Virtually everything you "see" below 400 nm is fluorescence. Your retina and vitreous humour fluoresce at these wavelengths, so you can't even make an honest judgement whether you are "seeing" 400nm or something redder. This effect is especially pronounced if you have a very tiny source, like the output of an optical fiber. You will see a glow around the tip of the fiber coming from bulk fluorescence in your eye.
Cyparagon: All THG crystals will have SHG also. So, for instance, a tripled YAG will have a lot of 532 coming out (and some 266nm also). These systems require harmonic separators to pick the output.
ARG: temperature tuning in 405nm diodes is really bad, about 1nm per 20C. There are plenty of technical issues that crop up once you go below 10C or so (condensation is the first).
I think the only market that uses 375 is the science market, and it is, unfortunately, never going to blow up.
Cyparagon: All THG crystals will have SHG also. So, for instance, a tripled YAG will have a lot of 532 coming out (and some 266nm also). These systems require harmonic separators to pick the output.
ARG: temperature tuning in 405nm diodes is really bad, about 1nm per 20C. There are plenty of technical issues that crop up once you go below 10C or so (condensation is the first).
I think the only market that uses 375 is the science market, and it is, unfortunately, never going to blow up.