1. AIGO 2K Australia - Italy Workshop 2005 7 th October 2005 7 th October 2005 Pablo Barriga for AIGO group

2. ACIGA Mission  High Optical Power Test Facility  Low noise 80m base line advanced interferometer  Advanced gravitational wave interferometer (AIGO)  Primary Institutions: University of Adelaide Australian National University University of Western Australia Affiliate Institutions: Monash University CSIRO-Optics Development of high power optics in collaboration with LIGO Demonstrate noise performance of high power interferometer First in the Southern Hemisphere

3. Vacuum System Single increment 3.5m high vacuum tanks 400mm diameter pipes? (R. De Salvo)

4. Input Laser  Injection locked 10W Nd:YAG laser has been developed by The University of Adelaide.  High power laser clean room near Class 100.  Future laser >100W Talk by Peter Veitch

5. High Optical Power Mode Cleaner  Astigmatism and thermal lensing calculations.  Isolation system transfer function shows good performance.  Control system design and implementation underway. X - Axis Y - Axis

6. Test Masses Fused Silica or Sapphire? Start with small test masses ~10kg Second stage 40kg (Advanced LIGO) Sapphire Input Test Mass Rayleigh Scattering Measurements Talk by Zewu Yan

7. Suspension System Stage 1: Niobium Flexures  Stage 2 : Fused Silica Flexures Talk by Ben Lee

8. Isolation System Talk by Jean Charles and Eu-Jeen  Robust isolation system  Built for heavy test masses

9. Digital Control  Digital Control already under development.  DSP based?  LIGO EPICS?  Is there a way of combining both?

10. AIGO Dual Recycling Interferometer M1 M2 M3 To Detector Bench South Fabry - Perot Cavity East Fabry - Perot Cavity Mode Cleaner 100W PSL Nd:YAG laser = 1064nm East - end Station South - end Station Main Building Signal Recycling Mirror Beam Splitter Power Recycling Cavity N

11. Mode-Cleaner Geometry M1 M2 M3 l 1  200mm 2wo2wo l 2  9900mm Incident angle 44.712 o Incident angle 0.579 o Concave end mirror Flat Mirrors used as input and output couplers

12. Coating and Substrate Absorptions High reflectivity coating absorption produces astigmatic thermal lensing. The spot ellipticity produce different distribution between X and Y axis. M2 used as output coupler the diagonally transmitted beam produces strong astigmatic thermal lensing.

13. 020406080100120140160180200 0 0.02 0.04 0.06 Input Power [W] Eccentricity M3 Spot Waist Size Input Power [W] 020406080100120140160180200 0 0.02 0.04 0.06 Eccentricity M3 Spot Waist Size Eccentricity variation with Power 020406080100120140160180200 0 0.02 0.04 0.06 Eccentricity M3 Spot Waist Size Eccentricity variation with Power M1/M2 = Flat M3 = 22.5 m M1/M2 = 1000 m M3 = 23.3 m M1/M2 = 470 m M3 = 23.3 m

14. AIGO Future Interferometer M1 M2 M3 To Detector Bench South Fabry - Perot Cavity East Fabry - Perot Cavity Mode Cleaner 100W PSL Nd:YAG laser = 1064nm East - end Station South - end Station Main Building Signal Recycling Mirror Beam Splitter Power Recycling Cavity N

15. AIGO Future Interferometer M1 M2 M3 To Detector Bench South Fabry - Perot Cavity East Fabry - Perot Cavity Mode Cleaner 100W PSL Nd:YAG laser = 1064nm East - end Station South - end Station Main Building Signal Recycling Mirror Beam Splitter Power Recycling Cavity N

16. AIGO Future Interferometer M1 M2 To Detector Bench South Fabry - Perot Cavity East Fabry - Perot Cavity Mode Cleaner 100W PSL Nd:YAG laser = 1064nm East - end Station South - end Station Main Building Signal Recycling Mirror Beam Splitter Power Recycling Cavity N M3

17. M1 M2 M3 To Detector Bench South Fabry-Perot Cavity East Fabry-Perot Cavity Mode Cleaner 100W PSL Nd:YAG laser = 1064nm ETM SRM BS PRM ITM L1L1 L2L2 l1l1 l2l2 l sr l pr L MC AIGO Future Interferometer

18. To Detector Bench South Fabry-Perot Cavity East Fabry-Perot Cavity ETM SRM BS PRM ITM L1L1 L2L2 l1l1 l2l2 l sr l pr AIGO Future Interferometer Carrier: Resonant in PRC and Arms RF Sideband f1: Resonant in PRC RF Sideband f2: Resonant in PRC and SRC

19. Actual Interferometer Configuration Cavities Length L MC = 10 m L PRC = 12 m L Arms = 2000 m L SRC = 12 m South End Station East End Station

20. AIGO Proposed Configuration Cavities Length L MC = 10 m L PRC = 3.6 m L Arms = 2007 m L SRC = 3.6 m South End Station East End Station

21. Rule of Thumb Carrier should be resonant in the arms and the PRC. Carrier resonant in the SRC for resonant sideband extraction (RSE), and anti-resonant for signal recycling. SB1 should be nearly anti-resonant in the arms, and resonant in the PRC. SB2 also nearly anti-resonant in the arms, and resonant in the PRC. One of the SB should be resonant in the SRC and the other nearly anti-resonant.

