- Oct 6, 2015
The window on the front of the emitter just like the can windows don't like to be contaminated.
That's 1 factor, another may be humidity.
Looking at the emitter I don't know that oxygen could get at the gain medium, I think it has a tiny window, but contamination is an issue.
The emitter is on the right, I think it has a window, but it likes to be clean or it will pop/crack.
whauu amazing pictures