S. Chelkowski Slide 1WG1 Meeting, Birmingham 07/2008
Overview Quantum noise in gravitational wave detectors
Generation of squeezed states
Using squeezing in a gravitational wave detector
Frequency dependent squeezing
Generation of squeezing in the gravitational wave frequency band
Best squeezing measurements so far
Squeezed light in GEO600
S. Chelkowski WG1 Meeting, Birmingham 07/2008 Slide 2
A simple gravitational wave detector
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Quantum noise limited sensitivity
Shot Noise Radiation Pressure Noise
factor 100 in power= factor 10 in sensitivity= factor 1000 in event rate
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Squeezed light enhanced interferometer
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Squeezed light enhanced interferometer
20dB of squeezing= factor 10 in sensitivity= factor 1000 in event rate
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Amplitude-Quadrature
Phase-Quadrature
Heisenberg uncertainty relation
An explanation of squeezing
coherent state
squeezed state
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Vacuum Noise
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Squeezed Vacuum
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• Strong interaction between seed- and pump field
• MgO:LiNbO3 – crystal as nonlinear material
• Phase matching via temperature
• Fractions in phase get amplified, out of phase deamplified
OPA - optical parametric amplification
1064nm532nm
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• MgO:LiNbO3 2 x 2.5 x 6.5mm• 7% doping• bikonvex or plane/konvex rc=8mm• coatings @ 1064 and 532nm
Side A: AR (R < 0.05%)Side B: HR (R > 99.98%)
• hemilithic Resonator @ 1064nm coupling mirror R = 96.7%Finesse = 180
FSR = 3.9GHz• phasematching temp. ~65°C• temp. stabilized via peltier elements
New oven design
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Dark Noise
Broadband squeezing up to 30MHz
Relaxation oscillation of the Laser
Vacuum noise
Squeezing results from a normal OPA
Squeezing in a real gravitational wave detector
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GEO600
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Quantum noise in GEO600
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Reducing the quantum noise
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amplitude squeezing
Reducing the quantum noise
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Reducing the quantum noise
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Effect of a detuned filter cavity
Squeezed Vacuum Interaction with a cavity
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amplitude squeezing
+45°-45°
Reducing the quantum noise
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Reducing the quantum noise
Frequency-dependent squeezed light
How can we create it?
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Chelkowski et al.,PRA 71, 013806 (2005)
Frequency-dependent squeezing
Detuned locked to +15MHz
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Chelkowski et al.,PRA 71, 013806 (2005)
Squeezing
Vacuum Noise
Anti-Squeezing
Phase quadrature
Amplitude quadrature
Frequency-dependent squeezing
A rotating squeezing ellipse – FC detuning +15MHz
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Chelkowski et al.,PRA 71, 013806 (2005)
A rotating squeezing ellipse – FC detuning +15MHz
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Chelkowski et al.,PRA 71, 013806 (2005)
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Chelkowski et al.,PRA 71, 013806 (2005)
+15 MHz -15 MHz
Angle of the squeezing ellipse
Generation of squeezed light on the gravitational wave frequency
band
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Generic squeezing from an OPA
Dark Noise
broadband Squeezing up to 30MHz
Relaxation oscillation of the Lasers
Vacuum noise
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• Seed field carries technical noise from the laser.
• Technical noise is imprinted onto the squeezed field.
• Seed field is needed for the generation of error signals.
OPA – optical parametric amplification
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Seed field is a control field
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OPA without seed turns into an OPO
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Setup for low frequency squeezing
homodyne angle
squeezing angle
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Setup for low frequency squeezing
homodyne angle
squeezing angle
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Setup for low frequency squeezing
homodyne angle
squeezing angle
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Setup for low frequency squeezing
homodyne angle
squeezing angle
Measured vacuum noise
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vacuum noise for 176µWvacuum noise for 88µWvacuum noise for 44µW
3dB3dB
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Measured squeezed vacuum noise
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vacuum noise for 88µW
squeezed vacuum noise
Chelkowski et al., PRA 75, 043814 (2007)
~6dB
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Squeezed vacuum enhanced Michelson interferometer
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Best squeezing measurements so far
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Optical layout
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Vahlbruch et al. PRL 100, 033602 (2008)
Measured squeezing
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Vahlbruch et al. PRL 100, 033602 (2008)
Squeezed light in GEO600
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GEO HF: Detuned Signal Recycling
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GEO HF: Tuned Signal Recycling
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Do we need a filter cavity?
Conclusion
Squeezed light can be used to reduces the quantum noise in gravitational wave detectors
Reflection at a detuned cavity creates frequency dependent light
Without a filter cavity, tuned signal recycling is the best choice
All needed techniques for the implementation of squeezed light into a gravitational wave detector are developed
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Appendix
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GEO 600 Layout
GEO 600:
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3dB SQZ:
6dB SQZ:
GEO HF Layout: short 8m Filter Cavity
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3dB SQZ:
6dB SQZ:
GEO HF Layout: long 1200m Filter Cavity
