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Test mass dynamics with optical springs proposed experiments at Gingin

Test mass dynamics with optical springs proposed experiments at Gingin. Chunnong Zhao (University of Western Australia) Thanks to ACIGA members Stefan Danilishin and Farid Khalili (Moscow State University) Yanbei Chen (Caltech). Contents: Gingin high optical power research facility

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Test mass dynamics with optical springs proposed experiments at Gingin

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  1. Test mass dynamics with optical springsproposed experiments at Gingin Chunnong Zhao (University of Western Australia) Thanks to ACIGA members Stefan Danilishin and Farid Khalili (Moscow State University) Yanbei Chen (Caltech) GWADW2010, May 19, 2010

  2. Contents: • Gingin high optical power research facility • 3-mode optomechanical transducer • Test mass dynamics with double optical springs • (negative optical inertia) • Summary GWADW2010, May 19, 2010

  3. Gingin high optical power test facility High optical power is necessary for improving advanced detector sensitivity, but it also introduces thermal lensingand various instabilities. GWADW2010, May 19, 2010

  4. Gingin high optical power test facility • On this facility, we have demonstrated: • Thermal lesing and thermal compensation • In-situ real time thermal lensing monitoring using Hartmann sensor • 3-mode opto-acoustic interactions • Cavity locking using ultra-low frequency vibration isolators • Current main focus: parametric instability and its control GWADW2010, May 19, 2010

  5. N Future 80m interferometer East-end Station East Fabry-Perot Cavity M3 Mode Cleaner Power Recycling Cavity South-end Station Beam Splitter M1 M2 Nd:YAGlaser l = 1064nm South Fabry-Perot Cavity Signal Recycling Mirror To Detector Bench GWADW2010, May 19, 2010

  6. Currently, 2 independent 80m cavities South arm: Sapphire test masses with LIGO SOS suspension Finesse, ~1300, 10 W laser Tested thermal lensing and thermal compensation; Observed 3-mode opto-acoustic interactions; Study 3-mode optomechanical transducer. East arm: Fused silica test masses with UWA isolators and suspensions Nominal cavity finesse, 15000 50W laser to be installed in August Main goals are test the parametric instability and its control. GWADW2010, May 19, 2010

  7. 3-mode optomechanical transducer Input light frequency wo Scattering into TEMmn, frequency w1 Test mass internal mode wm Cavity Fundamental mode (TEM00, frequency wo) frequency matching and spatial overlap of acoustic and optical modes GWADW2010, May 19, 2010

  8. DwTEM FSR 1 2 3 4 5 3-mode optomechanical transducer 0 w DwTEM w0 w0 +wm GWADW2010, May 19, 2010

  9. CO2 laser thermal tuning the radius of curvature He-Ne laser CO2 laser Probe beam (800nm) Vacuum tank Nd:YAG laser Vacuum pipe Sapphire test mass Hartmann sensor GWADW2010, May 19, 2010

  10. CCD Fundamental mode Laser High order mode ITM ETM CP QPD x y Spectrum Analyzer 3-mode optomechanical transducer CO2 Laser GWADW2010, May 19, 2010

  11. 3-mode optomechanical transducer Test mass thermal noise at ~181.6 kHz GWADW2010, May 19, 2010

  12. 3-mode optomechanical transducer potential to observe the quantum radiation pressure noise The vibration of silicon nitride membrane excites high transverse optical mode QPD Laser 1mm x 1mm x 50nm Finesse=10,000 Meff=40 ng, T=4 k, wm=2p*200 kHz Qm=106 Circulating power= 0.5W Radiation pressure noise ~ thermal noise @ mechanical resonance GWADW2010, May 19, 2010

  13. Test mass dynamics with optical springs Motivation: The SQL in terms of GW strain sensitivity: A system with larger mechanical susceptibility (/m) has smaller SQL than the free mass SQL Y. Chen, et al, LIGO-T1000069-v1 GWADW2010, May 19, 2010

  14. Test mass dynamics with optical springs Considering the test mass dynamics with double optical springs (DOS) , • Here, s=-i; F is the force applied on the test mass, x is the displacement , GWADW2010, May 19, 2010

  15. Test mass dynamics with optical springs This is achievable at Gingin with a 3-mirror cavity: Driving force PM: power recycling mirror; PBS: polarization beam splitter; BS: beam splitter; PD: photodetector; ITM: input test mass; ETM: end test mass. The same configuration can also be used to demonstrate the local readout (optical bar) GWADW2010, May 19, 2010

  16. Test mass dynamics with optical springs Test mass, m=0.8 kg, cavity length L=80m, cavity circulating power: I1= 3kW, I2=10kW, Cavity detuning: 1/2=200 Hz 2/2=-500 Hz Cavity linewidth: 1/2 =36 Hz; 2/2 =400 Hz; Free mass With DOS GWADW2010, May 19, 2010

  17. Summary • Gingin high optical power research facility consists: • High power lasers • Advanced vibration isolators and test mass suspension • High finesse cavities • In addition to the parametric instability research, we propose to study: • High sensitivity optomechanical transducer (potential for detecting the quantum radiation pressure noise) • Optical negative inertia • Local readout (optical bar) GWADW2010, May 19, 2010

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