Due to the small skin depth in metals at optical frequencies, their plasmonic response is strongly dictated by their surface properties. Copper (Cu) is one of the standard materials of choice for plasmonic applications, because of its high conductivity and CMOS compatibility. However, being a chemically active material, it gets easily oxidized when left in ambient environment, causing an inevitable degradation in its plasmonic resonance. Here, for the first time, we report a strong enhancement in the optical relaxation time in Cu by direct growth of few-layer graphene that is shown to act as an excellent passivation layer protecting Cu surface from any deterioration. Spectroscopic ellipsometry measurements reveal a 40–50% reduction in the total scattering rate in Cu itself, which is attributed to an improvement in its surface properties. We also study the impact of graphene quality and show that high quality graphene leads to an even larger improvement in electron scattering rate. These findings are expected to provide a big push towards graphene-protected Cu plasmonics.

Material loss diminishes the ability of a negative refractive index material to function as a superresolution lens. We find that the transmittance of a negative index slab can be greatly enhanced at a certain evanescent field spatial frequency if the imaginary parts of the permittivity and permeability in the slab can be tuned, even when the object, lens, and image domains have overall loss. This leads to a proposed method to image the farsubwavelength features of an object by reconstructing the evanescent part of its spectrum. (C) 2016 Optical Society of America

We present a fabrication method to achieve a graphene stack metamaterial, a periodic array of unit cells composed of graphene and a thin insulating spacer, that allows accumulation of the strong absorption from individual graphene sheets and low reflectivity from the stack. The complex sheet conductivity of graphene from experimental data models the measured power transmitted as a function of wavelength and number of periods in the stack. Simulated results based on the extracted graphene complex sheet conductivity for thicker stacks suggest that the graphene stack reflectivity and the per-unit-length absorption can be controlled to exceed the performance of competing light absorbers. Furthermore, the electrical properties of graphene coupled with the stack absorption characteristics provide for applications in optoelectronic devices.

We present a metal-dielectric stack ultraviolet (UV) bandpass filter that rejects the longer wavelength, visible spectrum and is thin and relatively insensitive to the angle of incidence. Parametric evaluations of the reflection phase shift at the metal-dielectric interface provide insight and design information. This nontrivial phase shift allows coupled Fabry-Perot resonances with subwavelength dielectric film thickness. Furthermore, the total phase shift, with contributions from wave propagation and nontrivial reflection phase shift, is insensitive to the angle of incidence. Filter passbands in the UV can be shifted to visible or longer wavelengths by engineering the dielectric thickness and selecting a metal with an appropriate plasma frequency.

We present the fabrication and characterization of a graphene stack that can function as the darkest material and serve as the basis for a new class of sensitive, high-speed photodetectors. (C) 2013 Optical Society of America

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text S. Kim, M. Man, M. Qi, and K. J. Webb, "Multilayer Metal-Dielectric Stack Ultraviolet Filter," in Frontiers in Optics 2013, I. Kang, D. Reitze, N. Alic, and D. Hagan, eds., OSA Technical Digest (online) (Optica Publishing Group, 2013), paper JW3A.30. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article