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Demonstration of lock acquisition and optical response on Detuned RSE interferometer

Demonstration of lock acquisition and optical response on Detuned RSE interferometer at Caltech 40m GWADW-VESF meeting @ Elba May 31, 2006 Osamu Miyakawa, Caltech + 40m team. Advanced LIGO optical configuration. LIGO:Power recycled FPMI

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Demonstration of lock acquisition and optical response on Detuned RSE interferometer

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  1. Demonstration of lock acquisition and optical response on Detuned RSE interferometer at Caltech 40m GWADW-VESF meeting @ Elba May 31, 2006 Osamu Miyakawa, Caltech + 40m team GWAWD-VESF meeting at Elba, May 2006

  2. Advanced LIGO optical configuration • LIGO:Power recycled FPMI • Optical noise is limited by Standard Quantum Limit (SQL) • AdvLIGO:GW signal enhancement using Detuned RSE • Two dips by optical spring, optical resonance • Can overcome the SQL　　QND detector FP cavity Power PRM Laser FP cavity BS GW signal Detuning SRM GWAWD-VESF meeting at Elba, May 2006

  3. Historical review of Advanced interferometer configuration ~1986 Signal Recycling (Dual Recycling) [B.Meers] ~1998 Garching 30m [G.Heinzel] GEO600 Glassgow 10m ~2000 Tabletop with new control • Caltech(RSE)[J.Mason] • Florida(DR) • Australia(RSE)[D.Shaddock] ~1993 RSE • Idea [J.Mizuno] • Tabletop [G.Heinzel] ~2005 Caltech 40m • Suspended mass • DRSE+PR ~2013 AdLIGO(DRSE) LCGT(BRSE) AdVIRGO ~2002 NAOJ 4m Susp. mass BRSE(No PR) [O.Miyakawa] ~2004 NAOJ 4m Susp. mass DRSE(No PR) [K.Somiya] ~2001 QND study[Y.Chen, A. Buonanno] • Optical spring • Readout scheme GWAWD-VESF meeting at Elba, May 2006

  4. BS SRM PRM Bright port Dark port X arm Y arm Caltech 40 meter prototype interferometer An interferometer as close as possible to the Advanced LIGO optical configuration and control system • Detuned Resonant Sideband Extraction(DRSE) • Power Recycling • Suspended mass • Digital controls system • To verify optical spring and optical resonance • To develop DC readout scheme • To extrapolate to AdLIGO via simulation GWAWD-VESF meeting at Elba, May 2006

  5. Carrier (Resonant on arms) -f2 -f1 f1 f2 Signal extraction scheme ETMy • Mach-Zehnder is installed to eliminate sidebands of sidebands. • Only + f2is resonant on SRC. • Unbalanced sidebands of +/-f2 due to detuned SRC produce good error signal for Central part. • Arm cavity signals are extracted from beat between carrier and f1 or f2. • Central part (Michelson, PRC, SRC) signals are extracted from beat between f1 and f2, not including arm cavity information. 4km f2 ITMy ETMx PRM ITMx BS 4km f1 SRM Single demodulation Arm information Double demodulation Central part information GWAWD-VESF meeting at Elba, May 2006

  6. PMC trans Locked by internal modulation f2 PZT f1 f2 Carrier Carrier EOM2 f1 EOM1 EOM2 To MC f2=166MHz -f2 -f1 f1=33MHz f2 -f1 f1 -f2 133MHz 199MHz EOM1 PD Mach-Zehnder interferometerto eliminate sidebands of sidebands Mach-Zehnder interferometer with no sidebands of sidebands Series EOMs with sidebands of sidebands PMC transmitted to MC GWAWD-VESF meeting at Elba, May 2006

  7. Pre-Stabilized Laser(PSL)and 13m Mode Cleaner(MC) BS East Arm • 10W MOPA126 • Frequency Stabilization Servo (FSS) • Pre-Mode Cleaner (PMC) • Intensity Stabilization Servo(ISS) • 13m suspended-mass Mode Cleaner ITMx ETMx ITMy PSL MOPA126 FSS PMC MZ ISS 40m Y-arm cavity South Arm Mode Cleaner 13m MC Squeezer Detection bench ETMy GWAWD-VESF meeting at Elba, May 2006

  8. Each optic has five OSEMs (magnet and coil assemblies), four on the back, one on the side The magnet occludes light from the LED, giving position Current through the coil creates a magnetic field, allowing mirror control LIGO-I type single suspension GWAWD-VESF meeting at Elba, May 2006

  9. Carrier 33MHz 166MHz The way to full RSE Detuned dual recycled Michelson RSE 5 DOF lock with offset in CARM ETMy Reducing CARM offset ITMy PRM ETMx ITMx BS SRM GWAWD-VESF meeting at Elba, May 2006

  10. Lock acquisition procedure towards detuned RSE Low gain High gain TrY PDs POY ITMy 166MHz POX ITMx 13m MC BS High gain 33MHz PRM TrX PDs Low gain PO DDM SP33 SRM SP166 SP DDM AP166 AP DDM GWAWD-VESF meeting at Elba, May 2006

  11. Normalization process OSA@SP DRMI + 2arms with offset using digitally normalized Carrier Resonant Lock Off-resonant Lock point Unbalanced 166MHz • Avoids coupling of carrier in PRC • Lock with low bandwidth control • High cavity pole 33MHz Belongs to next carrier Belongs to next carrier OSA@AP 1/sqrt(TrX) 1/sqrt(TrY) Belongs to next carrier Lock acquisition procedure towards detuned RSE Low gain High gain DRMI TrY PDs POY ITMy 166MHz POX ITMx 13m MC BS High gain 33MHz PRM TrX PDs Low gain PO DDM SP33 SRM SP166 I SP DDM Q AP166 AP DDM GWAWD-VESF meeting at Elba, May 2006

