I had a friend, “Kevin” who got picked as a lab assistant for a guy making one of the first violet, and IIRC, picosecond lasers. It’s frickin’ laser beams so of course I had to ask way too many questions. They probably should have been using curtains but if they were he never said, and I’m sure laser safety has evolved with the wattage and commercialization, whereas this was a static benchtop system.

There were lots of mirrors and prisms and they has to calculate refraction off of them and stick carbon blocks everywhere that light transmission was less than 100% efficient so that no light could escape the system except via the target.