Efficient optical coupling between nano- and macroscale areas is strongly suppressed by the diffraction limit. This work presents a possible solution to this fundamental problem via the experimental fabrication, characterization, and comprehensive theoretical analysis of structures referred to as ‘photonic funnels’. 

The funnels comprise hyperbolic metamaterial cores that support propagation of strongly confined modes and highly conductive cladding that prevents leakage of light through the structure’s sides. The funnels are realized in the important mid-infrared frequency range with a semiconductor-based designer metal platform. These results demonstrate the potential of the photonic funnel architecture for nanophotonic sensing applications with six orders of magnitude enhancement compared to a lossless high-index core funnel. 

This work has the potential to open numerous applications in microscopy, spectroscopy, communications, and sensing.