Working with CO2 lasers can be an expensive proposition, especially if you need to fill the resonant cavity with so-called "laser gas" periodically. I had to do this to fire up a folded CO2 bench-top laser rated for 300 watts at the Air Force Weapons Laboratory in Albuquerque NM.
Laser gas is commercially available, but this lab had a large gas manifold with all manner of gas bottles attached. I looked up the usual recipe, evacuated a bottle with a mechanical vacuum pump to "pretty low" pressure, and then added-in the gases I needed, carefully watching the partial pressure of each additional gas to make sure I got the mixture correct. The CO2 gas was a real bitch-kitty because the regulator kept freezing up. Slow and easy does it for that one! I must have done something right because the laser "lit up" just fine when power was applied and a 10.6 μm beam appeared at the output port. My only experience with CO2 lasers up to that point was with a 5 W Sylvania sealed-tube laser that used fixed Brewster windows and external cavity tuning mirrors. This was a plug-and-play laser that I used for several years without any problems.
After I worked on-loan for a while in Albuquerque, UDRI called me back to Dayton to work on other things. The Air Force was going nowhere with chemical lasers mounted in airplanes. Too hard to maintain, extremely toxic gasses produced during lasing, and very difficult to get enough energy on-target from a few kilometers distance from the target to ensure a definite "kill" shot. IMHO, what really killed this program (if it is indeed dead, and not just buried in some black budget somewhere) was the Navy research into electromagnetic rail-gun technology. "One pound to Jupiter" one of my old supervisors once told me. In other words, rail guns shoot heavy projectiles that have substantial momentum. I have heard it is like a Volkswagen bus, hitting you from nowhere at supersonic velocity. Hard to defend against momentum when it is coupled with a huge amount of kinetic energy. I am glad I got out of that race before someone demanded results, i.e., a battlefield weapon system. Guns and bullets will always trump a bright smile, even if sincere, any day. Add in biological, chemical, and nuclear players and who needs Star Wars laser weapons?