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Entry  Sun Jul 27 19:46:16 2014, Evan, DailyProgress, optic, BRDF of AlGaAs mirror 137B1 ccdImage.pdf137brdf.pdf
    Reply  Tue Jul 29 11:40:09 2014, Evan, DailyProgress, optic, BRDF of AlGaAs mirror 143 143brdf.pdf
       Reply  Wed Jul 30 17:47:56 2014, tara, DailyProgress, optic, BRDF of AlGaAs mirror 143 
Message ID: 1460     Entry time: Sun Jul 27 19:46:16 2014     Reply to this: 1461
Author: Evan 
Type: DailyProgress 
Category: optic 
Subject: BRDF of AlGaAs mirror 137B1 

[Tara, Evan]

We replaced the Lambertian diffuser with AlGaAs mirror 137B1. We intentionally induced a nonzero AOI of the incident beam, so that the reflected beam could be dumped cleanly. At a distance of 25.7(3) cm back from the mirror, the reflected and incident beams were separated by 1.3(1) cm, giving an AOI of 1.45(11)°.

  1. We measured the incident laser power as 9.94(2) mW.
  2. We set the exposure time of the camera to 250 ms.
  3. We swung the boom to 13°, 16°, 19°, 22°, 25°, 28°, 31°, and 34°. At each angle, we took 5 CCD images with the beam incident, and 1 CCD image with the beam blocked.
  4. We measured the incident laser power as 9.95(2) mW.
  5. Because the scattered power had fallen off sharply by 30°, we turned up the exposure time to 1.00 s.
  6. We swung the boom to 31°, 34°, 37°, 40°, and 43°. At each angle, we took 5 CCD images with the beam incident, and 1 CCD image with the beam blocked.
  7. We measured the incident laser power as 10.08(2) mW.
  8. We swung the boom to 46°, 49°, 52°, 55°, 58°, 61°, 64°, 67°, and 70°. At each angle, we took 5 CCD images with the beam incident, and 1 CCD image with the beam blocked.
  9. We measured the incident laser power as 10.06(2) mW.

For all of these measurements, the two ND filters (OD1.5+OD3.0) were not attached; just the RG1000. With the ThorLabs power meter, we measured the combined transmissivity of these two ND filters to be 1865(14) ppm.

The first attachment shows an example CCD image. The second attachment shows the raw counts, the inferred scattered power, and the BRDF.

Attachment 1: ccdImage.pdf  811 kB  Uploaded Sun Jul 27 22:27:03 2014  | Hide | Hide all
ccdImage.pdf
Attachment 2: 137brdf.pdf  750 kB  Uploaded Mon Jul 28 16:00:11 2014  | Hide | Hide all
137brdf.pdf
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