Page for my timeline & development of RACBP.
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 |
| Thorlabs Cage Assembly Rods of various lengths from 1" to 8". | various | ER1-ER8, various | all received. | Feb 29 |
| Fast UVFS plano-convex lenses | various | various | all received. | Mid-March |
| Spectral Products Digikrom CM110/112 Monochromator | 2 | CM110/112 | received. | Mid-April |
Status updates:
An initial version of the RACBP was constructed in the benchtop lab setup on Feb. 22.
Initial testing with a 532nm laser unfortunately showed strong and tightly spatially located double-bounce propagation through the system, indicating that the 30-arcmin wedge on the wedge windows purchase would be insufficient for canceling double-bounce issues.
Consequently, plano-convex lenses of the fastest f-ratio were ordered and installed the following week as replacements to the wedge windows; initial observation reveal that this modification appears to successfully cancel out double bounces, representing a step closer to taking controlled flux measurements through the system at this proof-of-concept stage.
An overview of the project is described in this document, and also our modeling goals.
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.