Effect of sideband of sideband on 40m and Advanced LIGO Osamu Miyakawa, Caltech LIGO-G040311-00-R 40m Progress, LSC meeting, Mar. 2004

40m Progress, LSC meeting, Mar. 2004 l+ signal calculated by Twiddle on Conceptual Design of the 40 meter Conceptual Design of the 40 meter (T010115-00-R) l+ signal Calculated by FINESS -150 -100 -50 50 100 150 -0.01 -0.008 -0.006 -0.004 -0.002 0.002 0.004 0.006 0.008 0.01 l+ Error Signal No-arm detuned RSE, DDM at SP, phase1=189, phase2=33 (dc=0) l+ signal of DDM has a big offset when it is not resonant in both cases. However no offset on real signal at all. 40m Progress, LSC meeting, Mar. 2004

40m Progress, LSC meeting, Mar. 2004 Sideband of sideband Simulation Real world 166MHz Sideband is produced on existing 33MHz sideband with two serial EOM. Sideband of sideband is amplitude modulation with 180degree phase offset against carrier. Beat between carrier and f2+/-f1 produces signal with unbalanced sideband by detuned cavity. 40m Progress, LSC meeting, Mar. 2004

l+ signal with sideband of sideband Carrier resonance No offset No offset Big disturbance by carrier Some small disturbance 40m Progress, LSC meeting, Mar. 2004

40m Progress, LSC meeting, Mar. 2004 Signal matrix Original signal matrix Signal matrix with sideband of sideband 40m Progress, LSC meeting, Mar. 2004

SP contour plot for l+ signal No sideband of sideband With sideband of sideband 50 100 150 200 250 300 350 Demodulation Phase of f1 Demodulation Phase of f2 Double Demodulation at SP -0.4 -0.3 -0.2 -0.1 0.1 0.2 0.3 0.4 -0.04 -0.03 -0.02 -0.01 0.01 0.02 0.03 0.04 -0.05 0.05 dc=0 l+ l- ls 50 100 150 200 250 300 350 Demodulation Phase of f1 Demodulation Phase of f2 Double Demodulation at SP -0.4 -0.3 -0.2 -0.1 0.1 0.2 0.3 0.4 -0.04 -0.03 -0.02 -0.01 0.01 0.02 0.03 0.04 -0.05 0.05 dc=0 l+ l- ls No big difference? 40m Progress, LSC meeting, Mar. 2004

PO contour plot for ls signal No sideband of sideband With sideband of sideband 50 100 150 200 250 300 350 Demodulation Phase of f1 Demodulation Phase of f2 Double Demodulation at PO -2 -1.5 -1 -0.5 0.5 1 1.5 2 -0.4 -0.2 0.2 0.4 dc=0 l+ l- ls 50 100 150 200 250 300 350 Demodulation Phase of f1 Demodulation Phase of f2 Double Demodulation at PO -1.5 -1 -0.5 0.5 1 1.5 -0.4 -0.2 0.2 0.4 -2 2 dc=0 l+ l- ls Offset line changed. 40m Progress, LSC meeting, Mar. 2004

AP contour plot for l- signal No sideband of sideband With sideband of sideband 50 100 150 200 250 300 350 Demodulation Phase of f1 Demodulation Phase of f2 Double Demodulation at AP -0.03 -0.02 -0.01 0.01 0.02 0.03 -0.008 -0.006 -0.004 -0.002 0.002 0.004 0.006 0.008 dc=0 l+ l- ls 50 100 150 200 250 300 350 Demodulation Phase of f1 Demodulation Phase of f2 Double Demodulation at AP -0.03 -0.02 -0.01 0.01 0.02 0.03 -0.008 -0.006 -0.004 -0.002 0.002 0.004 0.006 0.008 dc=0 l+ l- ls No big difference 40m Progress, LSC meeting, Mar. 2004

40m Progress, LSC meeting, Mar. 2004 Summary Sideband of sideband was not discussed when 40m and AdLIGO were designed. Sideband of sideband introduce a new disturbance because of the beat between carrier and f1+/-f2 Signal matrix is worse than before. Lock acquisition problem Carrier resonance of PRC and SEC Carrier resonance of the arm 40m Progress, LSC meeting, Mar. 2004

40m Progress, LSC meeting, Mar. 2004 What should we do? Continue this optical setting with sideband of sideband? Change experimental setup to avoid sideband of sideband? 40m Progress, LSC meeting, Mar. 2004

To avoid sideband of sideband Mach Zender interferometer One more control Mode matching, same length, Alignment again 2 more EOM to kill 133MHz and 199MHz Need to adjust phase and amplitude Apply Voltage to existing EOM with 133MHz and 199MHz to kill sideband of sideband Using resonant type EOM?? 40m Progress, LSC meeting, Mar. 2004