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High Power Pulsed Fiber Laser
Development for CO2 Space
Based DIAL System
G. Canat, J. Le Gouët, L. Lombard, A. Bresson, J.B. Dherbecourt, D. Goular, A. Dolfi-Bouteyre,
S. Duzellier, D. Boivin,
Onera, The French Aerospace Lab, Chemin de la Hunière 91761Palaiseau, France
Johan Nilsson, Jayata Sahu,
Optoelectronics Research Center, University of Southampton, United Kingdom
Sylvain Bordais
Keopsys, 2 rue Paul Sabatier, 22300 Lannion, France
Outline
• System design overview
• Stabilized oscillators developpment
• Preliminary results for three stages power fiber amplifier
• Test of a radhard version of the preamplifier
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ICSO 2014 – G. Canat
Laser transmitter specifications
HEPILAS project goal: develop a fiber laser for CO2 DIAL at 1579nm.
Various concepts for CO2 lidars transmitters:
1572 nm / fiber / IM-CW
1570 nm / semiconductor MOPA / RM-CW
1572 nm / fiber / pulsed
ESA project HEPILAS approach:
1579 nm / fiber / pulsed
CO2 IPDA + altimetry measurement
2051 nm / bulk / pulsed
2051 nm / fiber / pulsed
Pulse duration 150 ns
Pulse energy
ON 250µJ / OFF 200 µJ (SOW 2 mJ/ 200µJ)
PRF 2 kHz for ON/OFF sequence
Single frequency emission
M2<2.5 with good beam pointing stability
Handle 10 kRad radiation
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System design overview
Stabilized ON1 oscillator
1579.11nm
Master
oscillator
locked on CO2 line
Stabilized ON2 oscillator
1579.12nm
Fiber
switch
Stabilized OFF oscillator
1579.2nm
Stage 1
Core pumped
Stage 2
Cladding pumped
Pp=300W
Ep=45 µJ
Preamplifier
Pp=2kW
Ep=250 µJ
Stage 3
Core pumped
Power amplifier
Pump laser
Optical interface
Control interface
Computer control
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ICSO 2014 – G. Canat
Outline
• System design overview
• Stabilized oscillators development
• Preliminary results for three stages power fiber amplifier
• Test of a radhard version of the preamplifier
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ICSO 2014 – G. Canat
Stabilized oscillator: Preliminary Design
Master laser: wavelength modulation to lock it on the top of the CO2 line
DFB LD
Tdriver
1x2
I driver
1x2 Master Laser
A
output
Iso.
+
Master : low bandwith
DDS
“Long term”
LPF
P. Co
loop neededlow
(WM)
PD
2
Mixer
Master Laser
C
réf.
Lock
Slave lasers: beatnote locking
DFB LD
Tdriver
I driver
C
1x2
2x1
Iso.
Laser
réf.
