Visualizing the bidirectional optical transfer function for near-field enhancement in waveguide coupled plasmonic transducers.

We report visualizations of the bidirectional near-field optical transfer function for a waveguide-coupled plasmonic transducer as a metrology technique essential for successful development for mass-fabricated near-field devices. Plasmonic devices have revolutionized the observation of nanoscale phenomena, enabling optical excitation and readout from nanoscale regions of fabricated devices instead of as limited by optical diffraction. Visualizations of the plasmonic transducer modes were acquired both by local near-field excitation of the antenna on the front facet of a waveguide using the focused electron beam of a scanning electron microscope as a probe of the near-field cathodoluminescence during far-field collection from the back facet of the waveguide, and by local mapping of the optical near-field for the same antenna design using scattering scanning near-field optical microscopy as a probe of the near-field optical mode density for far-field light focused into the back facet of the waveguide.

Plasmonic near-field probes: a comparison of the campanile geometry with other sharp tips.

Efficient conversion of photonic to plasmonic energy is important for nano-optical applications, particularly imaging and spectroscopy. Recently a new generation of photonic/plasmonic transducers, the 'campanile' probes, has been developed that overcomes many shortcomings of previous near-field probes by efficiently merging broadband field enhancement with bidirectional coupling of far- to near-field electromagnetic modes. In this work we compare the properties of the campanile structure with those of current NSOM tips using finite element simulations.

A plasmonic dimple lens for nanoscale focusing of light.

Focusing electromagnetic energy to subwavelength dimensions has become an increasingly active field of research for a variety of applications such as heat-assisted magnetic recording, nanolithography, and nanoscale optical characterization of biological cells and single molecules using the near-field scanning optical microscopy technique. Double-sided surface plasmons in a metal-insulator-metal (MIM) geometry can have very small wavelengths for dielectric of thickness of less than 10 nm. A tapered dielectric structure sandwiched between metal can be used to efficiently couple electromagnetic energy from free space photons to the plasmonic wavelengths at the nanoscale.