spectrometer

Haven't we had this discussion? Try googling 'grating spectrometer'. The grating will 'turn' the light by an angle that is related to the wavelength. So with a grating if you can measure an angle you know the wavlength.

George H

That's a narrow range. What resolution do you need within it?

Also, it's not a range your eye will make much of. So you almost certainly will be using some method to capture it on CCD or else using fluorescence to down-convert it along with an adjusting monochrome spectrograph. What are your plans here?

Also, be aware that not all glasses and quartz will pass those wavelengths, should you have to pass it through a lens. Some quartz glass (Q3) doesn't start passing much through it until about 400nm. So be aware of that issue, as well.

References? There are a few things out there about them, not a lot of good, useful material though. I haven't used CDs much, but I have worked with DVD-R, DVD+R, and DVD-RW disks. The DVD-R/+R types have a nasty absorption band in the red, but the DVD-RW appears to not use that region for absorption. But I haven't been looking to use these for as short as 350nm. I have, though, been able to see lines at

The really nice thing about DVDs is that they are made at .74um or about 1350 lines/mm, which is nice enough that I seem to be able to resolve out a yellow mercury pair at 577nm and 579nm. CDs can't do that because they use 1.6um or about 625 lines/mm.

Some things to consider and research while you consider this. DVDs, I think, are coated with a relatively thick layer of plastic on both sides and this may dampen shorter wavelengths more than with CDs, which I seem to recall have less thickness on the active side. Also, pre-pressed CDs (not writable) use aluminum for the reflective surface (I think) and while aluminum is a great reflector at longer wavelengths, my memory from telescope work (comparing silver and aluminization) is that aluminum absorbs somewhat up near the shorter end enough that sometimes I preferred silvering. So research that aspect. The wonderful thing about CDs and DVDs is that they are VERY CHEAP to play with, so it doesn't cost a lot to just go and find out if they work for your needs.

You will need to consider calibration, as well. For this, you will need a light source that produces bands for that purpose. And here again you are lucky, as a mercury-argon lamp is great. When it first fires up, you will get some great mercury lines, including some easily recognized doublets and that should allow you to do a pretty good job of wavelength calibration, if you need that. They don't cost much, either -- I bought a good one for $8, a few years ago. The mercury lines will appear strong, at first, and then the argon lines will come in strongly about a minute or two later on. Just turn it off, let it cool again, and turn it on to get the strong mercury lines a second or third time, if you need to.

I would imagine using them in conjunction with the CD/DVD. It costs almost nothing to try them and they may do an okay job at your wavelengths, though it's hard to say. 350nm is a bit short for some lens systems. But your lines might be bright enough with the camera's sensitivity. So that may still be fine. You can set all this up with a shoe box or even just some card-stock paper folded in the right way and with the angles computed for either the CD or DVD and the band you are looking for. Do you know how to calculate these things or build one? I may be able to help some, here.

I don't know of any, offhand. I'd suppose you could google this as well as anyone, though.

Jon

Have Fun! Rich