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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
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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)
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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)
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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)
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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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QuickTime˛ Ç∆GIF êLí£ÉvÉçÉOÉâÉÄ
ǙDZÇÃÉsÉNÉ`ÉÉÇ å©ÇÈÇΩÇflÇ…ÇÕïKóvÇ≈Ç∑ÅB
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
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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
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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
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