We introduce graphene-based hyperbolic metamaterial for terahertz frequencies. The LDOS as well as the scattered power by a microsphere at its surface are enhanced by orders of magnitude, and controlled via chemical potential. © 2013 The Optical Society.

We investigate the power emitted by a two-dimensional array of impressed dipoles above a hyperbolic metamaterial (HM). Transmission line formalism of TM/TE spectral plane waves is used to model the scattering from the HM substrate. We show that the HM enhances the amount of emitted power which is mostly absorbed by the HM. © 2013 IEEE.

High impedance surfaces (HISs) have been proposed and used as substrate for dipoles for realizing low-profile antennas. Here, we show that HISs can be used directly as low-profile antennas with a single feed point, without any dipole on top. The structure is made of only two metallic layers, the patterned surface and the ground plane below, at a subwavelength distance. We analyze two possible feeding mechanisms of an HIS made of dogbone-shaped conductors, though the ideas proposed here can be applied also to other HIS structures. We show that broadside gain of the order of 7-11 dBi can be obtained. We also explain that radiation of the HIS is in part related to a TM-like leaky wave with attenuation constant that is not as small in contrast to other standard high-gain leaky-wave antennas. © 2006 IEEE.

We first introduce the formulation of 2D periodic dyadic Green's function to account for all the field contributions required to thoroughly describe the physics of a 2D array of nanospheres on top of a multilayered substrate. Then, we analyze substrate effects onto complex modes and optical properties of 2D arrays of linear trimers of plasmonic nanospheres and show that Fano resonant features appear for oblique TM-polarized plane wave incidence illumination. These features are attributed to the forced excitation of free modes supported by the array, here computed via modal analysis. We observe strengthened Fano features due to the presence of the multilayered substrate. © 2013 IEEE.

We analyze both theoretically and experimentally subwavelength focusing by using a planar hyperbolic metamaterial (HM) at microwave frequencies. The proposed HM consists of microstrip transmission lines (TLs) loaded by lumped components and exhibits a very flat wave vector iso-frequency dispersion diagram over a wide frequency range, and thus able to transport spectral component with large wavenumbers. This flatness is here exploited to provide subwavelength focusing with a full width half maximum (3-dB power width) of about λg/31 and λg/ 19 at 0.5 and 1 GHz, respectively, where λg is the guided wavelength in the TL microtrip grid. Numerical simulation results are in good agreement with measurement ones. Moreover, we also investigate the capability of the proposed HM to resolve sources with subwavelength distance of about λg / 6 and λg / 3 at 0.5 and 1 GHz, respectively.

Plasmonic nano antennas like dimers, bowties, and others have been investigated for their capability to provide a strong near-field enhancement when illuminated by external light. Traditionally these nano antennas, isolated or arrayed, are placed on a substrate and used in spectroscopy techniques. Surfaces made of such plasmonic nano antennas have been very useful, for example for surface enhanced Raman scattering, providing various orders of magnitude of enhanced sensitivity. These instruments however are not economic and are often not mobile since surfaces require an external beam illumination and the Raman scattering is detected by a large aperture microscope. We propose a technique where optical plasmonic nano antennas are located in proximity of silicon based waveguides that provide both for illumination and detection channels. The evanescent field surrounding the waveguide is capable to excite the proximity resonant nano antenna and generate the very strong field enhancement in the antenna gaps. Intensity enhancement reaches three or four orders of magnitude. Such nano antennas are used also for detection schemes and they provide very high sensitivity to molecular scattering, for example, when molecules are placed in the antenna 'hot spot'. A couple of different silicon based waveguide will be investigated with coupling to various possible plasmonic nano antennas. First we investigate the field enhancement and then the coupling to waveguide modes.

Plasmonic nano antennas like dimers, have been investigated for their capability to provide a strong near-field enhancement when illuminated by external light. Traditionally these nano antennas, isolated or arrayed, are placed on a substrate and used in spectroscopy techniques. Surfaces made of such plasmonic nano antennas have been very useful for applications like surface enhanced Raman scattering in which it provides various orders of magnitude of enhanced sensitivity. These instruments however are not economic and are often not mobile since surfaces require an external beam illumination and the Raman scattering is detected by a large aperture microscope. The goal of this paper is to combine nano antennas made of gold dimers with integrated waveguide to make a spectrometer which has low cost and volume in comparison with the structure mentioned above. A technique in which optical plasmonic nano antennas are located in proximity of silicon nitride waveguide is proposed that is useful both for illumination and detection channels. The waveguide evanescent field, which is decaying outside of the waveguide, excites the dimer and causes it to resonate which results in a very strong electric field enhancement of approximately 25 times in the antenna gap. Also the coupling effect of dimer resonance on waveguide modes is investigated. To show the efficiency of the proposed structure, full wave analysis has been done and its results are compared with the multilayer structure case. The simulation results demonstrate that this structure can be designed and fabricated for the purpose of spectroscopy application.