An illuminant comprising a transparent substrate layer with a first index of refraction, a connecting layer with a second index of refraction that differs from the first index of refraction, and a metallic, translucent layer, wherein the connecting layer is arranged between the substrate layer and the metallic layer, and wherein on the side facing the connecting layer the substrate layer comprises a plurality of decoupling structures suitable for decoupling light that propagates within the substrate layer from the substrate layer in the direction towards the metallic layer.