As for the patent which most resembles the Hot-Cat, it is probably this one: “Molecular hydrogen laser” US 7773656 to Mills. Of course, Rossi’s device is not a laser, but in operation it is closer than you may realize - unless you have followed the SPP discussions.
A picture is worth 1000 words… http://fusionfroide.ch/wp-content/uploads/2012/09/Rossis-HOT-CAT-reactor.jpg … and no, there is no indication that the photons seen here are coherent, or even superradiant. No evidence is possible since there is no lens. The IR light is coming through and/or heating a stainless steel end-cap. If the electrical input power is as low as claimed, then we are probably seeing superradiance, at least.
