Download G020087-00

Status of 100 W Rod System at LZH
Ralf Wilhelm
Martina Brendel, Carsten Fallnich, Maik Frede,
René Gau, Herbert Welling, Ivo Zawischa
Laserzentrum Hannover e. V.
Hollerithallee 8
D-30419 Hannover
Germany
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Outline
Modeling
•Overview
•Results
Experimental results
•Integrated Diode Units
•Pump Optics
•Pre-Experiments
Resumé/Outlook
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
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
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
100 W Laser Head
HR 808 coating for double pass
3 mm diameter
54 mm length
•end-pumped rods
reduce thermal gradient in z-direction
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
100 W Laser Head
undoped end caps
3 mm diameter
54 mm length
•end-pumped rods
thermal lensing consists of two parts
thermal part via dn / dT
end effect (bulging of end surface)
reduced by
undoped endcaps
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
100 W Laser Head
90° quartz rotator
3 mm diameter
54 mm length
•end-pumped rods
•undoped endcaps reduce absolute temperature and thermal lens
•90° quartz rotator compensates for birefringence
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Model
3 mm diameter
54 mm length
assumption:
cylinder symmetrical pump light distribution
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Model
3 mm diameter
54 mm length
assumption:
cylinder symmetrical pump light distribution
•model takes into account wavelength/temperature dependent properties
wavelength dependent absorption coefficient
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Model
3 mm diameter
54 mm length
assumption:
cylinder symmetrical pump light distribution
•model takes into account wavelength/temperature dependent properties
wavelength dependent absorption coefficient
temperature dependent heat conducitvity
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Model
3 mm diameter
54 mm length
assumption:
cylinder symmetrical pump light distribution
•model takes into account wavelength/temperature dependent properties
wavelength dependent absorption coefficient
temperature dependent heat conducitvity
temperature dependent expansion coefficient
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Model
3 mm diameter
54 mm length
assumption:
cylinder symmetrical pump light distribution
•model takes into account wavelength/temperature dependent properties
wavelength dependent absorption coefficient
temperature dependent heat conducitvity
temperature dependent dn/dT
temperature dependent expansion coefficient
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Model
3 mm diameter
54 mm length
assumption:
cylinder symmetrical pump light distribution
•model takes into account wavelength/temperature dependent properties
wavelength dependent absorption coefficient
temperature dependent heat conducitvity
temperature dependent expansion coefficient
temperature dependent dn/dT
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Thermal Modeling/Temperature Distribution
•solution of time independent heat conduction equation by FEM (ANSYS)
1/4 of rod for
symmetry reasons
20.1°C
83.7°C
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Mechanical Stress/Von Mises Equivalent
Stress
•fracture limit for YAG 130 thru 260 MPa
0.0 MPa
41.3 MPa
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Thermal Lens/Abberations
d2
D(r )   2 OPD (r ,  )
dr
L
Opt . Path   dz n( x, y, z; T )
0
28
Optical Path Difference, 250 W
26
OPD, deviation from ideal lens
Thermal lens 7.0 m
-1
0,10
OPD-OPDideal[m]
OPD [m]
0,15
24
22
20
18
-0,2
OPD
parabolic fit
0,0
0,2
0,4
0,6
0,8
1,0
0,05
0,00
1,2
-0,05
1,4
1,6
r [mm]
-0,10
-0,2
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
r [mm]
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
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
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
First Results
test resonator (plane-plane)
•mode diameter in rod 1 mm
O.C.
L1
L2
L3
20
apertures
-4.0 Diopters
Output Power [W]
L1=10 mm
L2=100 mm
L3=400 mm
15
10
5
0
90
100
110
120
130
140
Pump Power [W]
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
First Results
2.188E-4 -- 2.5E-4
1.875E-4 -- 2.188E-4
1.563E-4 -- 1.875E-4
1.25E-4 -- 1.563E-4
9.375E-5 -- 1.25E-4
6.25E-5 -- 9.375E-5
3.125E-5 -- 6.25E-5
0 -- 3.125E-5
20
Output Power [W]
100 W
Y Axis
150
15
10
5
0
100
100
150
150
120 W
X Axis
Y Axis
2.625E-4 -- 3E-4
2.25E-4 -- 2.625E-4
1.875E-4 -- 2.25E-4
1.5E-4 -- 1.875E-4
1.125E-4 -- 1.5E-4
7.5E-5 -- 1.125E-4
3.75E-5 -- 7.5E-5
0 -- 3.75E-5
100
100
150
X Axis
90
100
110
120
130
140
Pump Power [W]
•polarisation eigenstates
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
First Results/Birefringence Compensation
test resonator (plane-plane)
O.C.
