Overview

The diagrams below show a conceptual design of the green locking technique

Plans

long term plans	action item list	[:Advanced_Techniques/Green_Locking/action_item_list]
past plans	October 2010	[:Advanced_Techniques/Green_Locking/October_2010]
	November 2010	[:Advanced_Techniques/Green_Locking/November_2010]
	January 2011	[:Advanced_Techniques/Green_Locking/January_2011]

Developer's page

Category	Links
Optical Layout	[attachment:green_optics.png Table] / In-vac
end table	Picture of ETMY table / Picture of ETMX table
Lasers	Lasers (specs, temp settings, etc.)
Optics	ITM wedge effect / Mirror RT measurement
Mode matching	([attachment:modematch_END.png mode matching at end table])
Electronics	[:Advanced_Techniques/Green_Locking/Electronics]
SHG	[:Advanced_Techniques/Green_Locking/SHG]
Doubling Oven	[attachment:PV40.pdf drawing of PV40 oven], [attachment:PVP2.pdf drawing of the base plate PVP2], [attachment:manual_oven.pdf manual for the covesion oven]
Performance	Noise Requirement
Purchase list	[:Upgrade 09/Purchase List/Green Locking]

Links

aLIGO ALS wiki	http://ilog.ligo-wa.caltech.edu:7285/advligo/Arm_Length_Stabilisation
Servo modeling (SimLink)	https://nodus.ligo.caltech.edu:30889/svn/trunk/docs/upgrade08/Green_Locking/Servo_modeling/

Documents

Title	Locations
Description of the optical / servo configuration	https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=6888
Arm Length Stabilization at the 40m prototype	[https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=39965 G1100301-v1]

-  ⇤ ← Revision 9 as of 2009-08-25 10:20:50 → 
  Size: 2727
  Editor: YoichiAso
  Comment:
+   ← Revision 142 as of 2011-09-23 06:23:44 → ⇥
  Size: 2521
  Editor: KiwamuIzumi
  Comment:
-Deletions are marked like this.
+Additions are marked like this.
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-= Green Laser Injection for Arm Pre-Lock =
+## page was renamed from Upgrade 09/GreenLock
<<Anchor(TOP)>>
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+Line 4:
-We plan to install green lasers, which are phase locked to the PSL laser, at each end station to pre-lock the arm cavities before the lock acquisition.
+   . attachment:god_of_green.png
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+Line 7:
-== Basic Concept ==
-Line 7:
+Line 8:
-== Noise Requirement ==
I'd say the arm cavity length should not change more than 1/100 of the resonance width in the time scale of 10sec.[[BR]]
For this to be fulfilled, the RMS fluctuation of the cavity length must be suppressed below 1e-11m level.[[BR]]
Does this make sense ?
-Line 12:
+Line 9:
-=== Noise Sources ===
==== PLL phase noise ====
==== Phase noise from the cavity common mode motion ====
When the cavity is locked to the green laser, the differential motion of the two mirrors will be suppressed by the servo.[[BR]]
However, the common motion of the cavity mirrors will not be suppressed. This common motion will show up as phase noises [[BR]]
of the lasers. The time derivative of phase noise is equivalent to frequency noise. The equivalent displacement noise seen [[BR]]
by the cavity is dL=(w*x*L)/c, where w is the angular frequency, x is the displacement noise spectrum of the common motion, [[BR]]
L is the length of the cavity and c is the speed of light (see [attachment:PhaseNoise.pdf] for derivation).
-Line 21:
+Line 10:
-attachment:Cavity-Common-Diff.png
+= Overview =
-Line 23:
+Line 12:
-The two lasers (PSL and green) see the same motion of the cavity but from the opposite sides. Hence, the effect of this phase [[BR]]
noise to the two error signals of the green and the PSL lasers will be 180 deg. out of phase. The feedback from the green laser to [[BR]]
the cavity length will, therefore, create a noise for the PSL laser.
+ The diagrams below show a conceptual design of the green locking technique
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+Line 14:
-In order to estimate the contribution of this noise to the green lock, I plotted the estimated phase noise in the following figure.[[BR]] 
attachment:PhaseNoise.png
+   <<ImageLink(green_vertex_preliminary_design.png,Upgrade 09/GreenLock/Preliminary design for the vertex,height=200)>>
   <<ImageLink(green_ETM_preliminary_design.png,Upgrade 09/GreenLock/Preliminary design for the end,height=200)>>
-Line 30:
+Line 17:
-I first took a spectrum of ETMX OSEM pos signal to see the motion of the mirror with damping.[[BR]]
The blue curve in the figure shows the calibrated OSEM spectrum using the well known 2V/mm OSEM [[BR]]
calibration and the whitening filter shape (3Hz zero, 30Hz and 100Hz pole).[[BR]]
However, OSEM signal is not a good measure of the seismic noise below the pendulum resonant frequency[[BR]]
because the suspension cage and the mirror move together at low frequencies.[[BR]]
As a tentative solution, I put a filter to make the spectrum look like 1/f^2 below 0.8Hz.[[BR]]
This is diffinitely a hacky solution, and should be replaced with a correctly measured [[BR]]
seismic spectrum.
+= Plans =
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+Line 19:
-The estimated seismic motion was converted to the phase noise using the above formula.[[BR]]
The RMS displacement noise above 0.1Hz is about 3e-12 m, which satisfies the requirement for [[BR]]
the green lock stability (1e-11m).
+|| ''' long term plans ''' || ''' action item list ''' ||  [:Advanced_Techniques/Green_Locking/action_item_list] ||
||<|3> ''' past plans ''' ||''' October 2010''' || [:Advanced_Techniques/Green_Locking/October_2010] ||
|| ''' November 2010 '''||[:Advanced_Techniques/Green_Locking/November_2010] ||
||'''January 2011''' || [:Advanced_Techniques/Green_Locking/January_2011] ||
[[BR]]

