Short-Pulsed Wavepacket Propagation in Ray-Chaotic Enclosures

Wave propagation in ray-chaotic scenarios, characterized by exponential sensitivity to ray-launching conditions, is a topic of significant interest, with deep phenomenological implications and important applications, ranging from optical components and devices to time-reversal focusing/sensing schemes. Against a background of available results that are largely focused on the time-harmonic regime, we deal here with short-pulsed wavepacket propagation in a ray-chaotic enclosure. For this regime, we propose a rigorous analytical framework based on a short-pulsed random-plane-wave statistical representation, and check its predictions against the results from finite-difference-time-domain numerical simulations.Comment: 11 pages, 11 figures; minor modifications in the tex

Grating-Coupling-Based Excitation of Bloch Surface Waves for Lab-on-Fiber Optrodes

In this paper, we investigate the possibility to excite Bloch surface waves (BSWs) on the tip of single-mode optical fibers. Within this framework, after exploring an idealized, proof-of-principle grating-coupling-based scheme for on-tip excitation of BSWs, we focus on an alternative configuration that is more robust with respect to fabrication-related non-idealities. Subsequently, with a view towards label-free chemical and biological sensing, we present a specific design aimed at enhancing the sensitivity (in terms of wavelength shift) of the arising resonance with respect to changes in the refractive properties of the surrounding environment. Numerical results indicate that the attained sensitivities are in line with those exhibited by state-of-the-art plasmonic bioprobes, with the key advantage of exhibiting much narrower spectral resonances. This prototype study paves the way for a new class of miniaturized high-performance surface-wave fiber-optic devices for high-resolution label-free optical biosensing, and represents an important step forward in the "lab-on-fiber" technology roadmap.Comment: 15 pages; 9 figures; 3 tables (minor revisions in the title and text

Electromagnetic tunneling of obliquely-incident waves through a single-negative slab paired with a double-positive uniaxial slab

We show that, under appropriate oblique-incidence and polarization conditions, the inherent opaqueness of a homogeneous, isotropic single-negative slab may be perfectly compensated (in the ideal lossless case) by a homogenous, anisotropic (uniaxial) double-positive slab, so that complete tunneling (with total transmission and zero phase delay) occurs. We present an analytical and numerical study aimed at deriving the basic design rules, elucidating the underlying physical mechanisms, and exploring the role of the various involved parameters.Comment: 29 pages, 10 figure

Paired cut-wire arrays for enhanced transmission of transverse-electric fields through sub-wavelength slits in a thin metallic screen

It has recently been shown that the transmission of electromagnetic fields through sub-wavelength slits (parallel to the electric field direction) in a thin metallic screen can be greatly enhanced by covering one side of the screen with a metallic cut-wire array laid on a dielectric layer. In this Letter, we show that a richer phenomenology (which involves both electric- and magnetic-type resonances) can be attained by pairing a second cut-wire array at the other side of the screen. Via a full-wave comprehensive parametric study, we illustrate the underlying mechanisms and explore the additional degrees of freedom endowed, as well as their possible implications in the engineering of enhanced transmission phenomena.Comment: 4 pages, 8 figures; slight corrections in Figs. 1, 2, and

Electromagnetic tunneling through a single-negative slab paired with a double-positive bi-layer

We show that resonant tunneling of electromagnetic fields can occur through a three-layer structure composed of a single-negative (i.e., either negative-permittivity or negative-permeability) slab paired with bi-layer made of double-positive (i.e., positive permittivity and permeability) media. In particular, one of the two double-positive media can be chosen arbitrarily (even vacuum), while the other may exhibit extreme (either near-zero or very high) permittivity/permeability values. Our results on this counterintuitive tunneling phenomenon also demonstrate the possibility of synthesizing double-positive slabs that effectively exhibit single-negative-like wave-impedance properties within a moderately wide frequency range.Comment: 5 pages, 5 figures (minor revisions