Telecom-style ND filters?

Hi, all,

I need some ND filters for a stabilized laser product I'm designing. Ideally it would be about 5 mm in size and less than 1 mm thick.

The fallback position is to use a polarizer, which I can get in that size, but I'd far prefer to pick a density and stick to it.

Oh, and it needs to be stable to ~10 ppm at 70 C over time scales of hours.

Any bright ideas?

Thanks

Phil Hobbs

Reply to
Phil Hobbs
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I sure don't see any smaller than 12.5mm at the places I can think of to look. sciplus has a 6mm red, but no detailed specs on it (but it's also too thick at 1.4mm) and it's not neutral density....and I find UK and German companies that claim to do custom filters.

A 5mm i.d. tube, some carborundum, water, putty to make a ring dam, a drill press, and a 2x2" or 1" round filter, depending what you can find that you like?

Reply to
Ecnerwal

Why not a partially transmitting metallic coating?

Reply to
Salmon Egg

At 0.6 mm thickness, I can cut it with dikes if I have a few tries. It's the thickness that's the real issue.

Thanks

Phil Hobbs

Reply to
Phil Hobbs

Sure thing, but it's for a product, and I need it soonish. Some nicely metallized Kapton would be the bee's knees.

Thanks

Phil Hobbs

Reply to
Phil Hobbs

I've got some plastic ND filter material. (made for theatrical lighting by Tiffin) It's only 4 mils (0.1mm) thick. It works out to

795 nm, but I haven=92t tested it beyond that. I think it=92s some sort of emulsion? and it gets =91flaky=92 at high power densities. I don=92t think it will meet your 10 ppm spec, but I=92d be happy to stick a few pieces in an envelope and you can try it.

George H.

Or evaporate metal onto a microscope cover slip?

Reply to
George Herold

Thanks, George, that would be great.

Theatrical lights are pretty warm, so that should survive 85C okay.

Cheers

Phil Hobbs

Reply to
Phil Hobbs

One of these times I'm going to have to get an evaporator, but the cheapest decent ones are around $15k, so it won't be today. At my PPOE I had an old Denton DV502A whose vacuum gauge used a 12AX7A. It worked fine after I replaced the hivac valve, but I couldn't fit it in my briefcase when I left. ;)

The filter material arrived today, thanks. It works pretty well at 1 um, at least as measured with a 1 um longpass filter and a lead salt vidicon camera (which was $279 on eBay minus a lens, and works perfectly with a 35 mm camera lens and an adapter).

What I'd like to have used was a piece of double-side polished silicon, but all my wafer boxes stayed behind too.

Cheers

Phil Hobbs

Reply to
Phil Hobbs

I don't know what the process for getting one is, but a friend at a university mentioned that a vacuum deposition system was on the used equipment list (for free, I had to have a stern talk with myself) when I asked about possible used fiber splicers. I could ask her to put the appropriate people in touch with you, if you like (it's a not unreasonable drive from your current locale.)

Reply to
Ecnerwal

Thanks, Lawrence, that would be fairly cool. I actually have enough space to put it in at this point, so if it doesn't need too much TLC, it might be a real win.

Cheers

Phil Hobbs

Reply to
Phil Hobbs

The tube was open to the vacuum? That sounds like a cheap vacuum gauge.

George H.

Reply to
George Herold

No, it was the amplifier for a thermocouple gauge.

Cheers

Phil Hobbs

Reply to
Phil Hobbs

Oh, A Pirani gauge? I've always wanted to build one of those.

George H.

Reply to
George Herold

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