March 12, 2022
While successful, implementation of collimated beam projector to date has two issues: 1) dynamic range mismatch between monitor diode (wants nA of current) and astronomical instrument (100,000 electrons per pixel max), and 2) not directly monitoring beam at exit pupil, due to size mismatch.
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From https://refractiveindex.info/?shelf=glass&book=BK7&page=SCHOTT
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)
| theta_incidence | theta_refl | L/D |
|---|---|---|
| 5 | 10 | 5.7 |
| 10 | 20 | 2.7 |
| 15 | 30 | 1.7 |
Purchases
Lambda optics 2 inch concave mirror blanks, polished both sides.
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Using https://lightmachinery.com/optical-design-center/more-optical-design-tools/prism-designer/
| apex angle | incidence angle | 300 nm angle | 1100 nm angle | difference |
|---|---|---|---|---|
| 1 | 1 | 0.487 | 0.449 | 2.2 arcmin |
| 1 | 10 | 0.4981 | 0.4589 | 2.35 arcmin |
| 10 | 5 | 4.904 | 4.523 | 22.86 arcmin |
This wedge pair needs to be tilted relative to incident beam. Five degree wedge angle seems good, as a pair. That gives us variation from zero to around 30 arcmin. For any sensible focal plane array of 4K x 4K
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RACBP Spring 2024 Parts List:
| 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 |
We note the reflective designs in this paper which document a 4-element system that adequately* preserves the initial polarization / phase of light.
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Reworking physical layout and installing double monochromator system and operation with expanded beam profile.
Kane To-Do:
polarization state output as fxn of angle of incidence for BK-7 and Fused Silica ... quantitative calcns sol'n: circular polarization?
python script to compute aggregate throughput
incidence / reflection angle tables / program
n(lambda) – check
labjack with mac mini
(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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