Hyperbolic metamaterials based on metal-dielectric thin layers

Metamaterials are artificial structures consisting of periodic sub-wavelength elements, they produce a particular electromagnetic response which often cannot be obtained from conventional media. One class of metamaterials called hyperbolic metamaterials (HMM) is widely studied nowadays due to their various applications such as subwavelength imaging and local density of states engineering.1 In this work, HMM consisting of alternating gold, copper, and niobium pentoxide layers was designed and fabricated with plasma assisted electron beam deposition technique. For the accurate description of this material opto-geometrical parameters of thin layers composing it were determined separately using reflection and transmission measurements. Afterward, the produced material was structured using focused ion beam milling and its influence on the Alexa Fluor 647 biomolecules spontaneous emission was studied experimentally with fluorescence correlation spectroscopy and time-correlated single photon counting techniques. Combining these techniques enable the measurement of the fluorescence lifetime reduction together with the brightness enhancement per molecule. The same measurements were previously done for the structured gold films3 which let us compare the results. HMM has shown significant emission enhancement compatible with the one produced by a single gold aperture which is known for its good plasmonic properties.

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