I was using a pair of these safety goggles which appear to be quite popular among laser hobbyists:
They claim OD5 protection in the 190-540nm range. I have tested them with a blue 450nm diode. They work well and fully hide the beam and dot for low powers but above 1W I can see a faint yellow/greenish dot that gets brighter as I ramp the power up; at 5W it is quite visible (although still nothing compared to the unfiltered dot, I would imagine).
My question is, shouldn't the dot be completely filtered out, or at least show up as blue if it is just too bright for the goggles to fully attenuate? Why am I seeing a yellow dot being produced by a laser that produces only blue wavelengths? Is there some mechanism in the goggle lenses which diffuses the light and causes it to change wavelength as it is absorbed, or should I be worried about the yellow dot somehow being some unfiltered laser light coming from a supposedly blue laser?
I want to take precautions to correctly protect my eyes when working with powerful lasers so I think getting a better understanding of how these goggles work will help me to achieve this. Many thanks.
EDIT: when I say dot I am talking about the dot that the beam shines on a diffuse surface (wooden in my case). Obviously I am not directly looking into the beam.