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

2. 40m Progress, LSC meeting, Mar. 2004
l+ signal calculated by Twiddle on Conceptual Design of the 40 meter Conceptual Design of the 40 meter (T 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

3. 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

4. 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

5. 40m Progress, LSC meeting, Mar. 2004
Signal matrix
Original signal matrix
Signal matrix with sideband of sideband
40m Progress, LSC meeting, Mar. 2004

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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