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OMG Kevin put some stuff here. = Balanced Homodyne Detection =


==== Requirements ====
 1. Displacement noise of OMC/LMC mirrors
    * Are we using a single cavity or two?
 1. Scatter loss in mirrors
    * This will affect the backscatter into the IFO
    * This will limit the transmissivity of the cavity for a given finesse.
 1. Cavity design: triangle, quad ring, quad zig-zag (reference the new OMC paper from Koji)
    * What does this mean?
 1. Laser amplitude / frequency noise including DC offsets in various other lock points and motions to simulate bilinear noise
 1. Oscillator noise: AM / FM
    * This will set the requirement on the filtering necessary.
 1. Aux length noise: MICH/PRC/ SRC
 1. Req. on offsets/asymmetries: arm finesse, arm reflectivity, mass imbalance of ETMs
 1. Phase noise of LO
    * This will set the requirement on whatever we use to control the homodyne angle.
 1. Polarization stability requirement for polarization BHD
    * i.e. let's say we have some finite Ip/Is ratio. What does this mean for the readout in signal-referred units?
 1. Backscatter
    * RIN on the LO
    * Phase noise due to motion of the mirrors
 1. Pointing
    * If we opt to not use a mode-cleaner for the LO field, what is the pointing requirement on whatever option we choose?
 1. Suspension
    * What kind of suspension(s) are we planning to use?
    * [[https://dcc.ligo.org/DocDB/0121/D1500274/004/D1500274-v4 aLIGO VOPO Base Plate.PDF|VOPO]] and [[https://dcc.ligo.org/DocDB/0000/D0900308/004/D0900308-v4_aLIGO_OMC_Structural Weldment.PDF|OMCS]] seem too big to fit on any of our existing tables.
 1. Control scheme
    * How will we control the LO phase?

==== Action items ====
 * Design SRC so that
  1. Suppress 02/20 modes
  1. Partially transmit 01/10 modes for AS WFS
  1. Suppress thermally generated modes
  1. After the above have been satisfied, choose transmission to maximize ponderomotive squeezing
 * Budget above noises, but especially investigate polarization stability.
 * How is homodyne angle controlled?
 * Beam routing
  * Where to pick off LO?
  * Can we use ETMX transmission for LO? (Koji is crazy)
 * A+ BHD noise budget for both baseline double OMC and polarization BHD.
 * Can we add a heater back to OMC mirror to control ROC? How should the temperature be sensed and controlled?
  * Heater below breadboard for cavity length control
  * Heater on back of mirror for [[Balanced Homodyne Detection/RoC_control|RoC Control]]
  * Offload PZT DC voltage to slow servo (breadboard heater) to always keep PZT in the middle of the range

==== Modeling/Noise Budget ====
 * Some BHD modeling is done in the OptimalGWextraction repo [[https://github.com/CaltechExperimentalGravity/OptimalGWextraction/tree/master/PonderSqueeze/BHD|here]].

==== Polarization BHD ====
 * [[https://dcc.ligo.org/LIGO-G1802013|Some thoughts on polarization BHD (LIGO-G1802013)]]
 * [[attachment:OMC.pdf|Polarization BHD notes]]

==== Other Links ====
 * [[https://wiki.ligo.org/AIC/BHD_A_plus|A+ BHD wiki]]
 * [[https://wiki.ligo.org/AIC/BHD_MIT_WS|MIT A+ BHD workshop wiki]]

Balanced Homodyne Detection

Requirements

  1. Displacement noise of OMC/LMC mirrors
    • Are we using a single cavity or two?
  2. Scatter loss in mirrors
    • This will affect the backscatter into the IFO
    • This will limit the transmissivity of the cavity for a given finesse.
  3. Cavity design: triangle, quad ring, quad zig-zag (reference the new OMC paper from Koji)
    • What does this mean?
  4. Laser amplitude / frequency noise including DC offsets in various other lock points and motions to simulate bilinear noise
  5. Oscillator noise: AM / FM
    • This will set the requirement on the filtering necessary.
  6. Aux length noise: MICH/PRC/ SRC
  7. Req. on offsets/asymmetries: arm finesse, arm reflectivity, mass imbalance of ETMs
  8. Phase noise of LO
    • This will set the requirement on whatever we use to control the homodyne angle.
  9. Polarization stability requirement for polarization BHD
    • i.e. let's say we have some finite Ip/Is ratio. What does this mean for the readout in signal-referred units?
  10. Backscatter
    • RIN on the LO
    • Phase noise due to motion of the mirrors
  11. Pointing
    • If we opt to not use a mode-cleaner for the LO field, what is the pointing requirement on whatever option we choose?
  12. Suspension
    • What kind of suspension(s) are we planning to use?

    • VOPO and OMCS seem too big to fit on any of our existing tables.

  13. Control scheme
    • How will we control the LO phase?

Action items

  • Design SRC so that
    1. Suppress 02/20 modes
    2. Partially transmit 01/10 modes for AS WFS
    3. Suppress thermally generated modes
    4. After the above have been satisfied, choose transmission to maximize ponderomotive squeezing
  • Budget above noises, but especially investigate polarization stability.
  • How is homodyne angle controlled?
  • Beam routing
    • Where to pick off LO?
    • Can we use ETMX transmission for LO? (Koji is crazy)
  • A+ BHD noise budget for both baseline double OMC and polarization BHD.
  • Can we add a heater back to OMC mirror to control ROC? How should the temperature be sensed and controlled?
    • Heater below breadboard for cavity length control

    • Heater on back of mirror for RoC Control

    • Offload PZT DC voltage to slow servo (breadboard heater) to always keep PZT in the middle of the range

Modeling/Noise Budget

  • Some BHD modeling is done in the OptimalGWextraction repo here.

Polarization BHD

Balanced Homodyne Detection (last edited 2020-04-29 17:41:39 by JonathanrichardsonATligoDOTorg)