Tailoring of electromagnetic field localizations by two-dimensional graphene nanostructures.

Graphene has great potential for enhancing light-matter interactions in a two-dimensional regime due to surface plasmons with low loss and strong light confinement. Further utilization of graphene in nanophotonics relies on the precise control of light localization properties. Here, we demonstrate the tailoring of electromagnetic field localizations in the mid-infrared region by precisely shaping the graphene into nanostructures with different geometries. We generalize the phenomenological cavity model and employ nanoimaging techniques to quantitatively calculate and experimentally visualize the two-dimensional electromagnetic field distributions within the nanostructures, which indicate that the electromagnetic field can be shaped into specific patterns depending on the shapes and sizes of the nanostructures. Furthermore, we show that the light localization performance can be further improved by reducing the sizes of the nanostructures, where a lateral confinement of λ0/180 of the incidence light can be achieved. The electromagnetic field localizations within a nanostructure with a specific geometry can also be modulated by chemical doping. Our strategies can, in principle, be generalized to other two-dimensional materials, therefore providing new degrees of freedom for designing nanophotonic components capable of tailoring two-dimensional light confinement over a broad wavelength range.

Nanomaterials for field electron emission: preparation, characterization and application.

We review the current development in synthesis and deposition techniques of quasi-one-dimensional nanomaterials and recent achievements in the study of the field electron emission properties of these materials. Major findings are given from our recent experimental study of the field electron emission characteristics of carbon nanotubes, copper sulfide and silicon carbide nanorods. The study reveals that the above nanomaterials are promising candidates as cold cathode electron emitters. Furthermore, we review the recent development of techniques for growing and depositing the above nanomaterials in device structures. Typical device structures and their performance are also shown.