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= Green Laser Injection for Arm Pre-Lock = = Arm Length Stabilization by injecting green laser beams from the arm ends =
<<TableOfContents([2])>>aLIGO ALS wiki
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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. http://ilog.ligo-wa.caltech.edu:7285/advligo/Arm_Length_Stabilisation
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== Basic Concept == -------
-------
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== 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 ?		 == Plan ==
=== time line ===
 * [[Upgrade 09/GreenLock/timeline|time line]] describes where we are now and where we go.
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=== 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.
However, the common motion of the cavity mirrors will not be suppressed. This common motion will show up as phase noises of the lasers. The time derivative of phase noise is equivalent to frequency noise. The equivalent displacement noise seen 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, L is the length of the cavity and c is the speed of light (see [attachment:PhaseNoise.pdf|this]).
=== Conceptual design ===
 * Description of the optical / servo configuration [https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=6888 LIGO DCC]
 * Servo modeling (!SimLink) [https://nodus.ligo.caltech.edu:30889/svn/trunk/docs/upgrade08/Green_Locking/Servo_modeling/ 40mSVN]

=== Detailed design ===
 * '''Design and Purchasing Lists'''
  * Optical design / [[Upgrade 09/Purchase List/Green Locking|item list]]
  * Electronics / control design / [[Upgrade 09/Purchase List/Green Locking|item list]]
  * [[Upgrade 09/Purchase List/Green Locking|Purchase list]]
 * '''Detailed considerations'''
  * Optical Layout ([attachment:green_optics.png Table]/ In-vac)
   * [[Upgrade 09/GreenLock/end table|ETM / end table]] <<ImageLink(endtable.jpg,Upgrade 09/GreenLock/end_table)>>
   * [[Upgrade 09/Optical Layout#wedge|ITM wedge effect]]
   * [[Upgrade 09/Optical Layout|Periscopes for beam steering from PR3/SR3 transmissions to the PSL viewport]]
   * PSL viewport modification (viewport cover / tube / PSL box / periscope on the PSL table)
   * PSL table
   * Laser & SHG specs --- power, polarization, Xtals
    . '' - references''
    . [1] G.D.Boyd and D.A. Kleinman, [http://jap.aip.org/japiau/v39/i8/p3597_s1 "Parametric interaction of Focused Gaussian Light Beams", J.A. Phys. 39, 3597 (1968)]

    . [2] C. Zhang, Y.Qin and Y.Zhu, [http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-33-7-720 "Perfect quasi-phase matching for the third-harmonic generation using focused Gaussian beams",Opt. Lett. 33, 720 (2008)]

  * Main optics specs (review)
  * Mode matching ([attachment:modematch_END.png mode matching at end table])
  * Green generation
   . [attachment:manual_oven.pdf manual for the covesion oven]
  * Expected performance / noise / control system range
  * Digital servo / operation
  * Alignment (initial / fine / automatic)

==== Green Preliminary Design: ETM region ====
attachment:green_ETM_preliminary_design.png

==== Green Preliminary Design: Vertex region ====
attachment:green_vertex_preliminary_design.png

=== Development roadmap ===
 * '''End table arrangement'''
  * NPRO placement / optical assembly at the end

  * SHG at the end table
  * Control system placement
  * Coarse alignment to the cavity
  * Fine alignment
  * Lock of the green beam to the cavity
 * '''At the PSL table'''
  * SHG at the PSL table
 * '''Digital control'''
  * Virtual Green lock by RCG
  * GPIB interfaces
 * '''Vertex tank optical arrangement'''
  * In-vac steering (PO transmission / Periscope / Mirrors)
  * Vertex phase noise measurement
   * Electronics placement
   * Control system implementation
 * '''Performance evaluation'''
  * f_noise of green beam / PDH performance

  * Relative f_noise between the PSL green and the Arm transmitted green
  * ALS performance
 * '''Sophistication of the scheme'''
  * Automatic handing off scripts

  * Ready-to-go panels for AdvLIGO
  * Automatic alignment of the green beam
  * ---
  * Green Michelson for precise ETM calibration

  * Absolute length / mode spacing measurement by green''' '''

----
== Control information ==
=== Laser Frequency vs Crystal Temperature ===
Plots of the laser frequency vs temperature (measured by beating against a second laser) are shown below. [http://nodus.ligo.caltech.edu:8080/40m/2794 Also, see the elog here].

|| '''Laser''' || '''df/dT''' || '''df/dV - within a mode''' || '''df/dV - average''' ||
|| Lightwave || 2.8MHz/mK || 5GHz/V || 1.6GHz/V ||
|| Innolight || 3.3MHz/mK || || ||


==== Lightwave laser ====
attachment:lightwave_temperature_sweep.png

==== Innolight laser ====
attachment:innolight_temperature_sweep.png

= Noise Requirements =
[[Upgrade 09/GreenLock/Noise Requirement|jump to Noise Requirement]]

Arm Length Stabilization by injecting green laser beams from the arm ends

<<TableOfContents: execution failed [Argument "maxdepth" must be an integer value, not "[2]"] (see also the log)>>aLIGO ALS wiki

http://ilog.ligo-wa.caltech.edu:7285/advligo/Arm_Length_Stabilisation

Plan

time line

  • time line describes where we are now and where we go.

Conceptual design

Detailed design

Green Preliminary Design: ETM region

attachment:green_ETM_preliminary_design.png

Green Preliminary Design: Vertex region

attachment:green_vertex_preliminary_design.png

Development roadmap

  • End table arrangement

    • NPRO placement / optical assembly at the end
    • SHG at the end table
    • Control system placement
    • Coarse alignment to the cavity
    • Fine alignment
    • Lock of the green beam to the cavity

  • At the PSL table

    • SHG at the PSL table

  • Digital control

    • Virtual Green lock by RCG
    • GPIB interfaces

  • Vertex tank optical arrangement

    • In-vac steering (PO transmission / Periscope / Mirrors)
    • Vertex phase noise measurement
      • Electronics placement
      • Control system implementation

  • Performance evaluation

    • f_noise of green beam / PDH performance
    • Relative f_noise between the PSL green and the Arm transmitted green
    • ALS performance

  • Sophistication of the scheme

    • Automatic handing off scripts
    • Ready-to-go panels for AdvLIGO
    • Automatic alignment of the green beam
    • ---
    • Green Michelson for precise ETM calibration

    • Absolute length / mode spacing measurement by green

Control information

Laser Frequency vs Crystal Temperature

Plots of the laser frequency vs temperature (measured by beating against a second laser) are shown below. [http://nodus.ligo.caltech.edu:8080/40m/2794 Also, see the elog here].

Laser

df/dT

df/dV - within a mode

df/dV - average

Lightwave

2.8MHz/mK

5GHz/V

1.6GHz/V

Innolight

3.3MHz/mK

Lightwave laser

attachment:lightwave_temperature_sweep.png

Innolight laser

attachment:innolight_temperature_sweep.png

Noise Requirements

jump to Noise Requirement

Advanced_Techniques/Green_Locking (last edited 2015-06-23 03:44:00 by EricquinteroATligoDOTorg)