thermal headaches in advanced ligo input optics
DESCRIPTION
Thermal Headaches in Advanced LIGO Input Optics Guido Mueller, Rupal Amin, David Guagliardo, David Tanner, and David Reitze Physics Department University of Florida Gainesville, FL. LIGO-G010130-00-Z. Input Optics Functions. RF Modulation Mode Cleaning Mode Matching Optical Isolation - PowerPoint PPT PresentationTRANSCRIPT
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Thermal Headaches in Advanced LIGO Input Optics
Guido Mueller, Rupal Amin, David Guagliardo, David Tanner, and David Reitze
Physics Department
University of Florida
Gainesville, FL
LIGO-G010130-00-Z
2
Input Optics Functions
•RF Modulation
•Mode Cleaning
•Mode Matching
•Optical Isolation
•Distribution of Control Beams
•Self Diagnostics Conceptual layout of IO optical
components
Faraday Isolation
ModeMatching Telescopeinto ModeCleaner
Mode
Mode Matching and Beam Steering Telescope intoCore Optics
FaradayIsolation
ISC Wavefront Sensing
IFO Control to ISC
Intensity Stabilization
COC
to PSL
RFModulation
Stabilizationfrom ISC
Stabilizationto PSL
PSL
RFAM monitor
Cleaner
to steering mirrors
steeringmirrors
VariableAttenuator/Fast Shutter
Diagnostics
Parameter LIGO I Advanced LIGO
Laser Power 8.5 W 180 W (150 W)
Overall IO
Efficiency (TEM00)
75% 66%
Optical Isolation 70 dB (> 85 dB)
3
Advanced LIGO will operate at 180W CW powers - “presents some challenges”:
•Thermal Lensing --> Modal Degradation
= z = 1 + i
•Thermally induced birefringence
-FI- loss of isolation-EOM - spurious amplitude modulation
•Damage
•Other (nonlinear) effects (SHG, PR)
The Challenge
LiNbO3 at 30W:
5 x 5 x 40 mm LiNbO3 EOM - thermal lensing is:
i) severeii) position dependent
L P / 2 K dndT
EzME�
,~
4
Characterization of thermal lensing
50 W Nd:YLF
HRM
HRM HRM
Beam Dump
Power Meter
/2
/4
HRM
Glan Pol.
Lensing Measurement
HRM
Beam Dump
Power Meter
/2
/4
HRM
Glan Pol.
Sag Measurement
Beam Scan
DM
DM
NeNe
PD - Signal
PD -Ref.
Sample
Sample
= 1053 nm
z
Samples:
TGG: Litton [111] 10 mm diameter, 20 mm length
LiNbO3: Leysop, 5 x 5 x 40 mm
5
Optical Path Difference Measurements
P=50 WAbsolute L (hot - cold): 10 mOPD (1/e intensity): ~ 100 nm 250 nm @ 125W
Theory: Hello-Vinet
6
Optical Path Difference Measurements
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Thermal Lens Magnitude (waves)
Tw
o-D
ime
nsi
on
al
Po
we
r C
ou
pli
ng
,
TEM00 with focus compensation
TEM00 without focus compensation
TEM02 without focus compensation
TEM04 without focus compensation
Mansell, et al., Appl. Opt., 2001
dxxxc aberratedmmaberratedx )()(),( *
yxnaberratedynaberratedymaberratedxmaberratedx cccc ),(),(),(),( **
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Propagation Measurements I
w(z)
0 500 1000 1500 20000.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
100 W - h
Laser/pol
Laser/pol/TGG
Laser only
Bea
msi
ze (
mm
)
Propagation Distance (mm)
0 500 1000 1500 20000.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2100 W - v
Laser/pol/TGG
Laser/pol
Laser only
Bea
msi
ze (
mm
)
Propagation Distance (mm)
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Propagation Measurements II
0 50 100 150 200
0
5
10
15
20
25
vert
hor
Fo
cal L
eng
th (
m)
Input Power (W)
fv= WP
m233
fh= WP
m174
Effective Thermal Lens
50 W
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Thermal Lensing in LiNbO3
EOM 1 EOM 2 EOM 3180 W
•KTP does work; 300 W CW power, 1064 nm (H. Injeyan, TRW); RTA should also work (lower loss tangent)
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E-O Modulation in Advanced LIGO
Alternative Method: Mach-Zehnder modulation --> architecture problem
PM 2 PM 3
f0
Im [V(t)]Re [V(t)]
SpectrumAnalyzer Optical
R=90%T=10%
R=10%T=90%
G
f0
PM 1
Prototype developed for initial LIGO detectors, but not well characterized >> R&D effort
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Power Independent Compensation of Thermal Lensing
...
),(
...
~
~
0
1
2
0
zMTEM
TEM
.........
...
...
),(//
/
25
2
23
23
2
2
2
2
1
zz
iz
i
z
zM
dndT
L P / 2 K
z = 1 + i
dndT
= absorption coefficient
K = thermal conductivity
......
~
~
2
0
0
1
TEM
TEM
M-1(, z)
dndT
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0.0 0.2 0.4 0.6 0.8 1.0
0.80
0.82
0.84
0.86
0.88
0.90
0.92
0.94
0.96
0.98
1.00
Rem
ain
ing
TE
M00
Separation Distance (m)
Thermal Lensing Compensation
Modeled using Melody
FI or EOM
Parameter TGG FK51
(m-1) 2 x 10-1 1 x 10-1
K (W/m K) 7.4 0.9
dn/dT (C-1) + 2 x 10-5 -6 x 10-6
Length (mm) 20 15.9
150 W
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Thermal Lensing Telescope
Similar to current LIGO Telescope• 2 mirror design (vacuum envelope constraints)• Accommodates wide range of mode matching parameters• All large (20 cm) optics
• in-situ adjustment with feedback
0.8
0.95
0.9
0.7
Dev. from Nom. Waist Position (m)
Wai
st S
ize
(cm
)
Wide Bandgap Glass
1064 nm
532 nm
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R&D Issues Still to be Faced
• Modulator Development: • RTA performance• MZ modulation
• Isolator Development:• Full FI system test (TCFI, EOT)• Possible thermal compensation (-dn/dT materials)
• Telescope Development:• in-situ mode matching adjustment