Beam Splitters: Cube, Plate, or Pellicle

On: Mon, Aug 06, 01 04:40:49 PM

Brian wrote:

I'm replacing my old plate beam splitters with something better, either cubes or pellicles. The pellicles seem to be cheaper than the cubes, and are easier to find in different ratios. However, I'm worried about the stability of the pellicles since they're essentially miniature drums with a tight skin. Seems that they could be prone to vibrations from any ambient sound in the room. So, can anyone recommend or not the use of pellicles? Also, can you recommend a good source for inexpensive cube beam splitters? -Brian
RESPONSES

Frank DeFreitas - Mon, Aug 27, 01 10:28:27 PM

Remember that you have primary and secondary reflections coming off of any beamsplitter. In holography, they have to have enough "split" between them -- so you can utilize the primary, without getting interference fringes generated by the secondary. This is where the thickness of the beamsplitter itself comes into play: at any given angle, the split will be more pronouced as thickness increases. With pellicles, this is next to impossible since the primary and secondary surfaces are only .* mils apart. For use in research that doesn't involve any of the characteristics of holography, this doesn't matter -- so that's why you see them out there. Of course, drum-head resonance and vibration is another matter altogether. I've worked with a few cubes and they are simple enough . . . although I would believe the higher-priced, coated cubes would score higher with less power absorption. Bottom line (all things considered) nothing beats a nice collection (50-50, 60-40, 70-30) of standard glass-plate beamsplitters -- except maybe a nice circular Newport variable . . . complete with table mount. :-) Frank 208.59.249.8

Brian - Tue, Aug 28, 01 09:07:35 AM

So, you're saying the thicker the beamsplitter plate, the better? But doesn't the secondary reflection still cause unwanted interference anyway? I'd think it would still be best to use cube beam splitters whenever possible, although the plates are much cheaper and come in more ratios. -Brian 66.69.244.199

Colin Kaminski - Tue, Aug 28, 01 01:56:37 PM

Thicker beamsplitters displace the reflection farther from the original. When both beams get to the next mirror it is a simple matter to let one pass by an deflect the other. There is a thread in the old section where it is explained how to laminate glass to a beam splitter. You can also make HOE's work as beam splitters. 64.167.151.3

Sylvie - Tue, May 07, 02 11:05:28 AM

im doing a project for my physics class on three dimentional holograms, and i have to set up a hologram set, but i dont know what a laser splitter looks like (i have a book that shows me what the set up looks like, but the picture of the splitter looks just like the lenses...) so i was wondering if anyone knows a web site with a picture of a laser splitter in it. thanks! :) 204.101.28.29

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