LASER Pyrogravure
Image By User:Eino81 – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=8003112 The original LASER invention (as I recall) was a glass like mineral ruby rod with a photo (xeon) flash tube wound around the outside. One end of ruby rod was reflective. The firing end was semi-reflective. I don’t think these were used as industrial LASERs. …