  12. Normalization process DRMI + 2arms with offset using digitally normalized Resonant Lock Off-resonant Lock point Ly=38.55m Finesse=1235 • Avoids coupling of carrier in PRC • Lock with low bandwidth control • High cavity pole 1/sqrt(TrX) 1/sqrt(TrY) Lx =38.55m Finesse=1235 T=7% T=7% Lock acquisition procedure towards detuned RSE Low gain High gain TrY PDs POY ITMy 166MHz POX ITMx 13m MC BS High gain 33MHz PRM TrX PDs Low gain PO DDM SRM SP166 SP33 I SP DDM Q AP166 AP DDM GWAWD-VESF meeting at Elba, May 2006

  13. Design RSE peak ~ 4kHz + -1 + Ly=38.55m Finesse=1235 Lx =38.55m Finesse=1235 T=7% T=7% Lock acquisition procedure towards detuned RSE Normalization process Short DOFs -> DDM CARM-> Normalized RF DARM->Normalized RF CARM with offset DARM with no offset Low gain High gain TrY PDs POX/TrX+POY/TrY CARM + + POY DARM ITMy 166MHz POX ITMx 13m MC High gain BS 33MHz PRM TrX PDs Low gain PO DDM SRM SP33 SP166 SP DDM AP166 AP DDM AP166/(TrX+TrY) GWAWD-VESF meeting at Elba, May 2006

  14. + -1 + Ly=38.55m Finesse=1235 GPR=14.5 Lx =38.55m Finesse=1235 T=7% T=7% Lock acquisition procedure towards detuned RSE Normalization process Low gain High gain TrY PDs Reduce CARM offset to Full RSE POX/TrX+POY/TrY CARM + + DARM ITMy 166MHz POX ITMx ITMx 13m MC High gain BS 33MHz PRM TrX PDs Low gain PO DDM SRM SP33 SP166 SP DDM AP166 AP DDM AP166/(TrX+TrY) GWAWD-VESF meeting at Elba, May 2006

  15. Optical Spring stiffness ~107 N/m BMW Z4 ~ 104 N/m DARM Optical response with fit to A.Buonanno & Y.Chen formula Optical spring and optical resonance of detuned RSE were measured and fitted to ABYC formula. Radiation pressure:F = 2 P / c Detuned Cavity -> dF/dx Description of data, fit: http://arxiv.org/abs/gr-qc/0604078 GWAWD-VESF meeting at Elba, May 2006

  16. h arm cavity h Beam splitter arm cavity laser Signal recycling mirror b a Standard Quantum Limit Mathematical description foroptical spring in detuned RSE ABYC equation:relation using two photon mode among input vacuum a , output field b, input power and gravitational wave h a :input vacuum b :output field M2: C11C22-C12C21 h :gravitational wave hSQL:standard quantum limit t: transmissivity of SRM k: input power coupling b: GW sideband phase shift in IFO Strain sensitivity: ratio h and a on b Optical noise: ratio between a and b Measurement of optical response: ratio h and b a<<h; non-quantum measurement GWAWD-VESF meeting at Elba, May 2006

  17. Simple picture of optical spring in detuned RSE Let’s move arm differentially, X arm longer, Y arm shorter from full RSE Wrong SRM position Correct SRM position BRSE X arm Y arm Y arm X arm Power(W) Power(W) Power(W) DARM (Lx-Ly) DARM (Lx-Ly) DARM (Lx-Ly) • Power X arm down, Y arm up X arm down, Y arm down X arm up, Y arm down • Radiation pressure X arm down, Y arm up X arm down, Y arm down X arm up, Y arm down • Spring constant Positive (optical spring) N/A Negative (no optical spring) GWAWD-VESF meeting at Elba, May 2006

  18. Frequency sweep of optical spring ~1900W ~270W GWAWD-VESF meeting at Elba, May 2006

  19. CARM optical resonanceand Dynamic compensative filter Optical gain of CARM Open loop TF of CARM Optical gain (normalized by transmitted power) shows moving peaks due to reducing CARM offset. We have a dynamic compensative filter having an exactly the same shape as optical gain except for upside down. Open loop transfer function has no phase delay in all CARM offset. GWAWD-VESF meeting at Elba, May 2006

  20. CARM optical springs Solid lines are from TCST Stars are 40m data Max Arm Power is ~80 GWAWD-VESF meeting at Elba, May 2006

  21. fringe offset β Loss mismatch GW readout, Systems • DC rather than RF for GW sensing • Requires Output Mode-Cleaner to reject RF • Offset ~ 1 picometer from dark fringe can tune from 0 to 80 deg with 0-100 mW of fringe offset power Mode matching telescope OMC DC PD GWAWD-VESF meeting at Elba, May 2006

  22. SHG 2W from MOPA Squeezed vacuum to IFO OPO Squeezing Tests at the 40m • Go from MIT group brought an audio frequency squeezer to 40m, and injection of squeezed vacuum will be tested. • SHG, OPO ready, homodyne detector being developed. • Time to take steps toward injection to 40m interferometer • DRSE configuration will be tested • LIGO-like control systems for eventually porting squeezing technology to long baseline ifos GWAWD-VESF meeting at Elba, May 2006

  23. Other ideas • Low frequency-low frequency RF modulation scheme (40m:33-55MHz, AdLIGO:27-45MHz) instead of LF-HF RF • Alignment Sensing and Control (ASC) on detuned RSE with LF-LF RF modulation • ASC with lighter mirrors in order to investigate pitch and yaw optical springs • Variable band operation using SRC error signal normalized by LF f2 power GWAWD-VESF meeting at Elba, May 2006

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