1. 11-15 September 2007@Sendai Civic Auditorium TAUP2007 (Sendai) Displacement noise free interferometory for gravitational wave detection National Astronomical Observatory of Japan, Ochanomizu University A, LIGO project, California Institute of Technology B Kyoto University C, Max-Planck-Institut für Gravitationsphysik D Shuichi Sato, Keiko Kokeyama A, Seiji Kawamura, Robert L.Ward B, Atsushi Nishizawa C, Yanbei Chen D, Archana Pai D and Kentaro Somiya D

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

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

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

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

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

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

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

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

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

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

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

13. 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 Auditorium TAUP2007 (Sendai)