requirements
AdvLIGO – optical layout
AdvLIGO PSL – subsystem layout
power stabilizaiton
front end
20W
power
stages
200W
premode
cleaner
170W
reference
cavity
frequency stabilization
mode
cleaner
long
baseline
cavities
Advanced LIGO PSL – requirements
Power / Beamprofile:
– 165W in gausian TEM00 mode
– less than 5W in non- TEM00 modes
Drift:
– 1% power drift over 24hr.
– 2% pointing drift
Control:
– tidal frequency acuator +/- 50 MHz, time
constant < 30min
– power actuator 10kHz BW, +/-1% range
– frequency actuatot BW:<20o lag at
100kHz, range:
DC-1Hz: 1MHz,
1Hz-100kHz: 10kHz
frequency noise requirement
intensity noise requirement
further PSL requirements
• interfaces to detector control software
• interfaces to DAQ system
• environmental requirements: size, power,
cooling
• reliability to meet detector duty cycle goal
• easy to maintain (change of items with
lifetimes < 2years)
concept
PSL optical layout
high power
ring laser
200W
GEO typ
ring laser
15W
spatial filter
resonator
(PMC)
NPRO
1W
frequency
reference
resonator
AOM
Advanced LIGO Laser Design
output
f QR
NPRO
f
FI
BP
EOM
FI
modemaching
optics
f QR
HR@1064
HT@808
f
YAG / Nd:YAG
3x2x6
f
2f
f
YAG / Nd:YAG / YAG
3x 7x40x7
High Power Slave
20 W Master
PSL – stabilization scheme
intensity stabilization
outer loop
injection locking
intensity stabilization
inner loop
PMC loop
frequency stabilization
inner loop
frequency stabilization
outer loop
pre-stabilized -LIGO 10W laser
length controll
intensity controller
NPRO
EO
pre-mode
cleaner
power
amplifier
to suspended
mode cleaner
temp PZT
EO
phase
shifter
frequency
contoller
AO
mixer
reference
cavity
LIGOI reference cavity, AOM, tidal
correction
pre-modecleaner
fu se d s ilic a sp a c e r
M 1
M 3
M 2
PZT
• 713 MHz free spectral range
• linewidth: 162 kHz in s-pol. , 3.2 MHz in p-pol.
• circulating power 0.135MW/cm2 (for p-pol.), 2.64MW/cm2 (for s-pol.)
• linewidth required to filter RIN(@25MHz) of 180W laser: 3.7MHz
status
PSL set-up
high power
ring laser
200W
GEO typ
ring laser
15W
spatial filter
resonator
(PMC)
NPRO
1W
frequency
reference
resonator
AOM
Nd:YAG Master-Laser
NPRO (non-planar ring
oscillator) by Innolight*
• output power: 800mW
• frequency noise:
[ 10kHz/f ] Hz/sqrt(Hz)
• power noise:
10-6 /sqrt(Hz)
* US dristibution: Resonant optics Corp., San Martin CA
High Power Locking Scheme
Master
• 2W Miser
Mephisto 2000 Innolight
• EOM: New Focus
@ 29,02 MHz
20% OC
HR
20% OC
HR
Brewster Plate
Brewster Plate
f QR
f
80 150 50
fiber bundle
10 X 30 W 80 150 50
fiber bundle
10 X 30 W
f
f
2f
f
f QRrelay optics f
2f
relay optics
f
54 mm laser rod
with two undoped
end caps
54 mm laser rod
with two undoped
end caps
• Isolator: Gsänger
GEO 600 Slave Laser
performance of the LIGOI frequency stab
High Power Locking Scheme
Medium Stage
• 12 W med. power stage
based on GEO 600 laser
design
opt ~ 30 %
• Isolator: Gsänger
high power design
GEO 600 Slave Laser Prototype II
Frequency Stability
6
1/2
Frequency Fluctuations [Hz/Hz ]
10
quasi monolithic slave
relative to stabilized NPRO
(inj.-lock actuator signal)