L1
50
L2
L3
40
apertures
L1=10 mm0,0020
L2=100 mm -4.0 diopters
L3=400 mm
Z Axis
0,0015
Output Power [W]
quartz rotator
30
20
10
0,0010
0
0,0005
45
50
55
60
65
Pump
150 Power per Rod [W]
0,0000
100
xis
XA
xis
YA
150
©LZH
100
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
First Results/100 W Head
80
75
70
0,0010
60
55
0,0008
50
45
0,0006
Z Axis
Output Power [W]
65
40
35
0,0004
30
0,0002
25
20
225
0,0000
200
230
235
240
Pump Power per Rod [W]
300
245
250
xis
XA
xis
YA
300
200
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
First Results/100 W Head w/o Abberations
Output Power vs. Pump Power
250
200
150
0,004
100
50
0
220
225
Intensity [arb. units]
Output Power [W]
0,005
Data: AUS69_F
Model: gaussstr
Chi^2 = 1.3554E-10
wnull 555.9773
a
0.00433
xnull
0
±0
±0.52207
±3.5139E-6
0,003
2
M <1.05
0,002
0,001
230
235
240
Pump Power per Rod [W]
0,000
-4000
-3000
-2000
-1000
0
1000
2000
3000
4000
distance from optical axis [m]
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
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
1,0
1,2
1,4
1,6
r [mm]
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
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
8
10
2
4
6
8
10
X
X
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
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
8
10
2
X
4
6
8
10
X
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Homogenization of Pump Light
Glas Rod 3x30mm
simulation
10
8
8
6
6
Y
Y
10 x 800 µm
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
©LZH
10
2
4
6
8
10
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Thermal Modeling/Temperature Distribution
varying with pump spot diameter (pump power kept constant)
5000 m
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Thermal Modeling/Temperature Distribution
varying with pump spot diameter (pump power kept constant)
2000 m
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Thermal Modeling/Temperature Distribution
varying with pump spot diameter (pump power kept constant)
1500 m
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Thermal Modeling/Temperature Distribution
varying with pump spot diameter (pump power kept constant)
1000 m
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Thermal Modeling/Temperature Distribution
varying with pump spot diameter (pump power kept constant)
750 m
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Thermal Modeling/Temperature Distribution
varying with pump spot diameter (pump power kept constant)
500 m
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Thermal Modeling/Maximum Temperature
Maximum Temperature vs. Pump Spot Radius
maximum temperature [°C]
140
130
120
110
100
90
80
0
1000
2000
3000
4000
5000
pump spot radius [m]
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Von Mises Stress
varying with pump spot diameter (pump power kept constant)
5000 m
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Von Mises Stress
varying with pump spot diameter (pump power kept constant)
2000 m
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Von Mises Stress
varying with pump spot diameter (pump power kept constant)
1500 m
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Von Mises Stress
varying with pump spot diameter (pump power kept constant)
1000 m
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Von Mises Stress
varying with pump spot diameter (pump power kept constant)
750 m
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Von Mises Stress
varying with pump spot diameter (pump power kept constant)
500 m
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
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
4000
5000
pump spot radius [m]
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
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
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
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
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Pump Chamber
water flow
2.5 cm
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Pre-experiments
laser rod
pump optic
TR
75
70
multimode
65
60
PL [W]
55
50
45
40
35
M2 < 3
30
25
140
160
180
200
220
240
260
PD [W]
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Birefringence Compensated Resonator
Faraday Rotator
thermal lens image
Faraday
Rotator
FR
laser rod
TR
pump optic
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
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)
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2
Outlook
•optimize overlap of pump light distribution and mode diameter
•compare calculated abberations to experiment (Shack-Hartmann sensor,
diploma thesis P. Huke)
•evaluate conductive cooling (coating of rod‘s shell)
-reduce abberations (lower absolute temperature)
-avoid contact of cooling fluid with rod
•compensate for abberations
?
©LZH
Livingston, La.; 22-03-2002
LIGO-G020087-00-2