Advanced LIGO optical configuration investigated in 40meter prototype LSC meeting at LLO

1. Advanced LIGO optical configuration investigated in 40meter prototype LSC meeting at LLO Mar. 22, 2005 O. Miyakawa, Caltech and the 40m collaboration LSC meeting at LLO, March 2005

2. Caltech 40 meter prototype interferometer Objectives • Develop lock acquisition procedure of detuned Resonant Sideband Extraction (RSE) interferometer, as close as possible to Advanced LIGO optical design BS • Characterize noise mechanisms • Verify optical spring and optical resonance effects • Develop DC readout scheme Next Rob’s talk • Extrapolate to AdLIGO via simulation • etc. SRM PRM Bright port Dark port X arm Y arm LSC meeting at LLO, March 2005

3. Important Milestones 2003 Installation of Four TMs and BS:done Lock of FP Michelson :done 2004 Installation of Power Recycling Mirror (PRM) ,Signal Recycling Mirror (SRM) :done Installation Mach-Zehnder to eliminate sideband of sideband :done DRMI locked with carrier resonance using dither for Michelson DOF. :done DRMI locked with sideband resonance using Double Demodulation(DDM) :done Off-resonant lock of signal arm cavity with DRMI :done Off-resonant lock of both arm cavities with DRMI :done Full carrier resonant of single arm with DRMI :done 2005 Full RSE :in progress Arm lock is really really difficult! LSC meeting at LLO, March 2005

4. Carrier Unbalanced 166MHz 33MHz Belongs to next carrier Belongs to next carrier DRMI lock withUnbalanced sideband by detuned cavity August 2004 • DRMI locked with carrier resonance (like GEO configuration) November 2004 • DRMI locked with sideband resonance (Carrier is anti resonant preparing for RSE.) Carrier 33MHz 166MHz ITMy ITMx BS PRM DDM PD DDM PD SRM OSA DDM PD Lock acquisitionAfter lock: MICH : dither @ 1200 Hz  DDM@AP PRC : 33MHz@SP  DDM@SP SRC : DDM@PO  DDM@PO Typical lock acquisition time : ~10sec Longest lock:2.5hour LSC meeting at LLO, March 2005

5. SP33,DDM,+/-33M,+/-166M@SP +/-33 off-resonant +/-33 resonant Abs +166resonant Design Lock point SP33 Lock point 0.56 degree (1.7nm) LSC meeting at LLO, March 2005

6. Double Demodulation at SP -0.4 350 0.4 0 0 dc=0 -0.1 -0.03 0.02 -0.3 0.2 -0.02 0.1 0.1 -0.3 0.03 0 l+ -0.04 0.2 0 0.3 -0.2 -0.1 0.04 -0.05 l- -0.01 0.01 0 -0.1 -0.2 0 ls 0.1 0.03 0.01 -0.1 0.1 300 -0.03 -0.02 -0.01 0.02 -0.04 0 0.05 0 -0.03 0.04 0.1 -0.1 -0.05 0.05 0.2 0.2 -0.2 0.03 0 250 0.1 0.3 -0.01 0 -0.3 0 0 0 -0.02 0.02 0 -0.1 -0.4 0.01 0.4 -0.2 0 0.4 0.01 0.05 -0.01 -0.05 200 -0.05 0 Demodulation Phase of f2 -0.01 -0.02 -0.2 0.1 0.02 -0.3 0.3 -0.4 -0.3 0 -0.1 0.1 0 0.03 0.02 -0.1 0.01 -0.03 0.04 0.3 150 0.2 0.01 0.2 -0.04 -0.1 -0.2 -0.03 0.05 -0.01 0.1 0.1 0.03 -0.1 0.04 0.1 0.02 0 0 0 -0.02 -0.02 0 0 100 -0.04 0.1 0.03 0.05 -0.05 -0.05 0 -0.03 -0.2 -0.1 0.2 0.01 -0.01 0 -0.1 -0.3 0 0 0 -0.02 0.02 50 0.3 0.4 -0.3 0.2 0 -0.2 -0.4 0 0.01 -0.01 -0.4 0.05 0.01 0 0.1 -0.01 -0.05 0 0.05 0 0 -0.02 0.1 0.3 0.02 0 0 50 100 150 200 250 300 350 Demodulation Phase of f1 40m Original design of SP DDM +33 : off-resonant -33 : off-resonant +166: resonant -166 : anti-resonant +33resonance • l+ and ls plot separated • Difficult to find PRM position without carrier Abs +166resonance Design Lock point SP33 Lock point 0.56degree LSC meeting at LLO, March 2005