discrete component slave (ditto)
free running NPRO
relative to a reference cavity
5
10
4
10
3
10
2
10
1
10
0
10
-1
10
1
10
100
1000
Frequency [Hz]
10000
100000
12W injection-locked laser-system
• NPRO (non-planar ring
oscillator) master laser,
output power: 800mW
• slave laser optical
components mounted on rigid
resonator-spacer (Invar)
• 12W output power (< 5% in
higher TEM modes)
• injection-locking stable over
days
High Power Slave
• 87 W output power
• linear polarized
• single transverse mode
• M2x,y ~ 1,2
Output beam
30% OC
Input beam
( Master )
PZM
HWP
BP
QR
Experimental/Diode Temperature Control
PC
Hardwa re
In terlock
P T1 00
He at Sink
PT1000
Pel ti er
D/A Chang er
Photo-Diode
A/ D Chang er
Laser-Diode
Power
Supply
Light Bus
d igital
PID -Co ntro ller
Peltier
A mplifie r
laser diode JENOPTIK 30 W, fiber coupled, NA 0.22; 800 m
temperature resolution: 0.01K
temperature fluctuations: 2-3 digits
temperature stability better than 0.05K
Experimental/Diode Box
•4 boxes
user interface
4 systems (boxes)
• each 10 X 30 W fiber-coupled diodes
 1200
W pump Power
40 temperatures
4 current controls (1 per box)
laser diode (10)
heat sink (2)
ADC/DAC
upcoming:
• 40 diode power measurements
 laser power control for
each diode
overtemp interlocks
peltier drivers
High Power Locking Scheme
• 87 W high power slave
single transverse mode
M2 ~ 1,2
opt ~ 23 %
High Power Locking Scheme
PD

PD
FI
CCD
PMC
PD
PD
Modemaching
Output
beam

MISER
EOM

FI
Results
First high power injection locked laser system
87 W linear polarized, single frequency,
single transverse mode
( total power of all systems ~ 101 W )
total optical efficiency 22%
locking direct to 2 W master possible
single frequency output power ~ 70 W
Beam Characterization
Beat signals of free running slave
 no higher order modes detect
0,000015
Beam profile of locked system
 M2~1.1 , less elliptical beam
Res.Bandwith 50 KHz
PD Signal [V]
0,000010
0,000005
0,000000
2,00E+008 3,00E+008 4,00E+008 5,00E+008 6,00E+008 7,00E+008 8,00E+008
f [Hz]
Relock Time
2
1
Slave
12 W Master
Piezo Ramp:
Master 1,3 Hz (770ms)
Slave 2.5 Hz (400ms)
0
PD Signal [V]
-1
-2
-3
-4
-5
-6
-7
-8
-0,4
-0,3
-0,2
-0,1
0,0
0,1
0,2
0,3
0,4
t [s]
relock time < 500 ms
faster relock possible depending on piezo ramp
System Optimization
To get full injection locked power following things
has to be optimized:
• Modemaching in the high power slave
( FI with compensated thermal lens )
• Outputcoupler of high power slave
•optimize gain overlap of different Lasers
• implement pumplight optimization
next steps
Pump Concepts
mode selective pumping
10 x 30 W
Laser Rod
Glas Rod
Objektiv
4500
10
10
8
8
6
6
4000
3500
2000
Y
2500
Y
W/cm
2
3000
w = 1mm
1500
1000
4
4
2
2
500
0
20
40
60
80
100
x
2
4
6
X
8
10
2
4
6
X
8
10
Pump Light Homogenization
60
mulimode output power [W]
with Homogenization
w/o Homogenization
50
 30 % more output
power with
homogenization
 better gain overlap
and less distortion
for low order modes
40
30
20
10
0
20
40
60
80
100
120
140
Pump Power [W]
160
180
200
New Head Design
Pump Chamber
water flow
