test mass dynamics with optical springs proposed experiments at gingin chunnong zhao (university of...
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Test mass dynamics with optical springsproposed experiments at Gingin
Chunnong Zhao
(University of Western Australia)
Thanks to
ACIGA members
Stefan Danilishin and Farid Khalili
(Moscow State University)
Yanbei Chen
(Caltech)
GWADW2010, May 19, 2010
2GWADW2010, May 19, 2010
Contents:
• Gingin high optical power research facility
• 3-mode optomechanical transducer
• Test mass dynamics with double optical springs (negative optical inertia)
• Summary
3GWADW2010, May 19, 2010
Gingin high optical power test facility
High optical power is necessary for improving advanced detector sensitivity, but it also introduces thermal lensing and various instabilities.
4GWADW2010, May 19, 2010
Gingin high optical power test facility
On this facility, we have demonstrated:• Thermal lesing and thermal compensation• In-situ real time thermal lensing monitoring using
Hartmann sensor• 3-mode opto-acoustic interactions• Cavity locking using ultra-low frequency vibration
isolators
Current main focus: parametric instability and its control
GWADW2010, May 19, 2010 5
Future 80m interferometer
M1 M2
M3
To Detector Bench
South Fabry-Perot Cavity
East Fabry-Perot Cavity
Mode Cleaner
Nd:YAG laserl = 1064nm
East-end Station
South-end Station
NN
Signal Recycling Mirror
Beam Splitter
Power Recycling Cavity
6GWADW2010, May 19, 2010
Currently, 2 independent 80m cavities
South arm: Sapphire test masses with LIGO SOS suspension
Finesse, ~1300, 10 W laserTested thermal lensing and thermal compensation;Observed 3-mode opto-acoustic interactions;Study 3-mode optomechanical transducer.
East arm: Fused silica test masses with UWA isolators and suspensions
Nominal cavity finesse, 1500050W laser to be installed in August
Main goals are test the parametric instability and its control.
7GWADW2010, May 19, 2010
3-mode optomechanical transducer
m
10
Test mass internal mode wmCavity Fundamental mode (TEM00, frequency wo)
Input light frequency wo
Scattering into TEMmn,frequency w1
frequency matching and spatial overlap of acoustic and optical modes
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FSR
w
01
23
45
DwTEM
3-mode optomechanical transducer
w0
w0 +wm
DwTEM
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CO2 laser thermal tuning the radius of curvature
Sapphire test mass
Hartmannsensor
He-Ne laser
CO2 laser
Probe beam(800nm) Vacuum
tank
Vacuum pipe
Nd:YAGlaser
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CCD
Laser
ITM
CP
ETM
SpectrumAnalyzer
yx
QPD
Fundamental mode
High order mode
3-mode optomechanical transducer
CO2 Laser
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181.57 181.58 181.59 181.6 181.61 181.62 181.63 181.64 181.65 181.66
10-17
10-16
kHz
m/rtHz
GWADW2010, May 19, 2010
Test mass thermal noise at ~181.6 kHz
3-mode optomechanical transducer
0 50 100 150 200 250 300-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
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3-mode optomechanical transducerpotential to observe the quantum radiation pressure noise
Laser
1mm x 1mm x 50nm
The vibration of silicon nitride membrane excites high transverse optical mode
QPD
Finesse=10,000Meff=40 ng, T=4 k, wm=2p*200 kHzQm=106
Circulating power= 0.5W
Radiation pressure noise ~ thermal noise@ mechanical resonance
13GWADW2010, May 19, 2010
Test mass dynamics with optical springs
Motivation:
The SQL in terms of GW strain sensitivity:
A system with larger mechanical susceptibility (/m) has smaller SQL than the free mass SQL
Y. Chen, et al, LIGO-T1000069-v1
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Test mass dynamics with optical springs
Considering the test mass dynamics with double optical springs (DOS)
F is the force applied on the test mass, x is the displacement ,
,Here, s=-i;
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Test mass dynamics with optical springs
PM: power recycling mirror; PBS: polarization beam splitter; BS: beam splitter; PD: photodetector; ITM: input test mass; ETM: end test mass.
Driving force
This is achievable at Gingin with a 3-mirror cavity:
The same configuration can also be used to demonstrate the local readout (optical bar)
16GWADW2010, May 19, 2010
Test mass, m=0.8 kg, cavity length L=80m, cavity circulating power:I1= 3kW, I2=10kW,
Cavity detuning:1/2=200 Hz2/2=-500 Hz
Cavity linewidth:1/2 =36 Hz;2/2 =400 Hz;
Test mass dynamics with optical springs
Free mass
With DOS
17GWADW2010, May 19, 2010
Summary
Gingin high optical power research facility consists:• High power lasers• Advanced vibration isolators and test mass suspension• High finesse cavities
In addition to the parametric instability research, we propose to study:• High sensitivity optomechanical transducer (potential for detecting the quantum radiation pressure noise)• Optical negative inertia • Local readout (optical bar)