1. Several Fun Research Projects at NAOJ for the Future GW Detectors
Picture: Sora Kawamura
Several Fun Research Projects at NAOJ for the Future GW Detectors
LIGO Caltech
Aug. 8, 2006
Seiji Kawamura
National Astronomical Observatory of Japan

2. National Astronomical Observatory of Japan (NAOJ)
NAOJ is located in Tokyo.
TAMA300 is located on the NAOJ campus.

3. Other research projects at NAOJ
Displacement-noise free Interferometer
RSE
DECIGO
MHz GW detection
QND

4. Displacement-noise free Interferometer

5. Motivation
Displacement noise: seismic Noise, thermal noise, radiation pressure noise
Cancel displacement noise  shot noise limited sensitivity
Increase laser power  sensitivity improved indefinitely
Diplacement noise
Displacement noise
Cancel displacement noise
Shot noise
Sensitivity
Increase laser power PD
Laser
Frequency

6. Principle 1: GW and mirror motion interact with light differently
On reflection
On propagation
Light
Mirror motion
Mirror motion
Difference outstanding for
GW wavelength  distance between masses

7. Principle 2: Mirror motion can be cancelled by combining interferometer outputs
Laser
Increase # of mirrors
Implement many interferometers
Take combination outputs  cancel mirror motion
Mirror motion PD
Laser PD
Mirror motion
Bi-directional MZ

8. Example of DFI Two 3-d bi-directional MZ Take combination of 4 outputs
Mirror motion completely cancelled
GW signal remains (f 2)

9. Experiment (Ideal) One bi-directional MZ GW Laser Mirror motion PD
Extract
GW 
Mirror motion

10. Experiment (Practical)
EOM used for GW and mirror motion
Simulated mirror motion Simulated GW
Mirror motion GW ～ ～
Laser
Laser PD PD
Ideal　　　　　　　　　　　　　　　　Practical

11. Results Mirror motion cancels out GW signal remains
Mirror motion to output
GW signal to output
Difference
Difference
Mirror motion　　　　　　　　GW signal

12. Next step
Implement cavity to reduce the effective frequency
Demonstrate the cancellation of the BS motion using two bi-directional MZ
References
Kawamura and Chen, PRL, 93, (2004)
Chen and Kawamura, PRL, 96 (2006)
Chen, Pai, Somiya, Kawamura, Sato, Kokeyama, Ward, submitted to PRL (gr-qc/ )
Sato, Kawamura, Kokeyama, Ward, Chen, Pai, and Somiya, to be submitted to PRL

13. RSE

14. 4m RSE
Supended mass RSE
Miniature suspension system

15. Previous Accomplishments
Tuned RSE (w/o PRM) locked
Detuned RSE (w/o PRM) locked
Optical spring effect observed
Miyakawa, Somiya, Heinzel, and Kawamura, Class. and Quantum Grav., 19 (2002) p
Somiya, Beyersdorf, Arai, Sato, Kawamura, Miyakawa, Kawazoe, Sakata, Sekido, Mio, Appl. Opt. 44 (2005) pp

16. Current Activity Try new signal extraction method Lock RSE (w/ PRM)
Backup for Advanced LIGO
Baseline for LCGT
Lock RSE (w/ PRM)

17. New Signal Extraction Method

18. Signal Matrix Baseline Design for LCGT Black: Analytic results
Red: Numerical simulation using “FINESSE” lp ls
diagonal ls
orthogonal
Baseline Design for LCGT lp

19. Delocation
Option for LCGT
- Could have potential advantages

20. Current Status MZ locked only w/ PM FP Michelson locked
Suspension system improved

21. DECIGO

22. What is DECIGO?
Deci-hertz Interferometer Gravitational Wave Observatory
- bridges the gap between LISA and terrestrial detectors.
- could attain high sensitivity because of lower confusion noise.
10-18
10-24
10-22
10-20
LISA
Terrestrial Detectors
Strain [Hz-1/2]
DECIGO
Confusion Noise
10-4
10-2
100
102
104
Frequency [Hz]

23. Pre-conceptual Design
FP-Michelson interferometer
Arm length: 1000 km
Laser power: 10 W
Laser wavelength: 532 nm
Mirror diameter: 1 m
Mirror mass: 100 kg
Finesse: 10
Orbit and constellation: TBD
Drag-free satellite
Arm cavity PD
Laser
Arm cavity
Kawamura, et al., CQG 23 (2006) S125-S131 PD
Drag-free satellite
Drag-free satellite

24. Drag-free and FP Cavity
Displacement Signal between S/C and Mirror
Local Sensor
Mirror
Thruster
Thruster
Actuator
Displacement signal between the two Mirrors

