1 Laser Frequency Stabilization – 2004, May 04
Laser Frequency Stabilization
François BONDU CNRS – ARTEMIS, Nice VIRGO
• How it works (Design)• Make it work (experimental work)• Noise performances• Next activities
2 Laser Frequency Stabilization – 2004, May 04
Complete Design in 2002 - early 2003
Designed to meet the requirements in the 10 Hz – 10 kHz band,Starting from the requirements.
Design written, in Virgo Notes:
Requirements for second stage VIR-NOT-OCA-1390-227Advanced digital filters VIR-NOT-OCA-1390-233Multiple servo loop systems VIR-NOT-OCA-1390-234Description of the loops VIR-NOT-OCA-1390-247
THIS design functionalities successfully tried on the north arm this month
HOW IT WORKS - DESIGN
3 Laser Frequency Stabilization – 2004, May 04
HOW IT WORKS - DESIGN
MC
laser
Clas Clas2
CMC
CEM
OVERVIEW
ITF Common mode- or north arm -
4 Laser Frequency Stabilization – 2004, May 04
HOW IT WORKS - DESIGN
MC
laser
Clas Clas2
CMC
2nd stage
CEM
Pr_B1(p)_ACp
Sc_IB_SSFS_Corr
Bs_IMC_DR_AC1
Second stage of frequency stabilization
5 Laser Frequency Stabilization – 2004, May 04
HOW IT WORKS - DESIGN
MC
laser
Clas Clas2
CMC
Pre-stabilization
CEM
Bs_IMC_DR_AC1
Bs_ML_Pz
First stage of frequency stabilization(pre-stabilization)
6 Laser Frequency Stabilization – 2004, May 04
HOW IT WORKS - DESIGN
MC
laser
Clas Clas2
CMC
IMC
CEM
Sc_IB_SSFS_Corr
Sc_MC_zCorrR
Bs_IMC_DR_AC1
IMC locking
7 Laser Frequency Stabilization – 2004, May 04
HOW IT WORKS - DESIGN
MC
laser
Clas Clas2
CMC
CEM
Sc_NE_zGc
Sc_IB_zErrGC
ITF Common mode DC control
8 Laser Frequency Stabilization – 2004, May 04
HOW IT WORKS - DESIGN
MODEL
« frequcncy noise » inputs
Stabilized laser frequency
Free running laser noise
IB or MC motion
Reference cavity length noise
9 Laser Frequency Stabilization – 2004, May 04
HOW IT WORKS - DESIGN
SIMULINK MODEL
With radiation pressure
10 Laser Frequency Stabilization – 2004, May 04
HOW IT WORKS - DESIGN
Note on alternative topology (‘topo #1’)
MC
laser
Clas Clas2
CMC
CEM
Sc_NE_zGc
Sc_IB_zErrGC
11 Laser Frequency Stabilization – 2004, May 04
ITF DC control necessary
reference cavity can not change its frequency easily=> ‘bad’ configuration (two loops sharing a same error signal)=> second stage can not have DC gain
Is not demonstrated to meet the requirements
See talks of april 2002, nov 2003
Would have been a deceiving solution, according to today knowledge
HOW IT WORKS - DESIGN
Note on alternative topology (‘topo #1’)
12 Laser Frequency Stabilization – 2004, May 04
- « 170 Hz » issue (december 2003)
- analysis work
- lock acquisition
- transient during the lock acquisition / unlock of IMC
- transient for lock with B1 / algo in Gc
- resonances in the MC suspension
Experimental work
13 Laser Frequency Stabilization – 2004, May 04
Oscillation – saturation at about 170 Hz
zGc not « hold »
Experimental work (1)
14 Laser Frequency Stabilization – 2004, May 04
Leak-through due to phase modulationvia IMC motion (cf. H. Trinquet)VIR-NOT-OCA-1390-178Cf. also gouaty_09Nov03_sens.ppt
Stability of second stage:crossing of these two TFs
Experimental work (1)
SUSPICION:
15 Laser Frequency Stabilization – 2004, May 04
Experimental work (1)
Leak-through
16 Laser Frequency Stabilization – 2004, May 04
• Made the calculations taking into account this effect:=> loop stable
• The problem was a loop oscillationtoo much gain, due to the « horns » in the laser frequency noise
Experimental work (1)
17 Laser Frequency Stabilization – 2004, May 04
Experimental work (2)
18 Laser Frequency Stabilization – 2004, May 04
