So, it turns out that 8 watts is a lot of laser. Since it is all focused on a spot only 50 um wide, this comes out to about 4 GW/m^2. That’s about four million times brighter than the Sun (at 1 Au). That much energy can do a lot of interesting things, like transform metals into a highly reflective bifurcated crystalline mess.
Even defocused to a spot a few cm wide at the lowest setting (10 mW) it produces a spot almost too bright to look at. The coherent light shimmers dangerously, dancing with coruscating interference. Even laser glasses (which reduce the intensity to one in 10 million) can’t protect you fully. The reflected light at full power can burn tracks in your retina right through the filters. I got a headache every day from the light that was reflected reflected off the surface, and then off the walls, leaking in to my peripheral vision around the edges of the laser glasses.
Given the extreme danger of an active laser, did I end up playing around with it? Of course I did! I found you can cut 1/8″ dowels in about half a second. It will bore a hole through a half inch of wood in less than 1/10 of a second. Most metals reflect the 532nm light fairly well, so I wasn’t able to etch my pencil eraser holder. The eraser itself burnt well, as did the wood body. The graphite seemed immune to the laser. It either reflected or radiated the energy with an insane efficency, and I couldn’t put a dent in it. (Maybe there’s a market for graphite laser armor?) Black zip ties burnt almost comically well, even when submersed in water. Pretty much anything that absorbs green light goes up in smoke instantly when it’s on the spot.
The moral of the story? Lasers are so bright! Oh, and the business testing worked as well. The customer was quite pleased, and we may be seeing more lasers coming through in the future. Remember kids: Always wear the appropriate safety gear, and then enjoy the dangerous stuff!