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Kazuhiro Yamamoto Henning Kaufer, Tobias Westphal, Daniel Friedrich, Helge Mueller-Ebhardt,

Radiation Pressure Noise Experiment in Hannover. Kazuhiro Yamamoto Henning Kaufer, Tobias Westphal, Daniel Friedrich, Helge Mueller-Ebhardt, Stefan Gossler, Karsten Danzmann and Roman Schnabel Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut)

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Kazuhiro Yamamoto Henning Kaufer, Tobias Westphal, Daniel Friedrich, Helge Mueller-Ebhardt,

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  1. Radiation Pressure Noise Experiment in Hannover Kazuhiro Yamamoto Henning Kaufer, Tobias Westphal, Daniel Friedrich, Helge Mueller-Ebhardt, Stefan Gossler, Karsten Danzmann and Roman Schnabel Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut) Institut fuer Gravitationsphysik, Leibniz Universitaet Hannover Kentaro Somiya Waseda University Farid Y. Khalili, Stefan L. Danilishin Moscow State University 19 May 2010 Gravitational-Wave Advanced Detector Workshop @Hearton Hotel Kyoto, Kyoto, Japan

  2. 0.Abstract Radiation pressure noise measurement with extremely light but translucent mechanical oscillator New topology : Michelson-Sagnac interferometer Theoretical outlines Current status of experiment Future work

  3. Related talks CLIO-MQM (Cryogenic Laser Interferometer Observatory-Macroscopic Quantum Measurement) Workshop 24th and 25th May Waseda Institute for Advanced Study, Tokyo, Japan S.L. Danilishin, “Towards mechanical non-Gaussian states with optical interferometers” F.Y. Khalili, “Up-converter regime in the membrane experiments” K. Yamamoto, “Nano-gram membrane experiment at AEI”

  4. Contents • Introduction • Current status • Future work • Summary

  5. 1.Introduction Interferometric gravitational wave detector Current : First generation (LIGO,VIRGO,GEO,TAMA,CLIO) Future : Second generation (GEO-HF, Advanced LIGOand VIRGO, LCGT, AIGO) Third generation (Einstein Telescope) Quantum noise : Limit of future interferometer Shot noise : Phase fluctuation Radiation pressure noise : Amplitude fluctuation

  6. 1. Introduction Radiation pressure noise (1) Photons come at random (amplitude fluctuation). Back action of photon is also at random. → Radiation pressure noise http://spacefiles.blogspot.com

  7. 1. Introduction Standard Quantum Limit Standard Quantum Limit (SQL) is a fundamental limit for naively optimized conventional interferometers. Nobody observed radiation pressure noise ! shot noise ~ P-1/2 Large radiation pressure noise quantum noise with 100x increased laserpower ~ m1/2 quantum radiation pressure noise standard quantum limit ~ P1/2 High laser power Light mass

  8. 1. Introduction Membrane (Si3N4 in frame) Mechanical properties frame: 7,52 mm2 x 200 µm Area: 1,5 mm x 1,5 mm Thickness: 75 nm Effective mass: ~100 ng Resonant frequency: ~73 kHz Optical properties Power Reflectance: ~ 33% Absorption: ≤ 150 ppm Flatness: 1 nm? Micro roughness: 0,2 nm? Scattering: → 0 J.D. Thompson et al., Nature 452 (2008) 72-76.

  9. 1. IntroductionMichelson-Sagnac interferometer(1) Steering mirror Membrane From laser source Steering mirror Beam splitter

  10. 1. IntroductionMichelson-Sagnac interferometer(2) Sagnac mode Symmetric port Anti symmetric port (no light of Sagnac mode) Michelson mode Membrane position is adjusted to keep this port dark.

  11. 1. IntroductionMichelson-Sagnac interferometer(3) Steering mirror Membrane Power recycling mirror Laser source Steering mirror Beam splitter Signal recycling mirror Recycling techniques are useful even if the membranereflectance is low.

  12. 1. Introduction Goal sensitivity Temperature: 1K Q: 107 Effective Mass: 125ng Resonance: 75kHz Power at BS: 1 W Signal recycling mirror 99.8 % amplitude reflectance Radiation pressure noise is 2 and 3 times larger than shot noise and thermal noise. K. Yamamoto et al., Physical Review A 81 (2010) 033849.

