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

LIGO-G W 2 LIGO I design requirements circa 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

LIGO-G W 3 Present PSL/IOO optical layout

LIGO-G W 4 Example power budget

LIGO-G W 5 Present H1 power budget

LIGO-G W 6 Present H2 power budget

LIGO-G W 7 Present L1 power budget

LIGO-G 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

LIGO-G W 9 Proposed upstream PSL layout changes

LIGO-G W 10 PMC transmission vs. mirror losses

LIGO-G W 11 Expected H1 budget with only ‘outside’ improvements

LIGO-G W 12 Expected H1 budget if MC mirrors are also replaced

LIGO-G W 13 Expected H2 budget with only ‘outside’ improvements

LIGO-G W 14 Expected H2 budget if Faraday isolator is also replaced

LIGO-G W 15 Options for increasing the input laser power above the 11 W level Rebuild the 126MOPA at LTW to 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.