Experimental work (2)SSFS_763560321_1.gifSSFS_763560321_2.gifSSFS_763561763_1.gifSSFS_763561763_2.gifSSFS_763561763_3.gifSSFS_763561763_4.gifSSFS_763566197_1.gifSSFS_763566896_1.gifSSFS_763575387_1.gifSSFS_763575387_2.gifSSFS_763575387_3.gifSSFS_763633937_1.gifSSFS_763633937_2.gifSSFS_763633937_3.gifSSFS_763633937_4.gifSSFS_763633937_5.gifSSFS_763643300_1.gifSSFS_763643300_2.gifSSFS_763643300_3.gifSSFS_763643301_1.gifSSFS_763647965.gifSSFS_763649282.gifSSFS_763649282_1.gifSSFS_763650999.gifSSFS_763726087.gifSSFS_763726087_2.gifSSFS_763726087_3.gifSSFS_763730743_1.gifSSFS_763730743_2.gifSSFS_763730743_3.gifSSFS_764023082_1.gifSSFS_764023082_2.gifSSFS_764023082_3.gifSSFS_764023082_4.gifSSFS_764023082_5.gifSSFS_764025420_1.gifSSFS_764025420_2.gifSSFS_764107509_1.gifSSFS_764107509_2.gifSSFS_764109486.gifSSFS_764109945.gifSSFS_764109945_2.gifSSFS_764110790.gifSSFS_764112941_1.gifSSFS_764114400_1.gif
SSFS_764114409.gifSSFS_764184989.gifSSFS_764191160.gifSSFS_764191160_2.gifSSFS_764191160_3.gifSSFS_764191160_4.gifSSFS_764198517_1.gifSSFS_764237811.gifSSFS_764237811_2.gifSSFS_764240101.gifSSFS_764240101_2.gifSSFS_764242950_1.gifSSFS_764242950_2.gifSSFS_764255788.gifSSFS_764255788_3.gifSSFS_764257611_1.gifSSFS_764257611_2.gifSSFS_764257611_3.gifSSFS_764257611_4.gifSSFS_764332843_1.gifSSFS_764343670_1.gifSSFS_764343670_2.gifSSFS_764344270.gifSSFS_764344270_2.gifSSFS_764344706.gifSSFS_764344733.gifSSFS_764589302.gifSSFS_764589459_1.gifSSFS_764589459_2.gifSSFS_764589459_3.gifSSFS_764589459_4.gifSSFS_764589459_5.gifSSFS_764665294.gifSSFS_765302566_1.gifSSFS_765302566_2.gifSSFS_765302705_1.gifSSFS_765308183_1.gifSSFS_765308183_2.gifSSFS_765311654_1.gifSSFS_765311710_1.gifSSFS_765311732_1.gifSSFS_765318312_1.gifSSFS_765320955.gifSSFS_765327588.gifSSFS_765398187.gif
SSFS_765398187_2.gifSSFS_765398305_1.gifSSFS_765398305_2.gifSSFS_765398306_1.gifSSFS_765398306_2.gifSSFS_765398306_3.gifSSFS_765398306_4.gifSSFS_765398306_5.gifSSFS_765475670.gifSSFS_765479098.gifSSFS_765484281.gifSSFS_765485180.gifSSFS_765485500.gifSSFS_765485500_2.gifSSFS_765536392.gifSSFS_765536392_2.gifSSFS_765545485.gifSSFS_765545485_2.gifSSFS_765549504.gifSSFS_765549517.gifSSFS_765549540.gifSSFS_765552348.gifSSFS_765968820.gifSSFS_765971138.gifSSFS_765971138_2.gifSSFS_766144998.gifSSFS_766149536.gifSSFS_766150426.gifSSFS_766150430.gifSSFS_766150558.gifSSFS_766151638.gifSSFS_766151639.gifSSFS_766417300.gifSSFS_766417306.gifSSFS_766417306_2.gifSSFS_766417436.gifSSFS_766426403.gifSSFS_766426460.gifSSFS_766426497.gifSSFS_766426552.gifSSFS_766430777.gifSSFS_766431882.gifSSFS_766466742.gifSSFS_766590206.gifSSFS_766709295.gif
SSFS_766709295_2.gifSSFS_766712859.gifSSFS_766772044.gifSSFS_766779324.gifSSFS_766783915.gifSSFS_766784545.gifSSFS_COHE_765321000_1.gifSSFS_COHE_766713000_SSFSCorr_GxIB.gifSSFS_COHE_766713000_SSFSCorr_GxMC.gifSSFS_COHE_766713000_SSFSCorr_IBLCtx.gifSSFS_COHE_766713000_SSFSCorr_IBLCtytz.gifSSFS_COHE_766713000_SSFSCorr_ISYSAA.gifSSFS_COHE_766990000_PrRFCACp_ScNEzGC.gifSSFS_Calib_HG.gifSSFS_Calib_HG2.gifSSFS_Calib_LG.gifSSFS_FFT_763633900.gifSSFS_FFT_763633937_1.gifSSFS_FFT_763633937_2.gifSSFS_FFT_763633937_3.gifSSFS_FFT_763643302_1.gifSSFS_FFT_764113906.gifSSFS_FFT_764114430_1.gifSSFS_FFT_764114500_1.gifSSFS_FFT_764114500_B1pd1ACp.txtSSFS_FFT_764114500_SSFSCorr.txtSSFS_FFT_764589420.gifSSFS_FFT_764590250.gifSSFS_FFT_764597900.gifSSFS_FFT_765321000_B1pd1ACp.txtSSFS_FFT_765321000_SSFSCorr.txtSSFS_FFT_765489291_B1pd1ACp.txtSSFS_FFT_765489291_SSFSCorr.txtSSFS_FFT_765549800.gifSSFS_FFT_765549800_10.gifSSFS_FFT_765549800_11.gifSSFS_FFT_765549800_12.gifSSFS_FFT_765549800_2.gifSSFS_FFT_765549800_3.gifSSFS_FFT_765549800_4.gifSSFS_FFT_765549800_5.gifSSFS_FFT_765549800_6.gifSSFS_FFT_765549800_7.gifSSFS_FFT_765549800_8.gifSSFS_FFT_765549800_9.gif
