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11-15 September 2007@Sendai Civic Auditorium

Displacement noise free interferometory for gravitational wave detection. Shuichi Sato, Keiko Kokeyama A , Seiji Kawamura, Robert L.Ward B , Atsushi Nishizawa C , Yanbei Chen D , Archana Pai D and Kentaro Somiya D. National Astronomical Observatory of Japan, Ochanomizu University A ,

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11-15 September 2007@Sendai Civic Auditorium

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  1. Displacement noise free interferometory for gravitational wave detection Shuichi Sato, Keiko KokeyamaA, Seiji Kawamura, Robert L.WardB, Atsushi NishizawaC, Yanbei ChenD, Archana PaiD and Kentaro SomiyaD National Astronomical Observatory of Japan, Ochanomizu UniversityA, LIGO project, California Institute of TechnologyB Kyoto UniversityC, Max-Planck-Institut für GravitationsphysikD TAUP2007 (Sendai) 11-15 September 2007@Sendai Civic Auditorium

  2. Introduction Cancellation of Displacement noise • 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 Better shot noise level TAUP2007 (Sendai) 11-15 September 2007@Sendai Civic Auditorium

  3. History • Reference • Kawamura and Chen, PRL 93 (2004) 211103 • Chen and Kawamura, PRL 96 (2006) 231102 • Chen, 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) TAUP2007 (Sendai) 11-15 September 2007@Sendai Civic Auditorium

  4. History • Reference • Kawamura and Chen, PRL 93 (2004) 211103 • Chen and Kawamura, PRL 96 (2006) 231102 • Chen, 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) TAUP2007 (Sendai) 11-15 September 2007@Sendai Civic Auditorium

  5. Principle of DFI GWs • 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 Displacement Displacement TAUP2007 (Sendai) 11-15 September 2007@Sendai Civic Auditorium

  6. 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 TAUP2007 (Sendai) 11-15 September 2007@Sendai Civic Auditorium

  7. 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=1m Chen et.al, PRL 97 (2006) 151103 TAUP2007 (Sendai) 11-15 September 2007@Sendai Civic Auditorium

  8. 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=1m Chen et.al, PRL 97 (2006) 151103 TAUP2007 (Sendai) 11-15 September 2007@Sendai Civic Auditorium

  9. 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 TAUP2007 (Sendai) 11-15 September 2007@Sendai Civic Auditorium

  10. Experiment (2) -Setup- • 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 （前回の学会で報告） For GWs For displacement noise of FM TAUP2007 (Sendai) 11-15 September 2007@Sendai Civic Auditorium

  11. Experiment (3) -Cancellation of FM displacement- MZI1 output MAX50dB MZI2 output DFI output DFI output tuned@25MHz TAUP2007 (Sendai) 11-15 September 2007@Sendai Civic Auditorium

  12. Experiment (4) -Sensitivity to GWs- DFI output MZI1 output MZI2 output GWs: remaining around fc TAUP2007 (Sendai) 11-15 September 2007@Sendai Civic Auditorium

  13. Summary and next • 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 TAUP2007 (Sendai) 11-15 September 2007@Sendai Civic Auditorium

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