March 12, 2022
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At 808 nm:
| angle (degrees) | Rp | Rs |
|---|---|---|
| 0 | 0.041365 | 0.041365 |
| 5 | 0.040948 | 0.041784 |
| 10 | 0.039693 | 0.043069 |
| 15 | 0.037593 | 0.045301 |
| 20 | 0.034640 | 0.048630 |
If angle of incidence is 10 degrees, reflected beam rotates by 20 degrees. If beam of diameter D rotates by theta, distance it must travel to not have incident and reflected overlap obeys tan(theta)=D/L so L/D=1/tan(theta)
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| Description | Qty | Part # | Details | Purchase Date |
|---|---|---|---|---|
| Ø2" UVFS Wedged Window, Uncoated | 8 | WW42012 | 8/8. | 01/30/24 |
| 60 mm Cage Cube | 8 | LC6WR | 8/8. | 01/30/24 |
| Light-Tight Blank Cover Plate for 60 mm Cage Cube, 1/4"-20 Tap | 10 | LB1C | 10/10. | 01/30/24 |
| SM2-Threaded Cover Plate for 60 mm Cage Cube | 4 | LB2C | 4/4. | 01/30/24 |
| Kinematic Prism Platform for 60 mm Cage Cube, Imperial Taps | 6 | LB4C | 6/6. | 01/30/24 |
| 60-mm-Cage-Compatible Rectangular Filter Mount | 2 | LFFM1 | 2/2. | 01/30/24 |
| Ø2" Optic Mount for 60 mm Cage Cube with Setscrew Optic Retention | 8 | LB5C1 | 8/8. | 01/30/24 |
| 60 mm Kinematic Cage Cube Connector | 8 | DFM2-CC | 8/8. | 01/30/24 |
| 6mm cage connector rods of various lengths | all received. | |||
| fast plano-convex lenses | various | all received. | ||
| optical shutter? Thorlabs | ||||
| optical chopper following monochromator | ||||
| condensing lens for photodiode | ||||
| order blocking filter, controller servo |
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Current status of the project is temporarily described in this document.
Some potential 25-30 degree Optical Wedges to purchase for sending light into our photodiode:
Near perfect angle, but small: DWG No. 47622
Alternative: 30-60-90 Littrow dispersion prism: DWG No. 43649 https://www.edmundoptics.com/f/30deg---60deg---90deg--littrow-dispersion-prisms/12453/
We're going with the first choice, the 25mm wedge prism from EO.
A condenser lens should go with it.
Condenser lenses EO list:
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May 15, 2024
We have an idea to improve our ability to redirect refracted light to a photodiode. We will use a wedge prism that has a wedge angle similar to the refraction angle of light through the glass, as governed by its index of refraction. As a result, the refracted light should travel down the length of the prism and exit normal to the opposite side of the prism, whose face is orthogonal to the long axis of the prism (not wedged). On this backside of the prism, we will graft on a condensing lens that should cleanly focus the light onto the photodiode. This results in more precise management and control over the light we will use for referencing to our photodiode.
Orders have been placed for:
x1 Optical wedge, the 15 deg. Nom. Uncoated, N-BK7 Wedge Prism.
x1 Condenser lens, 25mm Dia., 0.25 Numerical Aperture, Uncoated, Precision Aspheric Lens.
x1 2" clear aperture adapter, AD2-CA - Ø2" OD Adapter for Ø1" Optic with Clear Aperture, 0.28" Thick.
x1 2" to 1" center adapter, AD2 - Ø2" OD Adapter for Ø1" Optic, 0.25" Thick.
I was only able to find a 1" BK7 wedge (25.25 degrees) that fit the calculated refraction angle of BK7 / UVFS, which ranges from 26-28 degrees for BK7 and 27-29 degrees for UVFS over the range 0.2 - 1 micron.
Alternatively, we could probably use a 30-60-90 prism, but I was unable to find a size larger than 1" made of BK7/UVFS, that was available off-the-shelf.
Since one surface is now N-BK7, I have ordered a 2" N-BK7 plano-convex lens to accompany it to ensure we don't introduce fractional polarization asymmetrically.
Reference:
(Galvez, E. (2001). Achromatic polarization-preserving beam displacer. Optics Letters, 26(13), 971–973. https://doi.org/10.1364/OL.26.000971)
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