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Displacement noise free interferometoryfor gravitational wave detection

National Astronomical Observatory of Japan,Ochanomizu UniversityA,

LIGO project, California Institute of TechnologyB

Kyoto UniversityC,Max-Planck-Institut für GravitationsphysikD

Shuichi Sato, Keiko KokeyamaA, Seiji Kawamura, Robert L.WardB,Atsushi NishizawaC, Yanbei ChenD, Archana PaiD and Kentaro SomiyaD

Introduction

Displacement noise

Fundamental noises: Seismic, thermal, radiation pressure, etc…

Practical/technical noises: alignment noise, electronics noise, etc…

If, the displacement noise has gone…

Shot-noise-limited interferometer in all frequency band

If, it is shot-noise-limited interferometer…

The sensitivity goes better with laser power

However…

Currently suggested DFI does not apply, for audio frequency band

Sensitivity

Frequency

Cancellation ofDisplacement noise

Better shot noise level

11-15 September 2007@Sendai Civic Auditorium11-15 September 2007@Sendai Civic AuditoriumTAUP2007 (Sendai) TAUP2007 (Sendai)

History

ReferenceKawamura and Chen, PRL 93 (2004) 211103Chen and Kawamura, PRL 96 (2006) 231102Chen, Pai, Somiya, Kawamura, Sato, Kokeyama and Ward,

PRL 97 (2006) 151103, (gr-qc/0603054)Sato, Kawamura, Kokeyama, Ward, Chen, Pai and Somiya,

PRL 98 (2007) 141101, (gr-qc/0608095)

11-15 September 2007@Sendai Civic Auditorium11-15 September 2007@Sendai Civic AuditoriumTAUP2007 (Sendai) TAUP2007 (Sendai)

History

ReferenceKawamura and Chen, PRL 93 (2004) 211103Chen and Kawamura, PRL 96 (2006) 231102Chen, Pai, Somiya, Kawamura, Sato, Kokeyama and Ward,

PRL 97 (2006) 151103, (gr-qc/0603054)Sato, Kawamura, Kokeyama, Ward, Chen, Pai and Somiya,

PRL 98 (2007) 141101, (gr-qc/0608095)

11-15 September 2007@Sendai Civic Auditorium11-15 September 2007@Sendai Civic AuditoriumTAUP2007 (Sendai) TAUP2007 (Sendai)

Principle of DFIGWs

DisplacementDisplacement

Point1: Difference of effects, GWs v.s. Displacement

GWs: accumulated phase shift on the whole path

Displacement: instantaneous

Point2: Multiple interferometer network

Share the displacement information

Manipulation of the signals

Cancel the displacement information

Remaining GWs signals

DFI: different approach

Suppression v.s. Cancellation

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DFI configuration

3-dimensional Mach-Zehnder interferometer

Light travels on the rigdeline

2-sets of bi-directional Mach-Zehnder interferometers

2-Beam Splitters at the tops

4-Folding mirrors at the side apexes

One of DFI configuration (most simple)

Still looking for other configuration

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DFI features

3-dimensional Mach-Zehnder interferometer

Combination of 4-interferometer’s output

Complete cancellation of optic’s displacements

Remaining GW signals

Effective frequency fc ~100MHz for L=1mChen et.al, PRL 97 (2006) 151103

11-15 September 2007@Sendai Civic Auditorium11-15 September 2007@Sendai Civic AuditoriumTAUP2007 (Sendai) TAUP2007 (Sendai)

DFI features

3-dimensional Mach-Zehnder interferometer

Combination of 4-interferometer’s output

Complete cancellation of optic’s displacements

Remaining GW signals

Effective frequency fc ~100MHz for L=1mChen et.al, PRL 97 (2006) 151103

11-15 September 2007@Sendai Civic Auditorium11-15 September 2007@Sendai Civic AuditoriumTAUP2007 (Sendai) TAUP2007 (Sendai)

Experiment (1) -Optical layout-

Proof-of-principle experiment

To confirm

Cancellation of FM displacement

Cancellation of BS displacement

Finite sensitivity to GWs signals

Partial demonstration

Using one set of bi-directional Mach-Zehnder interferometer

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Experiment (2) -Setup-

（前回の学会で報告）For GWs

For displacementnoise of FM

2-D bi-directional MZI

Sharing optical paths

Transfer function measurement

From D/GWs simulator to DFI

D/GWs simulation

FM: EOM at the center of the path

GWs: EOM at the asymmetric position -> makes “GWs-like” signal

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Experiment (3) -Cancellation of FM displacement-

180

90

0

-90

-180

Phase [degree]

105

106

107

108

Frequency [Hz]

-110

-100

-90

-80

-70

-60

-50

Amplitude [dB]

MAX50dBMZI2 output

MZI1 output

DFI outputtuned@25MHz

DFI output

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Experiment (4) -Sensitivity to GWs-

-110

-100

-90

-80

-70

-60

Amplitude [dB]

105

106

107

108

Frequency [Hz]

180

90

0

-90

-180

Phase [degree]

GWs: remaining around fc

MZI2 output

MZI1 output

DFI output

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First DFI using conventional interferometory

DFI feature was confirmed

FM cancellation

(BS cancellation: in separate experiment)

Sensitive to GWs

Next:

Spectrum (sensitivity) measurement of DFI: ongoing

3-D complete DFI: just started

Invention of new configuration for practical application

Summary and next

11-15 September 2007@Sendai Civic Auditorium11-15 September 2007@Sendai Civic AuditoriumTAUP2007 (Sendai) TAUP2007 (Sendai)