= Developer's page =
||<:> ''''' Category ''''' ||<:> ''''' Links ''''' ||
||''' Optical Layout '''|| [attachment:green_optics.png Table]  /   [[Optical_Layout|In-vac]] ||
|| ''' end table ''' || [[ETMY_table|Picture of ETMY table]] / [[ETMX_table|Picture of ETMX table]]||
|| ''' Lasers ''' || [[Advanced_Techniques/Green_Locking/Lasers|Lasers (specs, temp settings, etc.)]] ||
|| ''' Optics ''' ||  [[Optical Layout#wedge|ITM wedge effect]] /  [[Upgrade_09/Optics/RTmeasurement|Mirror RT measurement]]||
|| '''  Mode matching ''' || ([attachment:modematch_END.png mode matching at end table]) ||
|| ''' Electronics ''' || [:Advanced_Techniques/Green_Locking/Electronics]||
|| ''' SHG ''' || [:Advanced_Techniques/Green_Locking/SHG] ||
|| ''' Doubling Oven ''' ||  [attachment:PV40.pdf drawing of PV40 oven], [attachment:PVP2.pdf drawing of the base plate PVP2],  [attachment:manual_oven.pdf manual for the covesion oven] ||
|| ''' Performance ''' ||[[Advanced_Techniques/Green_Locking/Noise Requirement|Noise Requirement]] ||
|| ''' Purchase list ''' ||  [:Upgrade 09/Purchase List/Green Locking] ||


= Links =
|| ''' aLIGO ALS wiki ''' || http://ilog.ligo-wa.caltech.edu:7285/advligo/Arm_Length_Stabilisation ||
|| ''' Servo modeling (!SimLink) ''' || https://nodus.ligo.caltech.edu:30889/svn/trunk/docs/upgrade08/Green_Locking/Servo_modeling/ ||

= Documents =
||<:> ''''' Title ''''' ||<:> ''''' Locations ''''' ||
|| ''' Description of the optical / servo configuration ''' || https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=6888  ||
|| ''' Arm Length Stabilization at the 40m prototype ''' || [https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=39965 G1100301-v1]||