I am wondering just which parts of the EM spectrum can we and can we still not lase in. For the purpose of this thread, I consider the visible pretty much covered. But what about the IR, is there any thing between 3 and 10 microns? What is lasable at longer wavelengths? Are masers available for certain lines only or do they cover a continuum? What about radio? ("raser"?) It that lasable? And what about the short wavelengths, where are we at in this area? Cheers.