'Laser' was an acronym. 'Light Amplified by the Systematic Excitation of Radiation.' given that visible light and IR are all part of the electro-magnetic spectrum it doesn't really matter what part of it, your going to get energy losses.
One question you should consider, what is a fusion beam? Ohh it turns up all over sci-fi, but what is it? A beam of particles undergoing fusion? It just sounds wrong, aside from being inherently impossible of course.
