Surface-Wave-Assisted Beaming of Light Radiation from Localized Sources

In analogy to the well-known plasmonic bull's eye, we introduce here an all-dielectric mutilayered ring structure with high-directivity antenna capabilities. Radiated energy from organic emitters localized within the ring center is resonantly transferred to surface modes on the multilayer and then diffracted in the free space. The structure can be obtained by properly applying the Bragg law to a diffraction pattern defined in the Fourier plane as a superposition of "caustics". This approach allows designing diffractive structures producing a surface-mode-assisted beaming of radiation out of the sample with an arbitrary propagation angle in two dimensions. Specifically, we demonstrate that an anisotropically periodic ring structure can beam fluorescence emission with a tilt angle of 11.5 deg from the normal direction. The proposed use of surface modes for manipulating light at a subwavelength scale can represent an interesting alternative to the more conventional all-plasmonic approach.