22. Limiting values for the cavities length are defined by the vacuum envelop: Integer ratios between the cavities are not recommended, in order to avoid harmonics sidebands to resonate in the recycling cavity. AIGO Constrains

23. Actual Configuration Length PRC = 11727 mm  Mode Cleaner shorter than Recycling Cavities? PRC Free Spectral Range: 12.782 MHz PRC as a coupled cavity  half integer of PRC FSR “Longest” Mode Cleaner 7818 mm  FSR = 19.173 MHz

24. For transmission of modulation sidebands by the mode-cleaner, L MC and f m must satisfy: For sideband coupling into the recycling cavity, L PRC and f m must satisfy: AIGO Interferometer Sidebands Sideband must not resonate inside the main arms, but also not exactly anti-resonant: Sideband 1 = 19.173 MHz n 1 = 1 n 2 = 1 n 3 = 255.82

25. To choose the high frequency sideband we look to demodulate at: Schnupp asymmetry given by: AIGO Interferometer Sidebands For a peak frequency of 300Hz (Adv LIGO) the carrier phase shift will be: Sideband 2 = 172.559 MHz  l = 434 mm L SRC = 12569 mm

26. Proposed Configuration Length PRC = 4450 mm PRC Free Spectral Range: 33.685 MHz PRC as a coupled cavity  half integer of PRC FSR “Longest” Mode Cleaner 8900 mm  FSR = 16.842 MHz

27. For transmission of modulation sidebands by the mode-cleaner, L MC and f m must satisfy: For sideband coupling into the recycling cavity, L PRC and f m must satisfy: AIGO Interferometer Sidebands Sideband must not resonate inside the main arms, but also not exactly anti-resonant: Sideband 1 = 16.842 MHz n 1 = 1 n 2 = 0 n 3 = 225.55

28. To choose the high frequency sideband we look to demodulate at: Schnupp asymmetry given by: AIGO Interferometer Sidebands For a peak frequency of 300Hz (Adv LIGO) the carrier phase shift will be: Sideband 2 = 168.423 MHz  l = 445 mm L SRC = 5313 mm

29. Adv LIGOVIRGOAIGO 2K (sh)AIGO 2K (lg) PRM - BS461.8 BS - ITM Inline 4.5366.42.87310.144 BS - ITM Perp 4.1195.62.4279.71 L_PRC Inline 8.53612.44.67311.944 L_PRC Perp 8.11911.64.22711.510 SRM - BS4.8215.5622.6632.642 AIGO, Adv LIGO and VIRGO

30. Adv LIGOVIRGOAIGO 2K (sh)AIGO 2K (lg) L_MC16.656143.528.97.818 L_PRC8.32811.964.4511.727 L_Arms4000300020072000 L_SRC9.14811.5625.31312.569 Asymmetry0.4160.3990.4450.434 SB 1 (MHz)96.2716.8419.17 SB 2 (MHz)180188168.42172.56 AIGO, Adv LIGO and VIRGO

31. ©LIGO Scientific Collaboration Newtonian background Seismic ‘cutoff’ Suspension thermal noise Test mass thermal noise Unified quantum noise 10 Hz100 Hz 1 kHz 10 -22 10 -24 10 -21 10 -23 Initial LIGO Advanced LIGO Newtonian Seismic Suspension Test Mass Quantum Frequency [Hz] h(f) [1/√Hz] High Optical Power

32. ©LIGO Scientific Collaboration Newtonian background Seismic ‘cutoff’ Suspension thermal noise Test mass thermal noise Unified quantum noise 10 Hz100 Hz 1 kHz 10 -22 10 -24 10 -21 10 -23 Initial LIGO Advanced LIGO Newtonian Seismic Suspension Test Mass Quantum Frequency [Hz] h(f) [1/√Hz] High Optical Power AIGO 2K

33. Conclusions  AIGO 2K Dual Recycling Interferometer  Test masses Fused Silica or Sapphire?  Digital control system. EPICS, DSP or both?  Short or long Recycling Cavities?

34. Conclusions More information at: ACIGA http://www.anu.edu.au/Physics/ACIGA/ Australian National University http://www.anu.edu.au/Physics/ACIGA/ANU/ University of Adelaide http://www.physics.adelaide.edu.au/optics/res/hi_powerc.html University of Western Australia http://www.gravity.pd.uwa.edu.au/