1. Progress toward squeeze injection in Enhanced LIGO
Gravitational wave detectors
Squeeze-enhanced AdLIGO
Nergis LVC, September 2009
LIGO-G

2. Advanced LIGO with squeeze injection
Radiation pressure
Shot noise
Power higher by 4x OR
6 dB squeeze injection

3. Quantum Noise in an Interferometer
Radiation pressure noise
Quantum fluctuations exert fluctuating force  mirror displacement X1 X2
Laser X1 X2
Shot noise limited  (number of photons)1/2
Arbitrarily below shot noise X1 X2 X1 X2
Vacuum fluctuations
Squeezed vacuum

4. Squeezed state generation

5. How to squeeze?
My favorite way
A tight hug

6. Squeezing injection Second harmonic generator (SHG) Laser
Convert 1064 nm  532 nm with ~50% efficiency
Optical parametric oscillator (OPO)
Few 100 mW pump field (532 nm) correlates upper and lower quantum sidebands around carrier (1064 nm)  squeezing
Balanced homodyne detector
Beat local oscillator at 1064nm with squeezed field
Laser
IFO
OPO
Faraday rotator
ASPD
SHG

7. Squeezed injection in LIGO (after S6)

8. Goals of H1 test
Inject 6 dB of squeezing into the antisymmetric (AS) port of H1
Measure 3 dB of improved SNR at frequencies where interferometer is shot noise limited
Ensure that no deleterious effects at all other frequencies in detection band
Low noise performance test is remaining critical step to implementation in Advanced LIGO

9. The H1 squeezer components
Initial LIGO 10 W MOPA pumps…
AEI-designed SHG  300 to 500 mW of 532 nm (green)
ANU-designed and built traveling wave OPO
LIGO-designed and built electronics
Integration and testing at MIT and LHO

10. Control System Interferometer S0 Fiber (PSL) Faraday S4 Laser 0 SHG
Homodyne Detector
Faraday S4
Laser 0
SHG
OPO S3 S1 S5 S2
OMC
Auxiliary
Laser 1
AS Port
Squeezer DC 10

11. Servo Model S0 Frequency lock Laser 0 to PSL using FSS
S1  Frequency lock Laser 1 (auxiliary ) to Laser 0 using FSS
S2  Phase lock Laser 1 to green light using feedback to PZT & Laser 1 additive offset
S3  Phase lock squeeze angle to AS port light using feedback to PZT & Laser 0 additive offset (LO lock)
S4  Lock SHG to Laser 0 with PDH to cavity PZT
S5  Lock OPO to green with PDH to cavity PZT

12. Simulink Model
LIGO-T v1
Sigg, Dwyer et al.

13. Fiber Stabilization not needed
Servo Model
Servo
Description
Bandwidth
Crossover
Laser 0
500kHz
10kHz 1
Laser 1 2
Coherent field
100kHz
~2kHz 3
Local oscillator 4
SHG length
~1kHz — 5
OPO length
Fiber Stabilization not needed
Laser 0 is frequency locked to main interferometer laser (PSL) and phase locked to AS port light

14. Noise couplings

15. Noise Model Highlights
Acoustic couplings
Direct back scattering under control
Requirement
OMC has
Require second in-vacuum Faraday
OPO ring topology is very helpful
Motion of scatterer
Backscatter reflectivity

16. Noise Model Highlights
Phase noise requirement < 50 mrad rms
Squeeze angle deviation
Remaining RF sidebands transmitted through OMC are important
Detected quadrature
Anti-squeeze projection
PCR is the total carrier after OMC  10 mW for ELIGO
PCD is carrier due to contrast defect  0.4 mW (rest is from length offset)
The total amplitude of the phase modulation is related to the total power in the RF sidebands and the amount of carrier power that is the same phase as the contrast defect.
Total rms phase fluctuations are sqrt[TSB*PSB*PCD/PCR^2]
Phase Noise (°)
Squeeze angle deviation
PCR/PCD

17. Noise Model Highlights
Other noise couplings
Laser frequency noise not important due to large servo bandwidth (500 kHz)
Path length variations not important due to large servo bandwidth (few kHz)
Shot noise: 1 mW per detector should be enough
OPO length fluctuations are not suppressed by Local Oscillator (LO) servo

18. ANU Traveling Wave OPO 150 mm 200 mm PZT Actuator Squeezing Out
Oven/
Temperature
Sensor
Crystal
Squeezing
Out
Pump light In
PZT Actuator
150 mm
200 mm 18

19. ANU OPO Squeezing Performance
Electronics
Mains harmonics
Cross coupling from Coherent Lock
Quantum noise
Electronic Noise?
Lab environment
Acoustic Noise
6dB
Observed squeezing
8dB
Inferred squeezing
H1 Squeezer Status 19

20. Schedule and Planning Reviewed, approved and funded (08/2009)
ANU will continue on development of OPO
On track for Spring 2010 delivery
MIT will continue with SHG & laser locking
On track to begin integration with OPO in Spring 2010
Electronics production at LHO moving forward
RF, PDs, TTFFS and length servos (common mode board) to arrive at MIT December 2009
Planning for installation in Feb. 2011
Depends on Advanced LIGO commissioning sequence and S6

21. Highlights and summary
Outstanding team assembled
Graduate students Sheila Dwyer (MIT), Sheon Chua (ANU) and Michael Stefsky (ANU), Alexander Khalaidovski (AEI)
Led by Daniel Sigg at LHO
Impressive progress on OPO development at ANU
6 dB of squeezing observed
Traveling wave bowtie design works
Laser, optical table and clean room installed at MIT
AEI loaner SHG at MIT producing green
Entering optimization phase
In the process of building our own (copy of AEI design)
Noise model and simulation done
Electronics design done for RF distribution
Shared with advanced LIGO

22. The End GW Detector Laser Faraday isolator Homodyne Detector GW Signal
SHG
Faraday isolator
OPO
Homodyne Detector
Squeeze
Source
GW Signal