Increased NCA Height Reveals New Lattice Plasmon Mode

A better understanding of the unique optical properties of core-shell nanostructures could impact the development of next-generation optical sensing and detection devices, as well as low-threshold and highly directional lasers.

Exploiting the accuracy of finite-difference time-domain numerical simulations, researchers from the University of Michigan and Massachusetts Institute of Technology studied core-shell SiO₂/Au nanocylinder arrays (NCAs) for the generation of lattice-plasmon modes (LPMs).

In research published in Optics Letters, they found that exciting the localized plasmon modes of the core-shell nanostructures resulted in novel photonic properties combining both the dielectric and metallic materials. “This has led us to consider putting the core-shell nano objects in an array to form a lattice plasmonic mode, which reflects the coherent coupling of individual core-shell nano objects,” said researcher Ya Sha Yi, of the University of Michigan and MIT.

Yi and researcher Linhan Lin, also of the University of Michigan, further found that increasing the nanocylinder array height triggered a new localized surface plasmon resonance mode along the nanocylinders. Since this new LPM is not mediated by the substrate, radiative loss could also be effectively suppressed in these core-shell NCAs, indicating the possibility of future applications in fluorescence enhancement and nanolasers, said Yi.

These new LPMs are important to the development of such devices because the new LPM is independent of the substrate, effectively eliminating the possible radiation loss from the potential substrate. The gold layer on the SiO₂ will be critical to fabrication, but a perfect gold coating is not required for dipole distribution associated LPM generation, the researchers said.

Financial support came from the University of Michigan and Demetra Energy, Europe.