Energy transmission

Disclosed are radiant energy transmitting devices operative selectively in concentrative and emissive modes, having transmitting elements including radiant energy transmitting and guiding surfaces at the interface of media of differing indices of refraction for radiant energy. Surfaces generally are of a concavely sloping configuration consistent with reflecting, for example, extremal energy rays entering the element from within a defined field of acceptance at an energy inlet onto an energy trap or, in the alternative, extremal rays from an energy source through an energy outlet within a defined field of emission. The energy source or trap is preferably an energy transducer such as a photoelectric device.