Giuseppe D'Aguanno

Negative refraction and sub-wavelength focusing in the visible range using transparent metallo-dielectric stacks

We numerically demonstrate negative refraction of the Poynting vector and sub-wavelength focusing in the visible part of the spectrum using a transparent multilayer, metallo-dielectric photonic band gap structure. Our results reveal that in the wavelength regime of interest evanescent waves are not transmitted by the structure, and that the main underlying physical mechanisms for sub-wavelength focusing are resonance tunneling, field localization, and propagation effects. These structures offer several advantages: tunability and high transmittance (50% or better) across the visible and near IR ranges; large object-image distances, with image planes located beyond the range where the evanescent waves have decayed. From a practical point of view, our findings point to a simpler way to fabricate a material that exhibits negative refraction and maintains high transparency across a broad wavelength range. Transparent metallo-dielectric stacks also provide an opportunity to expand the exploration of wave propagation phenomena in metals, both in the linear and nonlinear regimes.

Broadband absorbers and selective emitters based on plasmonic Brewster metasurfaces

(Received 20 November 2012; revised manuscript received 17 April 2013; published 10 May 2013)We discuss the possibility of realizing utlrabroadband omnidirectional absorbers and angularly selectivecoherent thermal emitters based on properly patterned plasmonic metastructures. Instead of relying on resonantconcentrationeffectsthatinherentlylimitthebandwidth,webaseourdesignonthecombinationoftwoinherentlynonresonant effects: plasmonic Brewster funneling and adiabatic plasmonic focusing. Using this approach, wepropose compact, broadband absorption and emission spanning terahertz, infrared, and optical frequencies, idealfor various energy and defense applications.DOI: 10.1103/PhysRevB.87.205112 PACS number(s): 78

Plasmonic Brewster angle: broadband extraordinary transmission through optical gratings.

Extraordinary optical transmission through metallic gratings is a well established effect based on the collective resonance of corrugated screens. Being based on plasmonic resonances, its bandwidth is inherently narrow, in particular, for thick screens and narrow apertures. We introduce here a different mechanism to achieve total transmission through an otherwise opaque screen, based on an ultrabroadband tunneling that can span from dc to the visible range at a given incidence angle. This phenomenon effectively represents the equivalent of Brewster transmission for plasmonic and opaque screens.

Group velocity, energy velocity, and superluminal propagation in finite photonic band-gap structures

We have analyzed the notions of group velocity

Dynamics of short pulses and phase matched second harmonic generation in negative index materials

{V}_{g}

Generalized coupled-mode theory for χ(2) interactions in finite multilayered structures

and energy velocity

Transmission function properties for multi-layered structures: application to super-resolution.

{V}_{E}

Plasmonic nanoparticles and metasurfaces to realize Fano spectra at ultraviolet wavelengths

for light pulses propagating inside one-dimensional photonic band gap structures of finite length. We find that the two velocities are related through the transmission coefficient t as

Birefringence in one-dimensional finite photonic bandgap structure

{V}_{E}=|t{|}^{2}{V}_{g}.

Field localization and enhancement of phase-locked second- and third-order harmonic generation in absorbing semiconductor cavities

It follows that