Laser OFF (or ON)
output
PD
Mixer
VCO
0.5 or 11 GHz
“Long term”
Lock
F to V
LPF
Seed lasers with good short term stability
Long term stability given by locking
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D or B1
Seed lasers: Preliminary Tests on 2 commercial DFB
Beatnote between two independent DFB lasers measured by counter + wavemeter
WAVEMETER
diode 3
diode 1
-1/2
Noise 2.0 MHz.Hz
10
Diode 1 / Diode 3
20
SPECTRUM ANALYSER
beatnote 1-3
-1/2
Noise 0.8 MHz.Hz
HIGH SPEED COUNTER
beatnote 1-3
 Allan [MHz]
beatnote offset (MHz)
19
18
17
16
220
 155 kHz @10s
2
SPECIFICATION
0,2 MHz @10 s
1
15
14
13
0,1
12
0
50
100
150
200
0,1
1
10
time (s)
100
1000
10000
 [s]
Width measurement: Beatnote between two Independent DFB lasers
on 15 ms
Gaussian (f=1000 kHz)
on 16 s
Gaussian (f=2000 kHz)
-10
-15
detected power (dBm)
-20
2MHz @15s
-25
-30
-35
-40
-45
-50
-20M
-10M
0
f [Hz]
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ICSO 2014 – G. Canat
10M
20M
Locking to a CO2 line
Longterm drift
CO2 line
LDC250 + 200 Hz filter
vs
LDC8002
2,10E+009
1,0
~ 40 h
Transmission
~ 50 MHz
BeatNote Frequency (Hz)
0,9
2,05E+009
L=30 m, 8 mbar of CO2
Experiment
HITRAN estimate
450 MHz
0,8
0,7
0,6
1578.222 nm
0,5
-3
2,00E+009
0
50000
100000
0
3
6
relative Frequency  (GHz)
150000
Time (s)
Error signal
Locking
3
Voltage (V)
2
1
Frequency (THZ)
190,08715
Transmitted Signal
Error Signal
Slope of 6,7 mV/MHz
0
Imposed Perturbation
150 MHz @ 2 Hz
190,08710
190,08705
Lock "ON"
190,08700
-1
0
-0,10
-0,05
0,00
0,05
Time (s)
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ICSO 2014 – G. Canat
0,10
10
20
Time (s)
30
Outline
• System design overview
• Stabilized oscillators developpment
• Preliminary results for three stages power fiber amplifier
• Test of a radhard version of the preamplifier
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Brillouin scattering in optical fiber
Stimulated Brillouin Scattering
Pump wave at p
Stokes wave at s=p-B
Acoustic wave at B
gBL
P
eff
out
Threshold condition:
21
A
eff
• Use of LMA with MFD >> 30 µm
Compatibility with good beam quality ?
•
10
Use of highly doped short fibers
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•
Longitudinal variation of Brillouin
frequency using strain…
Compatibility with other requirements (beam
quality, efficiency, lifetime…)?
• Control of dopants concentration profile
Compatibility with complex compositions, high
efficiency, immunity to radiation induced
attenuation ?
Comparison of glass matrix with respect to RIA and gain
Exploration of 3 Erbium doped glass families:
• Aluminosilicate (fiber L)
• Phosphosilicate (e.g. Erbium-Ytterbium) fiber EY
• Aluminophosphosilicate (fiber C)
Gamma ray irradiation
Absorption
1,0
0,9
Erbium
absorption
band
-0,4
0,8
Absorption (U.A.)
RIA dB/m @ 10 kRad
-0,2
-0,6
-0,8
-1,0
1
Fiber C
Fiber EY
Fiber L1
Absorption (U.A.)
0,0
0,7
0,1
Fiber C
Fiber EY
Fiber L1
0,6
0,01
1550
0,5
1560
0,4
0,3
Fiber EY
Fiber L
Fiber C
-1,2
0,2
0,1
-1,4
0,0
1000
1100
1200
1300
1400
1500
1600
Wavelength (nm)
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ICSO 2014 – G. Canat
1700
1570
1580
Wavelength (nm)
1425
1450
1475
1500
1525
Wavelength (nm)
1550
1575
1600
1590
1600
Comparison of aluminophosphosilicate based large mode
