The present invention provides an improved lamp, and lighting fixture incorporating such a lamp, wherein the lamp's envelope includes a special optical coating system configured to more effectively reflect infrared light back toward the lamp filament, thereby enhancing the lamp's luminous efficacy. Multiple embodiments are disclosed, including coating systems deposited on one or both surfaces of the lamp envelope and including coating systems incorporating either a dielectric coating alone or specific combinations of a dielectric coating and a transparent conductive coating.