  13. 1. Introduction Node of Sagnac mode Sagnac mode : Clockwise and counterclockwise beams There is interference between them. Standing wave Nodes and anti nodes Anti symmetric port is dark. Membrane must be on node or anti-node. We prefer membrane on node because of absorption.

  14. 2. Current status Membrane (Si3N4 in frame) Mechanical properties frame: 7.52 mm2 x 200 µm Area: 1.5 mm x 1.5 mm Thickness: 75 nm Effective mass: ~ 100 ng Resonant frequency: ~ 73 kHz Q: ~ 1.3x106 Optical properties Power reflectance: ~ 33% Absorption: ≤ 150 ppm Flatness: 1 nm? Micro roughness: 0,2 nm? Scattering: → 0 about 1 mm J.D. Thompson et al., Nature 452 (2008) 72-76.

  15. 2. Current status Membrane (Si3N4 in frame) Heat absorption in membrane (in Michelson-Sagnac interferometer) Node of Sagnac mode (small absorption) First mode Anti node (large absorption) Fitting : Second polynomial (Physical mechanism is not clear yet)

  16. 2. Current status Membrane (Si3N4 in frame) Heat absorption in membrane Second mode

  17. 2. Current status Membrane (Si3N4 in frame) Heat absorption in membrane Fourth mode Temperature gradient

  18. 2. Current status Michelson-Sagnac interferometer Mode cleaner Nd:YAG laser EOM Photo detector Without power and signal recycling Vacuum tank (10-6 mbar) Photo detector (signal of membrane motion) Membrane

  19. 2. Current status Inside vacuum tank From laser source Steering mirror Anti symmetic port Membrane holder Beam splitter Steering mirror

  20. 2. Current status Measured power spectrum Off resonance : Intensity noise On resonance : Thermal noise 5*10-16m/rtHz

  21. 2. Current status Standard Quantum Limit on resonance JILA/NIST group claims that their sensitivity is below Standard Quantum Limit (SQL). 4.8*10-15m/rtHz J.D. Teufel et al., Nature Nanotechnology 4 (2009) 820.

  22. 2. Current status Standard Quantum Limit on resonance Max-Planck-Institut (MPI) fuer Quantenoptik group also claims that their sensitivity is below Standard Quantum Limit (SQL). 5.7*10-16m/rtHz SQL Recent result from same group (arXiv:1003.3752) G. Anetsberger et al., Nature Physics 5 (2009) 909.

  23. 2. Current status Standard Quantum Limit on resonance What is their definition of Standard Quantum Limit (SQL) ? Standard Quantum Limit (SQL) depends on (only) mechanical susceptibility. Standard Quantum Limit (SQL) of NIST and MPI fuer Quantenoptik is constant around the resonance.

  24. 2. Current status Standard Quantum Limit on resonance What is their difinition of Standard Quantum Limit (SQL) ? Standard Quantum Limit (SQL) depends on (only) mechanical susceptibility. They compare off resonance sensitivity with Standard Quantum Limit (SQL) on resonance !

  25. 2. Current status Standard Quantum Limit on resonance Our sensitivity is also below Standard Quantum Limit (SQL) and better or comparable! 5*10-16m/rtHz

  26. 3. Future work • Reduction of noise (to observe off resonance thermal noise) Laser intensity stabilization (in progress) (2) Signal recycling (3) Cryogenic apparatus (about 1K : 3He evacuation) Suspension

  27. 4. Summary Radiation pressure noise measurement with extremely light but translucent membrane New topology : Michelson-Sagnac interferometer Goal sensitivity, Nodes of Sagnac mode Current status of experiment Incident power dependence of resonant frequency Operation without power and signal recycling Current sensitivity (5*10-16 m/rtHz) Off resonance sensitivity below Standard Quantum Limit (SQL) on resonance Future work Laser intensity stabilization, Cryogenic apparatus and so on

  28. Vielen Dank für die Aufmerksamkeit (Thank you for your attention)

  29. 1. Introduction Radiation pressure noise Advanced LIGO Radiation pressure noise Sensitivity (/rtHz) Mirror thermal noise Vacuum Frequency(Hz)

  30. 1. Introduction Sizes of oscillators kg Effective Mass Hz pg Resonant frequency T.J. Kippenberg and K. J. Vahala, Science 321 (2008) 1172 MHz 30

  31. 1. Introduction Membrane (Si3N4 in frame) Mechanical properties frame: 7,52 mm2 x 200 µm Area: 1,5 mm x 1,5 mm Thickness: 75 nm Effective mass: ~100 ng Resonant frequency: ~73 kHz J.D. Thompson et al., Nature 452 (2008) 72-76.

