Differences between revisions 1 and 24 (spanning 23 versions)

Balanced Homodyne Detection

Requirements

Displacement noise of OMC/LMC mirrors
1. Are we using a single cavity or two?
Scatter loss in mirrors
1. This will affect the backscatter into the IFO
2. This will limit the transmissivity of the cavity for a given finesse.
Cavity design: triangle, quad ring, quad zig-zag (reference the new OMC paper from Koji)
1. What does this mean?
Laser amplitude / frequency noise including DC offsets in various other lock points and motions to simulate bilinear noise
Oscillator noise: AM / FM
1. This will set the requirement on the filtering necessary.
Aux length noise: MICH/PRC/ SRC
Req. on offsets/asymmetries: arm finesse, arm reflectivity, mass imbalance of ETMs
Phase noise of LO
1. This will set the requirement on whatever we use to control the homodyne angle.
Polarization stability requirement for polarization BHD
1. i.e. let's say we have some finite Ip/Is ratio. What does this mean for the readout in signal-referred units?
Backscatter
1. RIN on the LO
2. Phase noise due to motion of the mirrors

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.

-  ⇤ ← Revision 1 as of 2017-10-27 04:47:55 → 
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  Editor: RanaadhikariATligoDOTorg
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+   ← Revision 24 as of 2019-05-10 05:59:40 → ⇥
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  Editor: GautamvenugopalanATligoDOTorg
  Comment:
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-OMG Kevin put some stuff here.
+= Balanced Homodyne Detection =


==== Requirements ====
 1. Displacement noise of OMC/LMC mirrors
    1. Are we using a single cavity or two?
 1. Scatter loss in mirrors
    1. This will affect the backscatter into the IFO
    1. 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)
    1. 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
    1. 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
    1. This will set the requirement on whatever we use to control the homodyne angle.
 1. Polarization stability requirement for polarization BHD
    1. 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
    1. RIN on the LO
    1. Phase noise due to motion of the mirrors

==== 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]]