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Message ID: 10410     Entry time: Tue Aug 19 21:40:44 2014
Author: Andres 
Type: Update 
Category: IMC 
Subject: New Optical Setup for the IMC 

IMC Calculation and Setup

I have been working in the calculation for improving the Gouy Phase separation between the WFSs. I tried different possible setup, but the three big constrains in choosing a good optical table setup are to have a Waist size that range from 1mm-2mm, the Gouy Phase  between the WFSs have to be greater than 75 degrees and there has to be a steering mirror before each WFS. I will be showing the best calculation because that calculation complies with Rana request of having both WFSs facing west and having the shortest beam path. I approximate the distances by measuring with a tape the distance where the current optics are located and by looking at the picture that I took I approximated the distance where the lenses will be placed. I'm using a la mode for calculating the gouy phase different. I attached a picture of the current optical table setup that we have. Using a la mode, I found that the current gouy phase that we have is 49.6750 degrees.

Now, for the new setup, a run a la mode and found a Gouy phase of 89.3728 degrees. I have to create a two independent beam path: one for the WFS1 and another one for WFS2. The reason for this is that a la mode place everything in one dimension so and since the WFS1 will have a divergence lens in order to increase the waist size, and since that lens should not be interacting with the waist size in the WFS2. We need two beam path for each WFS.  A la mode give us the following solution:

For the beam path of the WFS1

    label                z (m)           type             parameters        
    -----                  -----              ----             ----------        
    MC1                   0              flat mirror          none:           
    MC3                   0.1753     flat mirror          none:           
    MC2                   13.4587   curved mirror    ROC: 17.8700 (m)     
    Lens1                 29.3705   lens                  focalLength: 1.0201 (m)
    BS2                    29.9475   flat mirror          none:           
    First Mirror         30.0237   flat mirror          none:           
    Lens3                30.2000    lens                  focalLength: -0.100 (m)
    WFS1                30.4809    flat mirror         none: 

For the beam path of the WFS2

    label                   z (m)             type             parameters        
    -----                    -----                 ----             ----------        
    MC1                    0               flat mirror          none:           
    MC3                    0.1753      flat mirror          none:           
    MC2                    13.4587    curved mirror    ROC: 17.8700 (m)     
    Lens1                  29.3705    lens                   focalLength: 1.0201 (m)
    BS2                     29.9475    flat mirror          none:           
    Second Mirror    30.2650     flat mirror          none:           
    Lens2                 30.4809     lens                  focalLength: -0.075 (m)
    Third Mirror        30.5698     flat mirror          none:           
    WFS2                30.6968      flat mirror          none:  

I attached bellow how the new setup should look like in the second picture and also I include and attachment of the a la mode code.

 I used Mist to be able to see the read out that we get in the WFSs that take the Mode Cleaner Reflection and the QPD that take the transmitted from MC2. In the following, plots I'm misaligned the each mirrors: MC1, MC2 and MC3. The misalignment are in Yaw and Pitch. I'm dividing the WFSs reading by the total power reflect power, and I'm dividing the QPD for the MC2 transmission by the total transmitted power. In my Mist model, I have a laser of 1W and my EOM is modulated at 30MHz instead of 29.5MHz and the modulation depth was calculating by measuring the applied voltage using and Spectrum analyzer. I using Kiwamu measurement of modulation depth efficiency vs the applied voltage, https://dcc.ligo.org/DocDB/0010/G1000297/001/G1000297-v1.pdf,  I got a modulation depth of 0.6 mrad. I put this modulation depth and I got the following plots: The fourth and fifth attachment are for the current optical setup that we have. The sixth and seventh attachment is for the new optical setup. The eighth attachment is showing the mode cleaner cavity resonating. The last attachment contains the plots of WFS1 vs WFS2, MC2_QPD vs WFS1, MC2_QPD vs WFS3 for each mirror misaligned. The last two attachment are the MIST code for the calculation.

We have all the lenses that we need. I checked it last Friday and if everything is good we will be ready to do the new upgrade this coming Friday. For increasing the power, I check and we have different BS so we can just switch from the current setup the BS. Can you let me know if this setup look good or if I need to chance the setup? I would really love to do this upgrade before I leave.

 

 

 

 

 

 

Attachment 1: ModeCleanerSetup.PNG  20.106 MB  Uploaded Tue Aug 19 14:08:07 2014  | Hide | Hide all
ModeCleanerSetup.PNG
Attachment 2: NewOpticalTableSetupForTheModeCleaner.PNG  20.195 MB  | Hide | Hide all
NewOpticalTableSetupForTheModeCleaner.PNG
Attachment 3: ReduceWFSPathWorkingOn.m.zip  1 kB
Attachment 4: MIST_WFSsAndQPDReadingForYaw.png  27 kB  | Hide | Hide all
MIST_WFSsAndQPDReadingForYaw.png
Attachment 5: MIST_WFSsAndQPDReadingForPitch.png  23 kB  | Hide | Hide all
MIST_WFSsAndQPDReadingForPitch.png
Attachment 6: MIST_WFSsAndQPDReadingForYawNewSetup.png  22 kB  | Hide | Hide all
MIST_WFSsAndQPDReadingForYawNewSetup.png
Attachment 7: MIST_WFSsAndQPDReadingForPitchNewSetup.png  24 kB  | Hide | Hide all
MIST_WFSsAndQPDReadingForPitchNewSetup.png
Attachment 8: MISTResonanceCavityReflectionAndTransmissionNewSetup.png  16 kB  | Hide | Hide all
MISTResonanceCavityReflectionAndTransmissionNewSetup.png
Attachment 9: 2Dplots.zip  168 kB
Attachment 10: ModeCleanerCurrentOpticalTableMIST.zip  3 kB
Attachment 11: ModeCleanerNewSetupMIST.zip  3 kB
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