Squeezed light in present and future GW observatories · Alexander Khalaidovski Squeezed light in...

Squeezed light in present and future GW observatories Alexander Khalaidovski 1

Squeezed light

in present and future GW observatories

Alexander Khalaidovski for the AEI Quantum Interferometry group

(Roman Schnabel)

13th Marcel Grossman Meeting – MG13 – Stockholm University

Albert Einstein Institute

Max Planck Institute for Gravitational Physics

Institute for Gravitational Physics of the Leibniz University Hannover

http://www.qi.aei-hannover.de

Squeezed light in present and future GW observatories Alexander Khalaidovski 2

ET sensitivity curves

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Coherent state

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Michelson interferometer – bright port

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Vacuum state (0-point fluctuations of EM field)

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Origin of the quantum noise

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Squeezed vacuum state

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Injecting squeezed vacuum

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How to do?

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Generation of squeezing

LiNbO3 or

PPKTP

BASED ON OPTICAL PARAMETRIC AMPLIFICATION (OPA)

Squeezed field:

Pump field: 532 nm cw

1064 nm cw

For GW observatories

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squeezed-light lasers for

GW observatories

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The GEO 600 squeezed-light laser

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LIGO-H1 squeezed-light laser

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Requirements

Squeezing in earth-bound GW detection band

(10 Hz – 10 kHz)

Stable control scheme

(allowing for long-term, independent operation)

Strong squeezing

Squeezed light in present and future GW observatories Alexander Khalaidovski 15

Squeezing spectrum

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Loss sources

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Loss sources

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Squeezing available for injection

maximal directly observed squeezing: 9.6 dB

up to 11.5 dB available for injection

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Squeezing spectrum

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Available well below 10 Hz

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Long-term stability (automated exp. control)

Khalaidovski et al., Class. Quantum Grav. 29 (2012) 075001

duty cycle: 99.93 %

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squeezed-light lasers are ready

the message concerning squeezed-light lasers

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State-of-the-art

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squeezing in GW observatories today

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Squeezing-improved GEO 600 sensitivity

The LIGO Scientific Collaboration, Nature Phys. 7 (2011) 962-965

Factor 1.5

sensitivity improvement

Up to 3.5 dB

detected squeezing

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H. Grote @ March LVC Meeting (MIT)

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H1 with squeezed light

• 2.25 dB squeezing

enhancement

• squeezing

observable down to

100 Hz

• no noise added at

lower frequencies

• inspiral range

improved by 1 Mpc

Courtesy Lisa Barsotti for the LIGO Scientific Collaboration

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the future

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Einstein Telescope

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Einstein Telescope

Goal: 10 dB squeezing detected

total allowed optical loss: 10 %

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Loss sources

- Faraday isolators

- polarization optics

propagation loss, especially:

escape efficiency of the squeezed light source

detection loss

non-perfect mode-matching

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Squeezing injection

ˆ X 1

ˆ X 2

Quantum noises

Shot-noise

dominated

Radiation

pressure noise

dominated

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Filter cavities

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Remaining challenges

very low round-trip loss required

deviation from design parameters

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Filter cavities

Squeezed light in present and future GW observatories Alexander Khalaidovski 36

Remaining challenges

very low round-trip loss required

mode-matching

deviation from design parameters tunable loss

filter cavity length control scheme (detuned from resonance!)

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Conclusions

Squeezing is already used in the first detector generation (GEO 600, H1)

Squeezing will become a ‚standard‘ technique in future detector

Optical loss is squeezings‘ biggest enemy!!!

- better AR coatings

- lower crystal absorption

- lower propagation loss

(mainly polarization optics)

} higher squeezing contribution

generations

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thank you

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Experimental layout (scaled to reality)

• Breadboard: 113x135 cm

• Main Laser: InnoLight Mephisto

> 120 opt. components

• Aux. Lasers: Mephisto OEM

total weight ≈ 120 kg

• Optics: ATF (superpolished)

• Nonlinear medium: PPKTP

• Beam height: 50mm

• Compact design

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LIGO-SQUEEZER

• generally similar to AEI device

• main differences:

- „off-the shelf“ optics used

- requires more space, beam height 4´´

- no cleanroom environment

higher stray light contribution

- no fast data acquisition channels

- SHG design

- doubly-resonant (1064 nm and 532 nm)

- bow-tie configuration

additional 42 dB isolation

- LO beam from PSL via fiber

excess phase noise, no MC

• AEI contributions

- balanced homodyne detector

(- control scheme)

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Control scheme for audio-frequency squeezing

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Origin of the quantum noise

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Loss sources

r=T

T + L

escape efficiency of the squeezed light source

Absorption

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Loss sources

escape efficiency of the squeezed light source

propagation loss (Faraday isolator, pol. optics, coatings)

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Loss sources

escape efficiency of the squeezed light source

propagation loss

detection loss (photo diodes, homodyne fringe visibility)

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Loss sources

escape efficiency of the squeezed light source

propagation loss

detection loss

< total loss during characterization: 10.5 %

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how much squeezing can we inject in

GEO 600?

Injection of squeezed light

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Sensitivity to optical loss

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Sensitivity to optical loss

maximal squeezing: 9.6 dB

total identified loss: 10.5 %

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Implementation in GEO 600

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Optical loss

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Expected squeezing impact

due to loss from injection to detection

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near future

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Next steps at GEO HF

• OMC

• propagation

reducing losses

• mode-matching } ca. 22 %

seem feasible

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Goal

6 dB detected squeezing

Factor 2 sensitivity improvement