A plasmonic structure comprises a substrate and an electro conductor provided in or on the substrate. The electro conductor comprises a first part configured to provide a first series of plasmon resonance modes (for incident radiation of a first wavelength) and a second part configured to provide a second series of plasmon resonance modes (for incident radiation of a second wavelength). The first and second parts are functionally connected in a linkage region, wherein the electro conductor is shaped such as to form a capacitive gap. The electro conductor is further configured to direct radiation incident on the plasmonic structure of the first wavelength predominantly toward a first direction and to direct radiation incident on the plasmonic structure of the second wavelength predominantly toward a second direction, in which the first direction and the second direction are separated by an angle of at least 60°.