Copper Vapor / Copper Halide lasers have been around for a long time. I was interested in making one when I was in high school and went to the library at a loca

Copper Vapor / Copper Halide lasers have been around for a long time. I was interested in making one when I was in high school and went to the library at a local college and photocopied a whole bunch of old books/articles on the topic. Copper Halide lasers are one of the easiest to build (optically) as they have really high gain. You can get away with poor reflectivity / poorly aligned mirrors. Sam's Laser FAQ has a lot on the topic https://www.repairfaq.org/sam/laserccb.htm https://www.repairfaq.org/sam/laserccb.htm