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Entry  Tue Jul 1 19:27:25 2014, tara, DailyProgress, Computers, Installing prosilica gc750 
    Reply  Tue Jul 15 18:26:20 2014, tara, DailyProgress, optic, setting up scattered light measurement photo.JPG
       Reply  Thu Jul 17 18:57:54 2014, tara, DailyProgress, optic, setting up scattered light measurement dark1.pnglight.pngresidual.pngscattered_.zip
          Reply  Wed Jul 23 00:28:14 2014, tara, DailyProgress, optic, setting up scattered light measurement exp_vs_light.pngpower.png
             Reply  Thu Jul 24 02:00:23 2014, tara, DailyProgress, optic, setting up scattered light measurement power.pngphoto-1.JPGphoto-2.JPG
Message ID: 1456     Entry time: Thu Jul 24 02:00:23 2014     In reply to: 1455
Author: tara 
Type: DailyProgress 
Category: optic 
Subject: setting up scattered light measurement 

I rechecked the CCD response vs exposure time and power. The results are linear.


After some adjustments (strain relief on the camera's cables, clamping down the camera properly), I made sure that the camera is more stable and repeated the measurement. The CCD response is linear with the incident power on the sample (this is under the assumption that the scattered power is directly proportional to the incident power). 


Fig1:  CCD response vs incident power. The camera response is linear.

== AlGaAs Samples==

I prepared the sample for measurements. All the samples are quite dirty, especially on the flat sides. So I wiped all of them. I still cannot get rid off some water marks on the annulus of the mirror. It might cause some problems when I optical contact the mirrors. I'll try to clean them later.


fig2: one of the AlGaAs mirrors before cleaning. 

I put one of the samples in the scattered light setup. The transmitted beam has a lot of diffused light behind the mirror. The amount of the diffused light changes with the beam direction. I'm not sure exactly why. I'll try to investigate it more. But the scattered light from the sample is very small. Most of the light is from debris on the surface, not the micro roughness of the sample. The amount of scattered light significantly changes with the beam position on the mirror.


fig3: diffused light behind the mirror. It might come from the reflection inside the substrate because the incident beam is not normal to the surface.

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