area fibers for the power amplifier
1532nm
pump laser
1565nm or 1579nm
DFB

PA
MUX
8°
MFA
FUT
3,5
1,6
3,0
Output power (W)
1,2
2,0
Slope 59%
1,5
Slope 30% Gmax=3.9
1,0
1579nm Pin=160mW
1579nm Pin=316mW
4,5
slope 20%
slope 16%
0,8
0,6
slope 5%
Slope 28%
Gmax=4.4
2
3
4
5
6
Launched pump power (W)
Single mode fiber C
Effective area ~95µm2
ICSO 2014 – G. Canat
3,0
slope 37%
2,5
2,0
slope 28%
1,0
0,0
1
3,5
1,5
0,2
0,0
380mW
100mW
4,0
slope 13%
1,0
0,4
0,5
12
1565nm Pin=126mW
1565nm Pin=281mW
1579nm Pinj=225mW
2,5
Output power (W)
1,4
1579nm Pinj=153mW
Output Power (W)
1565nm Pinj=120mW
0,5
3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,5 7,0 7,5 8,0 8,5 9,0 9,5 10,0
Pump power (W)
LMA fiber B
Effective area ~ 500µm2
3
4
5
6
7
8
9
10
11
Launched pump power (W)
Aluminosilicate LMA fiber L
Effective area ~ 706µm2
Preliminary MOPFA set-up
Pulse shape
Supergaussian fit
1,0
RF Driver
Pulse generator
0,6
0,4
0,2
0,0
0
50
100
150
200
250
300
350
400
450
500
Time (ns)
1579nm
DFB laser diode
Amp 11
AOM
ISO
Amp 21
ISO
Filter
L
Expected SBS threshold increase
MUX
LMA fiber L
Keopsys Raman
fiber laser
Mode
Er 60-40/250 DC
Field
Adaptation
30 W peak power
150 ns pulses
20
18
Backscattered power (U.A)
Power (normalized)
0,8
Unstrained fiber
Strained fiber
16
14
40 MHz
12
10
225 MHz
8
6
4
2
0
10.8
10.9
11.0
11.1
11.2
11.3
Frequency (GHz)
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ICSO 2014 – G. Canat
11.4
11.5
11.6
Experimental results
2000
FWHM=152ns
0,06
1.7 kW
1600
1400
Power (A.U.)
0,05
240
0,03
2000
180
Peak power (W)
0
100
200
300
400
500
600
700
140
1000
120
800
100
550W
SBS limit standard amplifier
80
Pulse energy (µJ)
160
0,00
Time (ns)
600
Chi^2/DoF
= 1589.75337
R^2
= 0.99778
200
0,02
0,01
1200
Data: Data1_B
Model: gauss_beam
2500
220
0,04
Beam diameter (µm)
1800
M2 measurement
260
0,07
w0
z0
zR
40
200
20
0
0
1000
1500
2000
2500
3000
3500
1000
500
2
M <1.2
0
0
50
100
Launched pump power (mW)
M2<1.2
Strain will require large strain during proof testing (250 kpsi) to
provide low probability of failure of the fiber.
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ICSO 2014 – G. Canat
150
Position (mm)
4000
23% optical-optical efficiency
±31.72084
±0.57764
±1.68396
1500
60
400
121.08779
142.1391
6.34922
200
250
Outline
• System design overview
• Stabilized oscillators developpment
• Preliminary results for three stages power fiber amplifier
• Test of a radhard version of the preamplifier
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A rad-hard fiber for the preamplifier
ICSO 2014 – G. Canat
Irradiation configuration of the double pass
amplifier
Radiation
area
FUT specially developed by iXFiber
Mode field diameter 5.6µm
PMF1550
10m
Peak absorption 25.1 dB/m @ 1530nm
Circ
Peak absorption 15 dB/m @ 980nm
1480nm
DBR pump diode
Tap coupler
1%
Fiber well suited for 1579nm amplification
WDM
1580nm
DFB seed laser diode
FUT
11m
20krad
Double pass well suited to reduce RIA impact
Seed
monitor
Output
monitor
Input power 4 µW @ 1579nm
FBG
30 dB of gain
0.8
0.6
0.4
Power density (dBm/nm)
Preirradiation
Postirradiation D+7
Postirradiation D+54
4
Signal output power (mW)
Output power (Normalized)
10
5
1
3
2
5
10
15
20
-10
-20
-30
working point during irradiations
-50
0
0
Preirradiation
