Look at a bright enough 980 and you will see blue, I assume as it up-converts to 490. Not sure if it was the beam exapnder or my eyes...
She didn't tell her boss because she had disabled the safety switch, for some reason that seemed good at the time.
"A process in which two photons with the same frequency interact with a nonlinear material, are "combined", and generate a new photon with twice the energy of the initial photons. In some cases, almost 100% of the light energy can be converted to the second harmonic frequency. These cases typically involving intense pulsed laser beams passing through large crystals, and careful alignment to obtain phase matching. In other cases, like second harmonic imaging microscopy, only a tiny fraction of the light energy is converted to the second harmonic."