Daniel Maystre

Enhanced SPR sensitivity using periodic metallic structures

A sinusoidal silver grating is used to create a six-fold enhancement of the SPR response compared to a flat surface. The grating parameters are chosen to create a surface plasmon bandgap and it is shown that the enhancement of the sensitivity to bulk sample index occurs when operating near the bandgap. The Kretschmann configuration is considered and the Boundary Element Method is used to generate the dispersion curves.

Total absorption of unpolarized light by crossed gratings

We present both experimental and numerical data showing the absorption of unpolarized, normally incident light by a gold crossed grating having a shallow sinusoidal profile. We show furthermore that the total absorption of unpolarized light can be achieved for an angle of incidence of 30 degrees with a crossed grating having its period adjusted appropriately from the normal incidence case to preserve the plasmonic resonance responsible for the enhanced absorptance. We contrast the process for achieving high absorptance in the principal plane of incidence aligned with the grooves of one of the gratings, with that for the principal plane at 45 degrees to each grating.

Lossy Lamellar Gratings in the Quasistatic Limit

We use a rigorous formalism for lossy lamellar gratings to establish the validity of the quasistatic approximation for this structure in the limit as its period d becomes much finer than the wavelength u of incident light. In the quasistatic limit, the grating behaves like a uniaxial film in its interaction light, its principal refractive indices being given by simple formulae. We show numerically that the quasistatic model of the grating is accurate to better than an absolute tolerance of 0·005 if u/d>40. In the case of perfectly conducting lamellar gratings, we show that the model of a uniaxial film cannot be used in the quasistatic limit. This invalidates the optical model of Yeh for wire-grid polarizers.

Grating Enhanced Second Harmonic Generation Through Electromagnetic Resonances

This paper is concerned with surface enhanced second harmonic generation through delocalized electromagnetic resonances such as surface plasmons or guided waves at bare or coated metallic gratings. The formalisms presented are rigorous in the sense that the groove depth of the grating is not considered as a perturbative parameter. This allows us to show that there exists an optimum groove depth of the grating for which the enhancement of the second harmonic efficiency, as compared to the flat case, is the greatest. Shallow modulated gratings (10 -1) lead to optimum enhancement as high as 105. Emphasis is placed on the effect of the periodicity and of the profile of the grating on this optimum enhancement.

On a General Theory of Anomalies and Energy Absorption by Diffraction Gratings and Their Relation with Surface Waves

The authors generalize a previous theory to study the phenomenon of absorption of plane waves by a grating working with several spectral orders. The theory allows predicting, with the aim of a simple formula, the shape of various kinds of grating anomalies, as well as the shape of the total diffracted energy curve. The use of a convenient matrix, called S*S, leads to the introduction of the efficiency hyperellipsoid. This enables one to predict in a simple way a phenomenon of total absorption of a finite number of plane waves by a grating.

Plasmonic antiresonance through subwavelength hole arrays

It has been shown both experimentally and numerically that the phenomenon of extraordinary transmission through subwavelength hole arrays is generally associated with a drop in transmission located very close to it. Paradoxically, this antiresonant drop occurs at the wavelength that, at first glance, should provoke a resonant excitation of a surface plasmon propagating along the metallic surface of the screen. The present paper gives a theoretical demonstration of this phenomenon, which dispels the paradox. Our theory is supported by numerical calculations.

Whispering gallery modes and other cavity modes for perfect backscattering and blazing

We demonstrate the possibility to obtain perfect blazing both in Littrow and off-Littrow mountings using diffractive systems consisting of a plane metallic substrate and dielectric structures that can support cavity modes. The resonances are located at a relatively large distance between the metal and the dielectric structure, a condition that prevents the resonance increase of absorption. The high efficiency can be obtained in transverse electric or transverse magnetic polarization and at high incident angles. When cylindrical rods with circular cross-sections are used, the so-called whispering gallery modes can be used to provide the resonances, necessary for the blazing.

Why a harmonic solution for lossless, perfectly homogeneous, left-handed material cannot exist

In a preceding paper [J. Opt. Soc. Am. A21, 122 (2004)], we proposed proof of the nonexistence of harmonic solutions for a perfectly homogeneous left-handed material with both relative permittivity and relative permeability equal to -1 using the theorem of analytic continuation of an analytic function. The use of this theorem of analyticity has been questioned in a recent paper [Phys. Rev. E73, 046608 (2006)], arguing the possible inadequacy of the conditions of application of the theorem. We avoid the use of the analyticity theorem and propose a direct and simple proof of the nonexistence of such solutions. Furthermore, this proof is extended to any left-handed material with negative permeability and permittivity.

Phenomenological study of binding in optically trapped photonic crystals

We describe a phenomenological theory of the phenomenon of binding observed both experimentally and numerically when particles are trapped by an interference system in order to make a structure close to a photonic crystal. This theory leads to a very simple conclusion, which links the binding phenomenon to the bottom of the lowest bandgap of the trapped crystal in a given direction. The phenomenological theory allows one to calculate the period of the trapped crystal by using numerical tools on dispersion diagrams of photonic crystals. It emerges that the agreement of our theory with our rigorous numerical results given in a previous paper [J. Opt A8, 1059 (2006)] is better than 2% on the crystal period. Furthermore, it is shown that in two-dimensional problems and s polarization, all the optical forces derive from a scalar potential.

Ultrarefraction and negative refraction in metamaterials

In the recent years, many experimental and theoretical achievements have shown that meta-materials can simulate homogeneous materials with optical index less than unity or even negative. For example, a dielectric photonic crystal, used at the edge of a band gap, can generate phenomena of ultra-refraction (positive index less than unity) or negative refraction (negative index). Some applications of these phenomena will be shown, specially the design of directive antenna in the microwaves region. More recently, experimental and theoretical studies have been published on left-handed materials. These materials, which have a permittivity and a permeability equal to -1, have been the subject of controversies about their alleged property of making perfect lenses. It will be shown that such a perfect lens cannot exist. However, this kind of meta-material could be used for making better lenses than the best classical ones, a fact which could explain some experimental results. The vital influence of the size of the elementary cell on the performance of the lens will be pointed out. Finally, it will be shown that surprisingly, a left-handed material can be interpreted as a means to go through the mirror, as Alice in the novel of Lewis Carrol...