Natural Science Forum / Physics / Optics / May 2005

I am looking for an optical filter for a flourescence experiment. The
excitation wavelength is 365nm, and the emission wavelengths are
between 400 and 500nm. I would like to find a filter for the receving
optics which blocks 365nm (less than .01% transmission) and passes
400nm to 500nm (greater than 90% transmission).

Surprisingly, I have found only ONE material which does this. Yes,
schott, hoya, etc.. make colored filter glass specificaly GG400 and the
like, but that glass AUTOFLUORESCES when exposed to 365nm and is
basically worthless for this experiment.

The one material I have found which does a TERRIFIC job is the plastic
that UVEX clear safety glasses are made of. Its cheap, it does not
autofluoresce, and it has fantastic 365nm blocking and 400nm pass
through. The blocking at 365nm is so strong, I can actually put the
excitation source and the receiever butted up against each other (the
excitation LED shining directly into the receiver an inch away) and if
I put the clear safety glasses between them the 'signal' drops to
almost nothing, from completely saturated! Amazing!! Especially
considering this is a ultra-high gain lock-in amplifier!

I called UVEX and the person I talked to didn't know anything about the
material. I have read on the internet that it may be made by rohm and
haas.

Please, does anyone know of a filter that has these charateristics, or
a source for the same kind of plastic used in UVEX sunglasses?

Yes, I know I can just use the saftey glasses, but this device will
become a commercial one, and I don't think cutting up safety glasses
for each unit is realistic.