Graphene is a one-atom-thick sheet of carbon atoms arranged in a honeycomb lattice. It was first obtained by exfoliation of graphite in 2004 and has since evolved into a thriving research topic because of its attractive mechanical, thermal, and elect
rical properties. Graphenes unique electrical properties derive from the relativistic nature of its quasiparticles, resulting in exceptionally high electron mobility. Graphene promises to revolutionize many applications, ranging from solar cells and light-emitting devices to touch screens, photodetectors, microwave transistors, and ultrafast lasers.
Emerging technology based on artificial materials containing metallic structures has raised the prospect for unprecedented control of terahertz waves through components like filters, absorbers and polarizers. The functionality of these devices is sta
tic by the very nature of their metallic or polaritonic composition, although some degree of tunability can be achieved by incorporating electrically biased semiconductors. Here, we demonstrate a photonic structure by projecting the optical image of a metal mask onto a thin GaAs substrate using a femtosecond pulsed laser source. We show that the resulting high-contrast pattern of photo- excited carriers can create diffractive elements operating in transmission. With the metal mask replaced by a digital micromirror device, our photo-imprinted photonic structures provide a route to terahertz components with reconfigurable functionality.
A robust wedge setup is proposed to unambiguously demonstrate negative refraction for negative index metamaterials. We applied our setup to several optical metamaterials from the literature and distinctly observed the phenomena of negative refraction
. This further consolidates the reported negative-index property. It is found there generally exists a lateral shift for the outgoing beam through the wedge. We derived a simple expression for calculating this beam shift and interestingly, it provides us a strategy to quantitatively estimate the loss of the wedge material (Im[n]). Addition- ally, we offered a design of metamaterials, compatible with nano-imprinting-lithography, showing negative refractive index in the visible regime (around yellow-light wavelengths). The multi-layer- system retrieval was utilized to extract the effective refractive index of the metamaterial. It was also intuitively characterized through our wedge setup to demonstrate corresponding phenomena of refraction.
Metamaterials are patterned metallic structures which permit access to a novel electromagnetic response, negative index of refraction, impossible to achieve with naturally occurring materials. Using the Babinet principle, the complementary split ring
resonator (SRR) is etched in a metallic plate to provide negative epsilon, with perpendicular direction. Here we propose a new design, etched in a metallic plate to provide negative magnetic permeability mu, with perpendicular direction. The combined electromagnetic response of this planar metamaterial, where the negative mu comes from the aperture and the negative epsilon from the remainder of the continuous metallic plate, allows achievement of a double negative index metamaterial (NIM) with only one metasurface and strong transmission. These designs can be used to fabricate NIMs at microwave and optical wavelengths and three-dimensional metamaterials.
We investigate the influence of different metals on the electromagnetic response of fishnet metamaterials in the optical regime.We found, instead of using a Drude model, metals with a dielectric function from experimentally measured data should be ap
plied to correctly predict the behavior of optical metamaterials. Through comparison of the performance for fishnet metamaterials made with different metals (i.e., gold, copper, and silver), we found silver is the best choice for the metallic parts compared to other metals, because silver allows for the strongest negative-permeability resonance and, hence, for optical fishnet metamaterials with a high figure-of-merit. Our study offers a valuable reference in the designs for optical metamaterials with optimized properties.
