So part of the lack of visibility of the color through orange goggles in shorter wavelengths like 445nm is due to the fluorescence created which overpowers some of the blue that could be visible?
This could also be the case, although I wasnt actually saying that!
But yes the fluorescence could overpower any blue that would otherwise be visible. The combined wavelengths blue + fluorescence would appear more "white".
I was actually saying with the high OD in the blue the glasses let very little light through (445 & 405) and this coupled with the fact we have less sensitivity to these wavelengths would make a weak blue dot much harder to see. Again as you mentioned this weak blue would be then over powered by the fluorescence.
I have a green LED flashlight and the bright green color is white through the goggles. I guess it's not bright enough for the green to show through even with the lower OD at 532nm.
The white color that the green LED light becomes, is that a fluorescing effect, although it would be out of the range of fluorescing capability as you were mentioning. If it looks white through the goggles is there another mechanism for this other than fluorescence?
I cant categorically confirm this, but yes its possible that it's fluorescence mixed with green, as red light + green light gives yellow. So does the light appear white or yellow? With my 5 mW green through the glasses it appears yellow! Below is a general explanation of fluorescence:
Fluorescence can still occur with 532 but it is less common and even less so with red and IR. It will depend on the material absorbing the photons and its fluorescence quantum yield. Normally if you absorb a photon the transition is from a vibrationally excited ground state (Eo) to the first excited state (E1) also in a vibrationally excited state. This E1 then relaxes back to the vibrational ground state of E1 thus loosing some energy. Hence why emission (fluorescence) is at longer wavelengths.
If there is a good overlap of the wavefunctions between E1 and Eo there is a high probability of quick relaxation of the electron back to the ground state Eo and this can result in the emission of a photon at longer wavelength, if there is a large energy separation between the 2 electronic states. If the energy gap is small, ie in molecules excited by low energy photons, significant kinetic competition between internal conversion and fluorescence exists and much less radiative emission is seen.
As for a 650nm laser, is it not possible to have the OD high enough to make the dot look white through the goggles, it just remains red at higher OD's until it finally is just invisible because of the lack of fluorescing effect on the goggles with red wavelengths that would otherwise make the dot look white?
As there is negligible fluorescence at 650, effectively the only light youll see through the goggles from the dot will originate from the beam itself. If you increase the OD of the red glasses, which is easy to do (increase the concentration of dye molecules in the plastic) this red light will be much less visible to the point of you no longer being able to see the dot. As we need to see where we are pointing the OD is kept lower so we can still see some light.
I am really looking forward to getting my green colored red absorbing goggles from Dragon Lasers to see how their goggles act with 650nm light.
Id be interested to see the results! :beer:
Edit: Just had a look around and here is some further info if you're interested. Contains some pictorial representations with explanations:
http://en.wikipedia.org/wiki/Franck–Condon_principle
