

lse

Ener

gy (µ

J)

Pulse duration (fs)

JenaImraCeliaSouthamptonCornellIotaCUOS

100 kHz

Y. Zaouter et al, Optics letters 33, 1527 (2008)J. Boullet et al, Optics letters 34, 1489 (2009)1616



Direct amplification: sub 100 fs

DiodesDiodes60 W @ 976 60 W @ 976

nmnm

Yb:KYWYb:KYWoscillatoroscillator

OI

Transmission Transmission gratinggrating

1740 l/mm1740 l/mm

MicrostructuredMicrostructuredrodrod--type 80/200 type 80/200

fiberfiber

OutputOutput

1717


Spectrum extends up to 60 nmModulations smoothed out due to amplification

•• Gain: Gain: I(zI(z) = I) = I00 exp(exp(αα.z.z) ) •• SPM: SPM: ωω(t(t) = ) = ωω00 (1(1--LnLn²²/c /c dI/dtdI/dt))•• asymmetric gain asymmetric gain

980 1000 1020 1040 1060 10800.0

0.2

0.4

0.6

0.8

1.0

Inte

nsity

[a.

u]

Wavelength [nm]

980 1000 1020 1040 1060 10800

20

40

60

80

Wavelength [nm]Pr

opag

atio

n di

stan

ce [c

m]

1818



-600 -400 -200 0 200 400 6000.0

0.2

0.4

0.6

0.8

1.0

Inte

nsity

[a.

u]

Time [fs]

47 fs8.6 W (0.86 µJ)

-400 -200 0 200 400500

510

520

530

Delay [fs]

SHG

Wav

elen

gth

[nm

]

-600 -400 -200 0 200 400 6000,0

0,2

0,4

0,6

0,8

1,0

Inte

nsity

[a.

u]

Time [fs]

66 fs12.5 W (1.25 µJ)

-400 -200 0 200 400500

510

520

530

Delay [fs]

SHG

Wav

elen

gth

[nm

]

18 MW: 1.25 µJ @ 65 fs

10 MHz

Y. Zaouter et al, Optics letters 33, 107 (2008)Y. Zaouter et al, Optics express 15, 15, 9372 (2007)1919



Signal stretcher

Yb Fiber CPA pump

Parametricamplifiers Compressor

Signal source

Pumpsource

FCPA pumped OPCPA : sub 10 fs

2020


CEP stabilized

Modelocked source

Signal stretcher

Yb Fiber CPA pump

Parametricamplifiers Compressor

60%60%

Rainbow

• 7 fs Ti:Sapph Oscillator• 300 nm @ -10dB• CEP stabilized

Signal Pump

20 pJ @ 1030

2121



Rainbow Spectral Selection Unit

To NOPA

To FCPA

SHG unit

2222



CEP stabilized

Modelocked source

Signal stretcher

Yb Fiber CPA pump

Parametricamplifier Compressor

FCPA Pump

Rainbow signal

To SHG-FROG

BBO Type ISF10 prisms

2323



• Spectrum • Duration

1 μJ68 nm amplified bandwidth @ 720 nm10 fs (3.6 cycles)

-40 -30 -20 -10 0 10 20 30 400.0

0.2

0.4

0.6

0.8

1.0

Δτfield = 10 fs

Aut

ocor

rela

tion

time (fs)

Δτautoco = 14,1 fs

14.1 fs

Δτ field = 10 fs

100 kHz

J. Nillon, et al, CLEO 2009 [CWL3] Baltimore USAJ. Nillon, et al, ASSP 2009, [Post Deadline], Denver USA2424


Δλ = 68 nm


1. Introduction






Main issues




Blue Light


OutlineOutline

2525


2F5/2

2F7/2

λp= 976 nm λs=1030 nm

Yb-doped fiber

Configuration 1

Yb-doped fiber lasers operating at 976 nm

2626


2F5/2

2F7/2

λp= 976 nm λs=1030 nm

Configuration 1

2F5/2

2F7/2

915 nm 1030 nm

Configuration 2

976 nm

Yb-doped fiber Yb-doped fiber

2727



σsabs

σsem

σsem ~σs

abs

Issue # 1 :Transparency:

Bleaching is achieved if :

for a pump intensity of:

%502 ≈+

= ems

abss

abss

Tot

trans

nn

σσσ

2kW/cm30≈

⎟⎟⎠

⎞⎜⎜⎝

⎛−

=

fluoempabs

s

ems

absp

ptransp

hI

τσσ

σσν

σsabs

σsem

Transparency at 1030 nm achieved for inversion ~5% …

2828



Issue #2: Gain competition between quasi and true 3-level laser operation :

βα pGG 72.025.0 9761030 +=

Pump absorption Clad to core area ratio

Rod type U-LMA PCF : 80 / 200 µm

β=6.2 : αp=9 dB => G1030 nm< 50 dB

Φclad=200 µm => Pp ~ several 100W

2929



High power CW laser at 976 nm

Rod type fiber :Rod type fiber :MicrostructuredMicrostructuredDouble clad Yb dopedDouble clad Yb doped8080µµm/200m/200µµmmAbsorption: Absorption: 10 dB/m10 dB/mLength : 1.2 m Length : 1.2 m

1 Pptrans = 11 W

2 β = 6.2, losses = 60 dB Boullet et al., OE 16, 17891 (2008)

3030


0 25 50 75 100 125 150 175 200 225 2500

102030405060708090

100110120

Las

er P

ower

@ 9

76nm

(W)

