A data delivery device includes a storage unit for storing data, a receiving unit for receiving, from a client terminal, a request to download data to be stored into the storage unit and information indicative of a present position of the client terminal, through a network. The system contains a plurality of channels place behind the electronic image assembly and preferably in conductive thermal communication with the image assembly. The base includes at least one coupling element formed in the base. The surface on the inside of the slope includes a curved surface. The average refractive index of the dielectric or semi-conductor layer is variable in a plane orthogonal to the direction of the stack so as to compensate the effects of the variation in the angle of incidence of the electromagnetic radiation on the transmission spectrum of the cavities.