25. Requirements [Practical force noise] 4x10-17 N/Hz per mirror
[Frequency 1 Hz
First-stage stabilization： 1 Hz/Hz
Stabilization gain by common-mode arm length： 105
Common-mode rejection ratio： 105

26. Science by DECIGO BH+BH(1000Msun) @z=1 NS+NS@z=1 Correlation
for 3 years
NS-NS ( Msun)
z<1 (SN>26: 7200/yr)
z<3 (SN>12: 32000/yr)
z<5 (SN>9: 47000/yr)
IMBH ( Msun)
z<1 (SN>6000)

27. Acceleration of Expansion of the Universe
Expansion ＋Acceleration?
DECIGO GW
NS-NS (z～1)
Output
Template (No Acceleration)
Strain
Real Signal ?
Phase Delay～1sec (10 years)
Time
Seto, Kawamura, Nakamura, PRL 87, (2001)

28. Roadmap for DECIGO R&D Advanced R&D PF1 PF2 DECIGO
R&D
Advanced R&D
PF1
Design & Fabrication
Observation
PF2
Design & Fabrication
Observation
DECIGO

29. DECIGO Pathfinder1 Objectives Drag-free system Cavity locking in space
Modest sensitivity
at 0.1 – 1 Hz
Local Sensor
Actuator
Thruster

30. DECIGO Pathfinder2 Objectives DECIGO with modest specification
Cavity locking between two satellites
Meaningful sensitivity
Drag-free satellite
Arm cavity PD
Laser
Arm cavity PD
Drag-free satellite
Drag-free satellite

31. DECIGO Simulator Objectives Continual free-fall environment
Clamp release
Modest sensitivity down to 0.1Hz
Possibility of long arm
Clamp 2m
Vertical Position
1 sec
Release Hold
Release Hold
Release Hold
Time

32. DECIGO Demonstrator Air-hockey table Objectives Lock acquisition
Thruster
Thruster
Satellite A
Satellite B
Mirror A
Mirror B
Actuator
Local sensor
Local sensor
Air-hockey table
Objectives
Lock acquisition

33. Budget and Working Group
Will submit a budget request ($18M for 6 years) this fall
R&D for DECIGO
PF1
w/ Pulsar Timing
DECIGO-WG: 120 members currently

34. MHz GW detection

35. Objectives and Scope GW Sources at MHz
Detect GW at MHz
Develop technologies for synchronous recycling
GW Sources at MHz
Inspiral of mini black holes
GW from inflation period

36. Synchronous Recycling
Recycling Mirror
Laser BS
Drever, 1983
Dark Fringe
Photo detector

37. Response of Synchronous Recyclingx h t y y x GW l
Laser
GW  4 l BS
Photo detector
GW effect synchronously enhanced!

38. Plan for Table-top Experiment
Integration for 1 year
h  Hz-1/2
F  105
h  Hz-1/2
l  75 cm
fGW  100 MHz

39. Current Status Locked w/ low Finesse Noise Spectrum taken F  100 f 1
Non 50:50
Beam splitter
1 DOF to control
EOM
f 1
f GW - f 1 - BW
Output

40. First Noise Spectrum

41. QND

42. Objectives and Scope Plan
Beat SQL using ponderomotive squeezing
Use FP Michelson w/ super light mirrors
Plan
Observe radiation pressure noise
Reduce radiation pressure noise w/ homodyne detection
Beat SQL
Expand the effective frequency range

43. Ponderomotive Squeezing
Squeezed by phase change caused by reflection by free mass
Squeezing: frequency dependent
Cannot beat SQL w/ RF method
Laser
Noise
Signal
Vacuum
Caves, Walls & Milburn, Braginsky & Khalili, ...

44. Homodyne Detection
Local light
Laser
Homodyne phase
Signal
Noise
S/N can be improved by choosing appropriate homodyne phase!

45. Quantum Noise
Radiation pressure noise can be completely cancelled at one frequency
The frequency depends on homodyne phase

46. Strategy Use super-light mirror Use high finesse
Increase radiation pressure noise
Easier to detect
Use tuned IFO (no optical spring)

47. Design Parameter and Noise Estimate
Laser power
200 mW
Injected power into
the interferometer
120 mW
Finesse
7500
Front mirror mass
200 g
End mirror mass
23 mg
Diameter of the end mirror
3 mm
Thickness of the end mirror
1.5 mm
Beam radius on the end mirror
500 mm
Q factor of substrate
105
Loss angle of coating
4×10-4
Temperature
300 K
Length of the fiber
1 cm
Thickness of silica fiber
10 mm

48. Current Status Homodyne detection method verified Vacuum tank ready
Design of set-up complete
Fiber of 10 m drawn successfully

49. The End