Pump Power @ 915nm (W)

Slope Efficiency = 48%

Ptreshold= 18W

970 972 974 976 978 980 982 984 9860.0

0.2

0.4

0.6

0.8

1.0

Inte

nsity

Wavelength (nm)

950 960 970 980 990 1000 1010 1020 10301E-5

1E-4

1E-3

0.01

0.1

1

Inte

nsity

(Log

scal

e)

Wavelength (nm)

ASE

35 dB

94 W

M2 = 1.35

977.5 nmEfficiency : Spectrum :

Parasitic lasing suppression :Beam quality :

3131

High power CW laser at 976 nm

Boullet et al., OE 16, 17891 (2008)


High energy Q-switch laser at 976 nm

MOPA: Master Oscillator Power Amplifier

Oscillator

Amplifier

Acousto-optic modulator

Boullet et al., OL 35, 1650 (2010)


High energy Q-switch laser at 976 nmO

utpu

t pow

er [W

]O

utpu

t pow

er [W

]

Pump power [W]Pump power [W]

Slope efficiency Slope efficiency ≈≈ 35 %35 %Amplification threshold = Amplification threshold = 27 W27 W

T= 35T= 35µµss

INTERPULSE ASEINTERPULSE ASE78 W @ 190 KHz, 32 ns

1 mJ @ 10 KHz, 12 ns

Or

M2 < 1.4

Boullet et al., OL 35, 1650 (2010)

78 W


High peak power mode-lock laser at 976 nm

970 972 974 976 978 980 982 9840.00

0.25

0.50

0.75

1.00

Inte

nsity

[a.u

.]

Wavelength [nm]980 1000 1020 1040

-40

-30

-20

-10

0

Inte

nsity

[dB

]

Wavelength [nm]

Δλ1/2 = 5 nm

Δλ1/e2 = 10 nm

30 dB

Mode- Locking: non-linear polarization evolutionAll-normal dispersion

Lhermite et al., OL 35, 3459 (2010)


Output pulsesOutput pulses Compressed pulsesCompressed pulses

-2 0 2 4 6 8 10 120.0

0.2

0.4

0.6

0.8

1.0

Sign

al

Delay [ps]

Δτ = 1.44 ps = 1.41 x 1.02 ps

0.0 0.5 1.0 1.5 2.0 2.5 3.00.0

0.2

0.4

0.6

0.8

1.0

Sign

al

Delay [ps]

Δτ = 402 fs = 1.41 x 285 fs

Pav = 480 mW

ν = 40.6 MHz

E = 11.8 nJ

Δλ = 5 nm

Δτ = 285 fs

Ecompressed = 6 nJ !!!

Ppeak = 21 kW

50 % compressor efficiency only !! Potentially 37 kW

High peak power mode-lock laser at 976 nm

Lhermite et al., OL 35, 3459 (2010)


Blue light generation at 488 nm

LBO crystal ωλ/2 λ/4 DM

2ω

High energy fiber laser

59 W @ 977 nm

High energy fiber laser

59 W @ 977 nm

36 % 36 % efficiencyefficiency

16.1 W 16.1 W atat 488 nm488 nm

Boullet et al., Europhoton (2010)


Blue light generation at 488 nm

Boullet et al., Europhoton (2010)

Applications of high brightness intense sources at 488 nm Replacement of Ar ion lasersLaser surgeryDermatologyBiophotonicsLaser light shows and laser display RGB


High brightness pumping of Yb-doped materialSingle-mode laser

Multi-mode diode

Single-mode laserMulti-mode diode

Brightness : B =P

S.Ω


High brightness pumping of Yb-doped material

High brightness optical pumping of Yb materials 900 920 940 960 980 1000 1020 1040 1060 1080

0.0

0.5

1.0

Inte

nsity

[a.u

.]Wavelength [nm]

Yb:Caf2

High power High power fiberfiber laserlaser

High power High power diodediode

Source power [W]

Brig

htne

ss[W

/cm

2 /sr]



40 W 40 W

ASE source at 976 nm

TEM00

Up to 40 W

974 976 978 980 9820.0

0.5

1.0

Inte

nsity

[a.u

.]Wavelength [nm]

3 W 15 W 27 W 39 W



Small signal gain up to 10 expected with long cristals


People:F. Labaye (Phd)J. Nillon (Phd) G. Machinet (Phd)J. Lhermite (PostDoc)L. Lavoute (PostDoc)C. Medina (Assistant Engineer, CNRS)S. Petit (Research Engineer, CNRS)S. Montant (Research Engineer, CEA)D. Descamps (Research Engineer, CEA)E. Cormier (Professor, University)

Collaborations:HHG group @ CELIAInstitut d’optique (Palaiseau)Institut of physics, Vilnius University, Vilnius, Lithuania (A. Piskargkas)Institut of Applied Physics (IAP), Universität Jena, Germany (J. Limpert)Photonics Institute, Vienna University of Technology, Vienna, Austria (A. Baltuska)ETH, Zurich, Switzerland (U. Keller)KEK, Tsukuba, Japan (T. Omori, J. Urakawa)Clarendon Laboratory, University Oxford, England (A. Wyatt, I. Walmsley)Eolite systems (Bordeaux)Amplitude systèmes (Bordeaux)CEA CESTA4343

C. Aguergaray (Phd)Y. Zaouter (Phd)J. Boullet (Postdoc)

high power fiber lasers emitting at 1030 nm and 976...

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