2.5 cm
Birefringence compensation
Find working point with less birefringence
Pump Light Homogenization
fiber bundle
laser crystal
FS- rod
optics
fluorescence w/o
homogenization
Homogenization of Pump Light
Glas Rod 3x30mm
8
8
6
6
Y
10 x 800 µm
10
Y
simulation
10
4
4
2
2
2
4
6
10
measured
30 x 800 µm
8
10
2
4
6
10
X
8
8
10
X
8
6
6
4
4
2
2
2
4
6
8
10
2
4
6
8
10
Pump Concepts
mode selective pumping
10 x 30 W
Glas Rod Laser Rod
Objektiv
9000
10
10
8
8
6
6
8000
7000
5000
4000
w = 2 mm
Y
Y
W/cm
2
6000
4
4
2
2
3000
2000
0
20
40
60
80
100
x
2
4
6
X
8
10
2
4
6
X
8
10
Optimization of Pump Light
Distribution
CCD
• alignment of homogenous and centered pump light profile
• pump power calibration for PD-readout
Optimize Resonator
20% OC
HR
20% OC
HR
Brewster Plate
Brewster Plate
f QR
f
80 150 50
fiber bundle
10 X 30 W 80 150 50
fiber bundle
10 X 30 W
f
f
2f
f
f QRrelay optics f
2f
relay optics
f
54 mm laser rod
with two undoped
end caps
54 mm laser rod
with two undoped
end caps
• Test different laser rods 4,5 mm
• Test different pump spot sizes
 find best laser design before doubling the system
Advanced Ligo Laser 1st. Step
20% OC
HR
20% OC
HR
Brewster Plate
Brewster Plate
f QR
f
80 150 50
fiber bundle
10 X 30 W 80 150 50
fiber bundle
10 X 30 W
f
f
2f
f
f QRrelay optics f
2f
relay optics
f
54 mm laser rod
with two undoped
end caps
54 mm laser rod
with two undoped
end caps
• Optimized laser head with respect to
beam quality and output power
• up to now 100 W of output power in
single transverse mode are demonstrated
Advanced Ligo Laser 2st. Step
output
f QR
f
BP
from Master
f QR
f
20% OC
HR
20% OC
HR
Brewster Plate
Brewster Plate
f QR
f
80 150 50
fiber bundle
10 X 30 W 80 150 50
fiber bundle
10 X 30 W
HR@1064
HT@808
f
2f
f
f
2f f
54 mm laser rod
f QRrelay optics f
with two undoped
end caps
2f f
54 mm laser rod
relay optics
with two undoped
end caps
f
Modeling/Overview
pump light distribution
Finite Element Method for
calculating
•temperature distribution
•mechanical stress
•deformation
•ray tracing
•analytical approximation
•experimental data
heat generation
gain
wave propagation through
inhomogenous medium
•finite differencing
•split step fourier approach
cooling
calculation of optical
properties
k-vector •thermal lens
•stress-induced birefringence
Model
3 mm diameter
54 mm length
assumption:
cylinder symmetrical pump light distribution
•model takes into account temperature dependent properties
wavelength dependent absorption coefficient
temperature dependent heat conducitvity
temperature dependent expansion coefficient
temperature dependent dn/dT
Fox/Li Approach
Iterative Solution of Kirchhoff integral equations
initial distributed E(x,y,z0)
(e. g. noise)
medium
free propagation
mirror/aperture
free propagation
•inhomogenous distributed gain,
refractive index, birefringence
concentrated in gain/phase sheets
•propagation between gain/phase
sheets and in free space described
by FFT propagator
medium
free Propagation
mirror/aperture
output power
beam quality
free Propagation
no
convergence ?
yes
Abberations/End Pumped vs.