7. Double Demodulation at SP 0 0 0 0 0 0 0 350 0 dc=0 0 0.04 -0.04 -0.06 0.06 l+ 0.1 -0.1 -0.04 0 0.04 l- -0.05 0.1 0.02 0.05 -0.2 0.05 -0.02 0.2 ls 0.2 300 -0.1 -0.3 -0.02 0.3 0.02 0 0 0 0 0 0.1 -0.02 0.02 -0.1 250 -0.2 -0.3 0.04 -0.05 0.3 0 0.1 -0.2 -0.04 -0.05 -0.1 0.05 0.2 0.06 -0.02 0.05 0 200 -0.1 Demodulation Phase of f2 0.1 0 -0.04 0.06 0.02 0 0.02 0 0 0 0 0 0 0.04 -0.02 -0.06 -0.1 -0.1 0 150 0.04 0.1 -0.05 0.05 0.1 -0.05 -0.04 -0.2 0.2 0.3 0 0.02 -0.3 -0.02 0.2 100 0 -0.1 -0.02 0.1 0 -0.3 0 0.02 0.02 0.05 0.3 50 -0.1 0 -0.05 -0.2 0 0 0.05 0.04 -0.1 -0.02 0.1 -0.04 -0.2 0.2 -0.04 -0.02 0.04 -0.06 0.06 0.1 0 0 0 50 100 150 200 250 300 350 Demodulation Phase of f1 Offset l+ +0.56 deg, ls +0.56 deg +33 : resonant -33 : resonant +166: resonant -166 : anti-resonant +33resonance • l+ and ls plot overlapping • DC line changed • Easy to find PRM position using 33MHz resonance • Like AdLIGO configuration • Carrier would be off resonant Abs +166resonance Design Lock point SP33 Lock point 0.56degree LSC meeting at LLO, March 2005

8. 40m vs. Ad-LIGO 40m x6 x1.5 x3 Ad-LIGO x2 x8 x17 LSC meeting at LLO, March 2005

9. Struggling lock acquisition for Arms Problems • Sideband resonance on arm cavities • Resonant point shift due to detuned SRC • 16kHz sampling rate is too slow for 40m. • Coupling between X arm and Y arm LSC meeting at LLO, March 2005

10. ETMy ETMy Sideband resonance Shutter Shutter ITMy ITMy PRM ETMx ITMx PRM BS ETMx ITMx BS Shutter Shutter SRM SRM Carrier 33MHz 166MHz ETMy ETMy ITMy ITMy PRM ETMx ITMx PRM ETMx ITMx BS BS SRM SRM Which is first ? DRMI lock or Arms lock? • Carrier flash does not matter because DRMI is locked by DDM (beat of sidebands). • Sideband flash matters. • Can keep locking ~10sec with lower gain. DRMI first DDM Arms first • PRFPMI : succeeded • RSE : not succeeded! • Because of resonant point shift due to detuned SRC Normalized by PRC power LSC meeting at LLO, March 2005

11. Resonant point shift • Resonant point shifts in single arm lock because of carrier phase change in detuned SRC Abs LSC meeting at LLO, March 2005

12. Digital sampling for 40m RSE configuration • Due to large seismic motion, 3x10-6m at 1Hz assumed here • Due to very high combined finesse of arm and PRC ~18000. • Night is about 10 times better but still not enough. • Needs wider linear error signal. • Normalization technique to widen linear range • Slower mirror motion Abs LSC meeting at LLO, March 2005

13. Off-resonant lock scheme for arm cavity • Error signal is produced by transmitted light as • to avoid coupling through carrier in central part, • to widen linear range. Resonant Lock Off-resonant Lock point LSC meeting at LLO, March 2005

14. Arm power Xarm lock Yarm lock Error signal Offset lock Offset lock Ideal lock point Off resonant Arm lock with DRMI DRMI with single arm lock • Not so difficult • Last ~10 min • Lock acquisition time ~1 min • Switched to POX/POY signal normalized by transmitted light • Full carrier was stored in each arm cavity separately. Both arms lock with DRMI • Off-resonant carrier on arm cavities • Last < 1 min • Locked only 2 times LSC meeting at LLO, March 2005

15. Coupling between Lx and Ly CARM/DARM lock Common of arms(CARM) Differential of arms(DARM) Power recycling cavity Michelson Signal recycling cavity : L=(Lx Ly) / 2 : L=Lx Ly : l=(lx ly) / 2 : l=lx ly : ls=( lsx lsy) / 2 ETMy POX/POY lock Ly ITMy POY lsy ETMx Laser ly ITMx PRM BS lx Lx lsx POX SRM PO SP • Coupling is 94% when carrier is resonant. • Off-resonant lock for arms AP LSC meeting at LLO, March 2005

16. The way to RSE Arm lock first with offset using transmitted light DRMI lock first using DDM Resonant point shift Clear sampling Problem and linear range problem Both arms lock with offset using transmitted light Switch to POX/POY signal with the offset Switch to CARM/DARM signal with the offset Coupling between Lx and Ly Reduce offset Full RSE lock LSC meeting at LLO, March 2005

17. Way from off-resonant lock to com/diff lock Off-resonant Lock point Abs +/-0.2nm LSC meeting at LLO, March 2005

18. Normalized SP166 for CARM Off-resonant Lock point Abs +/-0.2nm Dem.phase accuracy ~10degre for 166MHz ~0.1degree for 33MHz LSC meeting at LLO, March 2005

19. ETMY ITMY ITMX ETMX PRM BS SRM e2e SIMULATION:4Om/AdvLIGO package optical configuration IFO with Arms IFO Central part LSC meeting at LLO, March 2005

20. e2e SIMULATION:4Om/AdvLIGO package • E2E validation of DC fields comparing with TWIDDLE results: good agreement ! • E2Etransfer functions simulations (and comparison with TWIDDLE ones) of DOF at SP, AP and PO shaking the end mirrors with white noise • at different demodulation frequencies : • (33,133,166,199) MHz I signal E2E TWIDDLE E2E Q signal TWIDDLE Example: DARM @ AP166 MHz TWIDDLE and E2E comparison