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Entry  Thu Aug 5 09:20:44 2021, Aidan, Laser, 2um Photodiodes, Optical design for 2um PD in new cryo chamber Cryo_Chamber_optical_layout.pdf
    Reply  Thu Aug 5 12:39:56 2021, Aidan, Laser, 2um Photodiodes, Optical design for 2um PD in new cryo chamber Cryo_in-air_setup.pdf
       Reply  Thu Aug 5 14:29:42 2021, Stephen, Laser, 2um Photodiodes, Optical design for 2um PD in new cryo chamber IMG_9685.JPGIMG_9687.JPGrouting_markup_of_IMG_9688.pngIMG_9682.JPG
          Reply  Tue Aug 24 15:01:25 2021, Stephen, Laser, 2um Photodiodes, 2um PD in new cryo chamber 
             Reply  Thu Aug 26 14:31:46 2021, Aidan, Stephen, Laser, 2um Photodiodes, Incident power calibration of 2um PD in new cryo chamber IMG_4420.jpgREF_PD_POW_CAL_cryo.pdf
                Reply  Fri Aug 27 17:57:30 2021, Stephen, DailyProgress, 2um Photodiodes, Start of PD pumpdown  
                   Reply  Sat Aug 28 07:01:21 2021, Aidan, DailyProgress, 2um Photodiodes, Start of PD pumpdown  20210828_-_IMG_4445.jpg20210828_-_IMG_4443.jpg
                      Reply  Sun Aug 29 11:17:43 2021, Aidan, DailyProgress, 2um Photodiodes, Start of PD pumpdown  Screen_Shot_2021-08-29_at_11.16.55_AM.pngScreen_Shot_2021-08-29_at_11.22.03_AM.png
                         Reply  Mon Aug 30 08:04:52 2021, Aidan, DailyProgress, 2um Photodiodes, Monday morning observation of JPL A1 PD cool down  Screen_Shot_2021-08-30_at_8.04.15_AM.png
Message ID: 2637     Entry time: Thu Aug 5 12:39:56 2021     In reply to: 2635     Reply to this: 2639
Author: Aidan 
Type: Laser 
Category: 2um Photodiodes 
Subject: Optical design for 2um PD in new cryo chamber 

Here's a more detailed layout of the in-air design for the PD testing. Things to note:

  1. I've changed the telescope to a ~1:2 beam expander using a 40mm lens and a 75mm lens. This allows for greater tuning of the beam size on the PD
  2. I added the picomotor mirror for fine-tuning of the beam steering onto the PD (I have to check how much control this translates to on the PD inside the vacuum system).
  3. The picomotor mirror is open loop, so there is a QPD to monitor the actual pointing of the mirror
Quote:

I've sketched out a way to change the beam size on the in-vacuum PD. I think the beam diameter coming from the collimator is 1.2mm, but I need to check this. If we add a telescope outside the vacuum system and put the second lens of this on a translation stage, then this provides us with wide control of the beam size on the PD inside the vacuum system (about 400mm away).

 

 

 

 

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