Just for clarity, I think the guy whose page I referred to did not split apart the layers of a DVD, in fact I think he used part of a CD. The suggestion of splitting apart the layers of a DVD was from me, since it is something that I noticed occurring when I chopped up an unwanted DVD that had some confidential stuff on it. I have not tried making one of those spectrometers so my ideas may not work as well as those of that guy who actually tried it for himself.
Chris