SSFS_FFT_765549800_RFCACp.txtSSFS_FFT_766456300.gifSSFS_FFT_766456300_B1pd1ACp.txtSSFS_FFT_766456300_SSFSCorr.txtSSFS_FFT_766467000.gifSSFS_FFT_766467000_B1pd1ACp.txtSSFS_FFT_766467000_SSFSCorr.txtSSFS_FFT_766713000_B1ACp.txtSSFS_FFT_766713000_B1d6ACp.txtSSFS_FFT_766713000_B1d6_SSFSCorr.gifSSFS_FFT_766713000_RFC.gifSSFS_FFT_766713000_RFC_2.gifSSFS_FFT_766713000_RFC_3.gifSSFS_FFT_766713000_RFC_4.gifSSFS_FFT_766713000_SSFSCorr.txtSSFS_FFT_766713000_zErrGC_2.txtSSFS_FFT_766713000_zErrGCx30_2.txtSSFS_FFT_766713100_zErrGC.txtSSFS_FFT_766990000.gifSSFS_FFT_766990000_SSFSACp.txtSSFS_FFT_766990000_SSFSCorr.txtSSFS_FFT_766990000_zErrGCx30.txtSSFS_FFT_767040722_zErrGC_B1pACp.gifSSFS_JPC1.gifSSFS_JPC2.gifSSFS_RMS_765549800_RFCACp.txt
… careful analysis of 206 plots
19 Laser Frequency Stabilization – 2004, May 04
Experimental work (4)
Large transient at lock acquisition
20 Laser Frequency Stabilization – 2004, May 04
• Algo in Gc: start SSFS when correction signal is zero, and holds this zero => error signal is generally not null
=> excites the step response (large transient)
• NEW Algo in Gc to be implemented: start SSFS when error signal is null => then switch off the filter
=> decay slowly correction signal to zero
Experimental work (5)
Transient / algo in Gc
21 Laser Frequency Stabilization – 2004, May 04
• While working, we found in-loop resonances in the MC suspension at 18 Hz, 25 Hz, 53 Hz, 128 Hz, 333 Hz, …
• The reference mass is not holded by its wires, but by the coil wires! MC reference mass wires are not stresses and may
have random resonance frequencies, varying in time.
Experimental work (6)
MC SUSPENSION RESONANCES
22 Laser Frequency Stabilization – 2004, May 04
Noise performances
• 1 laser, 1 FP cavity, lock with high unity gain• error signal = readout noise• correction signal = beating note of laser cavity and FP cavity,
Usually dominated by laser cavity (« free running laser noise »)
• 1 laser locked on a FP cavity, lock of another cavity2nd cavity error signal = beating note of the 2 FP cavities
ex: experiment in Orsay in 95,ex: « ISYS »: IMC and reference cavity
• 1 laser, 3+ FP cavitiesex: « north arm » (C2)North arm, IMC, reference cavity
cf VIR-NOT-OCA-1390-260
23 Laser Frequency Stabilization – 2004, May 04
Noise performances
24 Laser Frequency Stabilization – 2004, May 04
Noise performances
25 Laser Frequency Stabilization – 2004, May 04
Next activities (1/2)
SSFS on north arm* update saturation in SSFS rack (+ RAMPEAUTO)* new algo in Gc (trigger condition)* check of IB-DSP/MC-DSP DOL* Gc: trigger=0 in the sequence* Gc: lock of RFC without intermediate steps* test Coulon’s filter (NI+NE)* increase of UG of SSFS* test with Virgo final corrector stage* SSFS -> ISYS reliability
SSFS on « recombined » interferometer* ready
Input MC control* TF measurement (again) (z,Tx,Ty)* control from 2 coils* change coil wires of MC suspension?
1-2 shifts1 shift
2 shifts1 shift4 shifts2-3 shifts
2-3 shifts½ shift???
(tentative durations)
26 Laser Frequency Stabilization – 2004, May 04
Next activities (2/2)
Lock of recycling cavity* improve rms of IMC length noise?* improve 50 Hz level on reference cavity* detune recycling cavity of 25 nm (1/10th linewidth)
SSFS on virgo
Noise and requirements* cabling of « pertub » input* calibration sequence
Simulation* Siesta simulation of SSFS(fs = 200 kHz, does not include IMC error signal saturation)
3-4 weeks2-3 shifts1 shift
2 weeks
1-2 weeks