1. LIGO- G050004-00-R 40m weekly meeting, Jan 05, 2005 1 Explore demodulation phase for DDM on 40m RSE prototype Osamu Miyakawa, Caltech LIGO-G050004-00-R

2. 40m weekly meeting, Jan 05, 2005 2 Setup ITMy ITMx BS PRM SRM Laser SP33 SP DDM Carrier 33MHz 166MHz  Signal for l + is extracted from Symmetric Port (SP).  SP33 is a 33MHz single demodulation PD used for lock acquisition.  Then it switches to SP DDM (double demodulation).  We assume that l s and l - are locked.

3. LIGO- G050004-00-R 40m weekly meeting, Jan 05, 2005 3 SP33,DDM,+/-33M,+/-166M@SP Abs Design Lock point SP33 Lock point 0.56 degree +166resonance +33 resonance +33 off-resonance

4. LIGO- G050004-00-R 40m weekly meeting, Jan 05, 2005 4 Original design (no offset) Abs Design Lock point SP33 Lock point 0.56degree +166resonance +33resonance +33 : off-resonant -33 : off-resonant +166: resonant -166 : anti-resonant l + and l s plot separated Difficult

5. LIGO- G050004-00-R 40m weekly meeting, Jan 05, 2005 5 l + +0.56 degree, l s +0.56 degree Abs Design Lock point SP33 Lock point 0.56degree +166resonance +33resonance +33 : resonant -33 : resonant +166: resonant -166 : anti-resonant l + and l s plot overlapping DC line changed Easy (if l + is moved, servo try to move l s.)

6. LIGO- G050004-00-R 40m weekly meeting, Jan 05, 2005 6 l + +0.56 degree Abs Design Lock point SP33 Lock point 0.56degree +166resonance +33resonance +33 : resonant -33 : resonant +166: off-resonant -166 : anti-resonant l + and l s plot overlapping DC line changed Difficult

7. LIGO- G050004-00-R 40m weekly meeting, Jan 05, 2005 7 l s +0.56 degree, Abs Design Lock point SP33 Lock point 0.56degree +166resonance +33resonance +33 : off-resonant -33 : off-resonant +166: resonant -166 : anti-resonant l + and l s plot separated Same DC line Difficult

8. LIGO- G050004-00-R 40m weekly meeting, Jan 05, 2005 8 Exploring phase  Lock l + to SP33.  Adjust gain during SP33, SP133 and SP199.  Find maximum l + signal on SP133 and SP199.  Move to DC=0 line.  Add calculated phase on SP133 and SP199.  Add offset on SP33 until SP DDM has no offset.  Switch SP33 to DDM.

9. LIGO- G050004-00-R 40m weekly meeting, Jan 05, 2005 9 40m vs. Ad-LIGO 40m Ad-LIGO x6 x2

10. LIGO- G050004-00-R 40m weekly meeting, Jan 05, 2005 10 Summary  Off-resonance of 33MHz makes good signal separation between l + and l s.  We can find a way to optimize demodulation phase for DDM at SP, which has good signal separation and no offset.  Ad-LIGO using 9-180MHz sidebands has less signal separation between l + and l s, but better signal separation for l - and l s