Virtually everything, and I mean everything in your post was wrong, but I still enjoyed the hell out of it.

Laser scientists know that if you use (a well anti-reflection coated) Ge window or lens to transmit a high power CO2 laser beam, slight absorption heats it a little. Heating it a little makes it more absorptive. So it heats a little more. And so forth, until the motherf——r cracks: “thermal runaway.”

Guess why? You are going to be a good experimental physicist eventually. Eventually. I spent two years blowing up homemade nitrogen lasers at Berkeley. Keep posting!