Transversally Pumped
OPD, deviation from ideal lens
0,15
End Pumped
Transversally Pumped
OPD-OPDideal[m]
0,10
0,05
<10 nm
0,00
-0,05
-0,10
-0,2
0,0
0,2
0,4
0,6
0,8
r [mm]
1,0
1,2
1,4
1,6
Thermal Modeling/Temperature
Distribution
varying with pump spot diameter (pump power kept constant)
500 m
Thermal Modeling/Maximum
Temperature
Maximum Temperature vs. Pump Spot Radius
maximum temperature [°C]
140
130
120
110
100
90
80
0
1000
2000
3000
pump spot radius [m]
4000
5000
Von Mises Stress
varying with pump spot diameter (pump power kept constant)
500 m
Mechanical Stress/Von Mises
Equivalent Stress
varying with pump spot diameter (pump power kept constant)
Maximum Equivalent Stress vs. Pump Spot Radius
maximum equivalent stress [MPa]
150
140
130
120
110
100
90
80
70
60
50
40
0
1000
2000
3000
pump spot radius [ m]
4000
5000
Resumé
•Modeling
•100 W of output power will be achieveable
•abberations will have to be compensated for
•abberations are comparable in end pumped and transversally
pumped rod
•Experimental
•4 diode boxes have been set up (1200 W of pump power)
•temperature stabilization works
•pump light homogenization has been demonstrated
•45 W single mode and 75 W multi mode laser has been
demonstrated (single rod, no compensation)
alt. concept
Face-pumping vs Edge-pumping
Pumping
zig-zag
slab
Facepumping
zig-zag
plane
Cooling
Edgepumping
zig-zag
plane
Pumping
Cooling
Experimental Setup for 100W demonstration
10W LIGO
MOPA
System
Mode-matching
optics
ISOL
ATOR
Mode-matching
Output Power = 32 W
optics
20 W
Amplifier
Lightwave Electronics
Edge Pumped
Slab #1
Mode-matching
optics
Mode-matching
End Pumped Slab
optics
Output Power = 110 W
Edge Pumped
Slab #2
Pump Power = 300 W
Pump Power = 420 W
Output Power = 65 W
10W LIGO Laser
Characteristics:
• Single frequency.
• TEM00
• Narrow linewidth.
• Low frequency &
amplitude noise.
10W
Amplifier
400mW
NPRO
Nd:YAG Laser Head
3.8 cm
End pumped slab geometry
Motivation -> Higher efficiency
• Near total absorption of pump light.
808nm
Pump
undoped end
• Confinement of pump radiation leads
to better mode overlap
3.33cm
signal
OUT
1.51cm
1.51cm
0.6% Nd:YAG
signal
IN
808nm
Pump
undoped end
1.1mm X 0.9mm
What next for the 100W experiment?
10W LIGO
MOPA
System
Mode-matching
optics
ISOL
ATOR
Mode-matching
Output Power = 35 W
optics
20 W
Amplifier
Lightwave Electronics
Key: Improve absorption of pump
light and achieve
the expected small signal gain.
Edge Pumped
Slab #1
Mode-matching
optics
2-pass End
Pumped Slab
Pump Power = 230 W
Expected Output
Power = 100W
Scaling to 200 W : Experimental Plan
10W LIGO
MOPA
System
Mode-matching
optics
20 W
Amplifier
ISOL
ATOR
Pump Power = 130
Output TEM00Power = 50 W
Lightwave Electronics
2-pass End Pumped
Slab #1
Mode-matching
optics
2-pass End
Pumped Slab #2
TO PRE MODE
CLEANER
Pump Power = 430 W
Expected TEM00
Output Power = 160W
WBS plan
manpower
costing
the LIGOII laser-team
Laser Zentrum
Hannover
High-power solidstate-lasers design
Max-Planck Institut
University of Glasgow
University of Hannover
power and frequency
stabilization
Stanford
Adelaide
GEO600 pre-stabilized laser
LIGOII pre-stabilized laser
LIGO Lab
German
proposal