parametric effects in a macroscopic optical cavity
DESCRIPTION
AIGO. Parametric Effects in a Macroscopic Optical Cavity. Sascha Schediwy [email protected]. AIGO Workshop Thursday 6 th October. Optical Spring. Circulating Power. Frequency. Q reduction Q increase. Q Increase - Parametric Gain. Niobium Resonator. Cavity Properties Niobium - PowerPoint PPT PresentationTRANSCRIPT
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Parametric Effects in aParametric Effects in aMacroscopic Optical CavityMacroscopic Optical Cavity
Sascha [email protected]
AIGO WorkshopThursday 6th October
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Optical SpringOptical Spring
CirculatingPower
l
cFSR
2
)2( 22 LRc
PF circ
rad
Frequency
Q reduction Q increase
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Q Increase - Parametric GainQ Increase - Parametric Gain
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Niobium ResonatorNiobium Resonator
Cavity Properties Niobium Qm = 1.562 (8)*105
fmech = 780 Hz
meff = 32.3 g
l = 0.10 m
Proxy Mirrors R = 0.98 F = 155 roc = 10.0 m
Super Mirrors R ~ 0.99968 (rated: 0.9994+) F ~ 9800 (rated: 5200+) roc = 1.0 m
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60°C
Yacca Gum PropertiesYacca Gum Properties
viscous at 80°C+ reversible bonds dissolves in alcohol relatively low loss Q ~ 100
70°C80°C90°C
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Yacca Gum BondingYacca Gum Bonding
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Experimental DesignExperimental Design
3525
temp mirror 1
temp mirror 2
key:objectposition (mm)beam power (%)optical loss (%)
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Optical Error Signal RingdownOptical Error Signal Ringdown
Ringdown Linear Fit
time (s) time (s)
(experimental results)
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Q Factors
0.60
0.62
0.64
0.66
0.68
0.70
0.72
0.74
0.76
0.78
0.80
779.
68 -
3
779.
68 -
4
779.
68 -
5
779.
68 -
6
779.
68 -
7
779.
68 -
8
779.
68 -
9
Ave
rage
Mode Frequency (Hz)
Qu
alit
y F
acto
r (1
0^5)
Quality Factor Quality Factor
Q = 0.700 ± 0.002 x105
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Proxy Mirror Q ModificationProxy Mirror Q Modification
Mechanical Q
Quality Factor (-)
F[rad] (N)
k[opt] (N/m)
Modified Q
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Super Mirror Q ModificationSuper Mirror Q Modification
F[rad] (N)
k[opt] (N/m)
(Hz)
(Hz)
(Hz)
Quality Factor (-)
Laser Maximum
Damage Threshold Limited
Mechanical Q
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Parametric Instability TranquilisationParametric Instability Tranquilisation
Model proposed by:
Braginsky & Vyatchanin
(Phys. Lett. A 293 (2002) 228-234)
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Any Question?Any Question?
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Q Modification / Optical Spring Const.Q Modification / Optical Spring Const.
2232
181
1
21
11024
cR
fRlRRc
fPlk
offset
offsetinputopt
1
32543
2
21
8121
40961
Rc
flRfcm
lfP
offsetmecheff
offsetinput
mechalt
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Circulating PowerCirculating Power
Cavity Properties Rayleigh Range / Beam Waist
R1 = R2 = 1.0 m
L = 0.1 m
Spot Size at Mirror ( z = 0.05 m )
2
20
22 z
zzR
1
20
11 z
zzR
20
22
22 4
2
1
2zR
Rz
20
21
21 4
2
1
2zR
Rz
4
20
LLRz
mz
w 400 10716.2
mz
zwzw 4
2
00 10787.21)(
mz 2179.00
24
282
10767.7
10767.7)(
cm
mzw
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Circulating PowerCirculating Power
Newport Supermirrors Damage Threshold:
Maximum Circulating Power:
Maximum Input Power R1 = R2 > 99.94%
T1 > 0.06%
242 10767.7)( cmzw
2/1000 cmWDT
WP Maxcirc 7767.0)(
)(
1
2
21)(
1MaxcircMaxin P
T
RRP
mW
P Maxcirc
466.0
0006.0 )(
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Radiation Pressure ForceRadiation Pressure Force
Radiation pressure force for FP Cavity
)2( 22 LRc
PF circ
rad
≈ unity
inx
irad P
eRRc
TLRF 24
21
122
1
)2(
inx
icirc P
eRR
TP 24
21
1
1
dx
xFdk rad
opt
)(
inx
iopt P
ceRR
TLR
dx
dk 24
21
122
1
)2(
21 iCx
opteB
A
dx
dk
let:c
PTLRA in122 )2(
21RRB
4
C
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Optical Spring ConstantOptical Spring Constant
21 iCx
opteB
A
dx
dk
21 BeeB
A
dx
dk
iCxiCxopt
substitute ABC back
221 BCxBCos
A
dx
dkopt
2221
sin2
BCxBCos
CxABCkopt
2
2121
21221
4cos21
4sin28
xRRRR
xRRLRT
c
Pk in
opt
2
2121
21221
4cos21
4sin28
cflRRRR
cflRRLRT
c
Pk
offset
offsetinopt
in x space
in f space
mWP Maxin 466.0)(
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Cavity AlignmentCavity Alignment
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–ωm ωm
““Low Q” / “High Q”Low Q” / “High Q”
FWHM
FWHM
–ωm ωm
Low Q – when the bandwidth is larger than ωm
High Q – when the bandwidth is smaller than ωm