Postirradiation
0
-40
1
0.2
0
PMF
1550
10m
25
Doser (kRad)
0
20
40
60
80
100
120
Launched pump power (mW)
-63% drop for 20 kRad dose
Moderate self healing
Power can be recovered by a
modest increase of pump
power (+25%)
ICSO 2014 – G. Canat
-60
1540
1560
1580
Wavelength (nm)
1600
1620
Conclusion
• We report on the preliminary design of an all fiber laser emitting at 1579nm (three
laser lines)
• 3 stages MOPFA based on a core pumped LMA aluminosilicate fiber and a strain
distribution (broadening ~x5 of Stokes spectrum)
• 23% internal optical-optical efficiency
• Good beam stability is preserved
• Development and tests of alternative glass hosts for the various amplification
stages have showed that lab grade aluminophosphosilicate fibers reduce RIA
but lack of gain at 1579nm
• Commercial fiber (iXFiber) well performing in the preamplifier (small core
diameter)
Acknowledgement to European Space Agency who funded part of this work under
under ESA contract #4000104022/11/NL/CP
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CW Oscillator : Prelminary Tests
Free running laser fulfills requirement : 0.2 MHz – 10 sUSB?or GPIB PC Link
3) record Beatnote central
frequency
Laser Mount
(LM14S2 or LDM4980)
+ Laser Diod
(62759-Ax)
TEC c ontroler
(TED8020)
PM Isolator
(PMI-2-56-P-2-L-Q)
PM Coupler 90/10
(PMFC-56-1-10-2-L)
Synthetiser 0.5-1GHz
(BSVB 13)
Frequency to Voltage
Converter
Low Pass filter
(SLP 70+ ) (based on AD650)
Mixer
(ZP 5LH-S+ )
Current sourc e
(LDC 8001 or LDC8002
or LDX3620B-LN))
PM Isolator
(PMI-2-56-P-2-L-Q)
PM Coupler 90/10
(PMFC-56-1-10-2-L)
Photodiod
Attenuator
(EigenLight 420) (SIR-5)
Spectrum Analyzer
(FSP-7)
Coupler 4x25%
(TWC-14-155-0-00-FC/APC-E)
PM Isolator
(PMI-2-56-P-2-L-Q)
19
PM Coupler 90/10
(PMFC-56-1-10-2-L)
ICSO 2014 – G. Canat
BNC-2110
PCI-6251
Computer
Wavelength meter
(WS-6 IR)
1) Direct wavelength
Measurement (Rb referenced)
2) Beatnote spectrum measurement
(~ spectrum autoconvolution)
Spectral and spatial measurements
Long term beam fluctuations assesment
Output spectrum
520
270
0
500
260
480
-10
460
-20
Radius (pixels)
Centroid position (pixels)
Power (A.U.)
250
440
420
400
230
380
-30
240
360
220
340
320
1550
-40
1460
1480
1500
1520
1540
1560
1580
1600
1555
1560
1565
Wavelength (nm)
1570
1575
1580
Centroid position X/Y
210
1550
1555
1560
1565
Wavelength (nm)
1570
1575
1580
Beam radius
Wavelength (nm)
M2 measurement
Data: Data1_B
Model: gauss_beam
2500
Chi^2/DoF
= 1589.75337
R^2
= 0.99778
Beam diameter (µm)
2000
w0
z0
zR
121.08779
142.1391
6.34922

 0.25

±31.72084
±0.57764
±1.68396
1500
1000
500
2
M <1.2
0
0
50
100
150
200
250
Position (mm)
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ICSO 2014 – G. Canat
Single frequency pulse amplification at M2<2:
previous results
2200
2000
1800
Peak power (W)
1600
2
M =1
NP Photonics 2010
2
M ~2.1
ORC 2004
ONERA/IPHT 2008
2
M =1.3
1400
Erbium-Ytterbium standard core
Erbium-Ytterbium multifilament
Erbium-Ytterbium phosphate glass
1200
1000
800
600
Fibertek
2
2014 M =1.2
450µJ
400
RIP control difficult
Aculight 2007
2
M =1
200
0
1530
1540
1550
1560
Wavelength (nm)
Low efficiency
Parasitic effects
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ICSO 2014 – G. Canat
1570
NP Photonics
2
2010 M =1
80µJ
1580