  32. 1. Introduction compare different approaches 1 N. Mavalvala, Elba conference (2008) 2 C.M. Mow-Lowry et al., Journal of Physics:Congerence Series 32 362-367 (2006) 3 T. Corbitt, Elba conference (2008) 4 J.D. Thompson et al., Nature 452 72-76 (2008)

  33. 2. Theoretical outlines I will explain Two differences from simple Michelson (1)Radiation pressure noise on membrane (2)Node of Sagnac mode and goal sensitivity of our interferometer.

  34. 2. Theoretical outlines Radiation pressure noise on membrane Interference Interference Membrane Conclusion : Radiation pressure noise is proportional to power reflectance of membrane even if the membrane is at node of Sagnac mode.

  35. 2. Current status Optical table Vacuum tank Periscope Mode cleaner Laser source

  36. 2. Current status Membrane holder Stage PZT with hole Membrane Membrane frame

  37. 3. Current status Michelson-Sagnac interferometer Steering mirror Membrane holder Steering mirror From laser source Beam splitter

  38. 2. Theoretical outlines Standart Quantum Limit (SQL) SQL of Michelson-Sagnac interferometer (one membrane) SQL of Fabry-Perot Michelson interferometer (four mirrors) SQL of simple Michelson interferometer (two mirrors) H : Mechanical responce of one oscillator Our conjucture : SQL depends on number of mirrors (n).

  39. 3. Current status Calibration Measured fringe Fitting value Measured results agree with fitting. Photo detector output power [a.u.] Quater of wavelength Membrane displacement [nm] Calibration (photo detector output vs. displacement of membrane) is possible as like simpleMichelson interferometer.

  40. 3. Current status Resonant frequencies of membrane Fundamental mode (73kHz) Amplitude (dB) Frequency (kHz)

  41. 3. Current status Resonant frequencies of membrane Difference between theory and measurement (~1%) Difference between theory and measurement [kHz] Frequency [kHz]

  42. 75 nm 1,5 mm 3. Current status Q-values of membrane • Residual gas damping • → Vacuum (~ 10-6 mbar) Measurement Theory • Recoil loss • → Estimation: Q > 107 200 µm 75 nm Q • Thermoelastic damping • → Estimation: Q ~ 5 x 107 • Bulk loss • → Unknown 10-6 Pressure [mbar] • Loss on surface • → Unknown Time [sec] • Our measurement: Q ~ 1.3 x106 @ 300 K • Measurement of other group: Q ~ 1 x107 @ 0.3 K • B.M. Zwickl et al., Applied Physics Letters 92(2008)103125.

  43. 3. Current status Reflectance of membrane Membrane as etalon Power reflectivity S-polarized P-polarized Incident angle [degree]

  44. vacuum system to reach < 10-6 mbar actual pressure in experiment: 1.5·10-7 mbar backing pump pressure: 10-1 mbar, not good enough to use ducted vacuum

  45. Q-measurement actual status of the table laser preparation membrane periscopes

  46. recoil loss energy transfer to membraneholder limits Q • many unknown values • had no verification for Harris results • → designed very sturdy mount • recent results: • it should be sufficient to conserve Q of the small frame to be not limited!!! • we will design a smaller mount for • further experiment

  47. Q-measurement actual readout scheme ringdown time: • 106 periods per ringdowntime! • → use lock in amplifier • (variable filters) • our lock-in amp. is too slow! • → mixer shifts signal to some kHz

  48. Q-measurement actual readout scheme 106 periods per ringdowntime! → mix signal down (shift to lower freq.) Lock-in amp. is too slow! → second mixer for some kHz

  49. nonlinearity of the oscillation comparison of our results to Harris` Harris et al. APL 92, (2008) our results

  50. locking scheme for PR-cavity using Pound Drever Hall signal • michelson acts as mirror • membrane-position • dependent reflectivity • (and phase)

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