1. LIGO-G030695-00-W 1 Increasing the laser power incident on the recycling mirrors Doug Cook and Rick Savage LIGO commissioning meeting Dec. 22, 2003 Ref. LIGO-T030288-00-W

2. LIGO-G030695-00-W 2 LIGO I design requirements circa 1995 6 watts of laser power incident on the recycling mirror 8.5 watts of laser power delivered to the IOO subsystem 10 watts of laser power delivered by the 126MOPA laser (Lightwave) »In a circular TEM 00 mode

3. LIGO-G030695-00-W 3 Present PSL/IOO optical layout

4. LIGO-G030695-00-W 4 Example power budget

5. LIGO-G030695-00-W 5 Present H1 power budget

6. LIGO-G030695-00-W 6 Present H2 power budget

7. LIGO-G030695-00-W 7 Present L1 power budget

8. LIGO-G030695-00-W 8 Options for improvement outside of the vacuum system Increase 126MOPA power »Rebuild at Lightwave (LTW) to original specification. –Doesn’t include NPRO »Modify upstream PSL layout to facilitate swapping lasers –Mount phase-correcting EOM outside laser head –Add /2 plate and polarizer to set power to FSS and PMC paths –Modematch upstream of FSS/PMC splitter Mount PMC inside a vacuum chamber »Reduce mirror losses from hundreds to ~ 50 ppm Implement single EOM modulation scheme »Eliminate two EOMs from beam path

9. LIGO-G030695-00-W 9 Proposed upstream PSL layout changes

10. LIGO-G030695-00-W 10 PMC transmission vs. mirror losses

11. LIGO-G030695-00-W 11 Expected H1 budget with only ‘outside’ improvements

12. LIGO-G030695-00-W 12 Expected H1 budget if MC mirrors are also replaced

13. LIGO-G030695-00-W 13 Expected H2 budget with only ‘outside’ improvements

14. LIGO-G030695-00-W 14 Expected H2 budget if Faraday isolator is also replaced

15. LIGO-G030695-00-W 15 Options for increasing the input laser power above the 11 W level Rebuild the 126MOPA at LTW to 15-20 level »LTW technicians have indicated this is feasible »May have been demonstrated in another LTW product Replace the PA pump diodes with higher power units »LTW has identified new vendor and are starting to use them in another product (Model 6000?). Stability issues? Add a second amplifier head after the 126MOPA »Stanford has tested this configuration for Adv. LIGO PSL development work Accelerate procurement of Adv. LIGO laser from Hannover/LZH.