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Dive into the research topics where B. Djafari Rouhani is active.

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Featured researches published by B. Djafari Rouhani.


Optics Express | 2010

Simultaneous existence of phononic and photonic band gaps in periodic crystal slabs

Yan Pennec; B. Djafari Rouhani; E. H. El Boudouti; C. Li; Y. El Hassouani; J. O. Vasseur; N. Papanikolaou; Sarah Benchabane; Vincent Laude; A. Martinez

We discuss the simultaneous existence of phononic and photonic band gaps in a periodic array of holes drilled in a Si membrane. We investigate in detail both the centered square lattice and the boron nitride (BN) lattice with two atoms per unit cell which include the simple square, triangular and honeycomb lattices as particular cases. We show that complete phononic and photonic band gaps can be obtained from the honeycomb lattice as well as BN lattices close to honeycomb. Otherwise, all investigated structures present the possibility of a complete phononic gap together with a photonic band gap of a given symmetry, odd or even, depending on the geometrical parameters.


AIP Advances | 2011

Band gaps and cavity modes in dual phononic and photonic strip waveguides

Yan Pennec; B. Djafari Rouhani; C. Li; Jose M. Escalante; A. Martinez; Sarah Benchabane; Vincent Laude; N. Papanikolaou

We discuss theoretically the simultaneous existence of phoxonic, i.e., dual phononic and photonic, band gaps in a periodic silicon strip waveguide. The unit-cell of this one-dimensional waveguide contains a hole in the middle and two symmetric stubs on the sides. Indeed, stubs and holes are respectively favorable for creating a phononic and a photonic band gap. Appropriate geometrical parameters allow us to obtain a complete phononic gap together with a photonic gap of a given polarization and symmetry. The insertion of a cavity inside the perfect structure provides simultaneous confinement of acoustic and optical waves suitable to enhance the phonon-photon interaction.


Progress in Surface Science | 1998

GIANT STOP BANDS AND DEFECT MODES IN ONE-DIMENSIONAL WAVEGUIDE WITH DANGLING SIDE BRANCHES

B. Djafari Rouhani; J. O. Vasseur; A. Akjouj; L. Dobrzynski; M.S. Kushwaha; P. A. Deymier; J. Zemmouri

Abstract We investigate both the photonic and electronic band structure of a comb-like waveguide geometry in which dangling side branches are grafted along an infinite one-dimensional waveguide. In a periodic (superlattice like) waveguide, we report the opening-up of stop bands which originate both from the periodicity of the system and the resonant states of the grafted branches (which play the role of resonators). Wide gaps (narrow bands) can be obtained by grafting several dangling side branches at every node. The stop bands still remain even for identical constituent materials. We also propose a tandem structure composed of two or several successive combs which differ by their physical characteristics that allows an ultrawideband filter. This behavior results from the superposition of the bandgaps in the successive structures. The presence of a defect branch in the comb can give rise to localized modes inside gaps. These states appear as very narrow peaks in the transmission spectrum and therefore may have useful applications in the frame of photonic bandgap materials or electronic band engineering of nanostructures.


Journal of Physics: Condensed Matter | 1989

Localised acoustic waves associated with a planar defect in a superlattice

E. M. Khourdifi; B. Djafari Rouhani

The authors present a theoretical study of the existence of shear horizontal vibrations localised at a planar defect in a superlattice. Such a defect, which breaks the translational symmetry along the axis of the superlattice, is formed by a layer whose elastic parameters and thicknesses are different from those of the normal layers; it may result from inhomogeneities in the properties of the perfect superlattice. They show that localised shear horizontal modes associated with the planar defect may exist in the gaps of the superlattice or even below the bottom of the bulk bands and may in this case extend down to k/sub ///=0 (k/sub /// is the wavevector parallel to the layers). The dispersion relations of these waves are discussed as functions of the relative parameters of the superlattice and the planar defect. These results are qualitatively compared with those obtained in other surface and interface problems in which the existence of shear horizontal excitations have been investigated.


Journal of Physics: Condensed Matter | 2009

A birefringent reflector from a 1D anisotropic photonic crystal

N Ouchani; D Bria; B. Djafari Rouhani; A. Nougaoui

We demonstrate theoretically that a one-dimensional anisotropic photonic crystal can exhibit an absolute photonic band gap in which the propagation of light is prohibited for all polarizations and for a given incidence plane. Our structure is formed by the combination of a simple finite superlattice, composed of two alternating birefringent biaxial layers, with a cladding layer. The latter is made of the same material as one of the layers constituting the perfect superlattice, but with different orientation and thickness. We discuss whether the birefringence of the layers has a significant impact on the reflection gap. We have found that for reasonable values of structure parameters an absolute band gap can be obtained. Greens function method is used to derive the necessary expressions for our calculation. The effect of different parameters, namely, the orientation of the layers, the filling fraction, etc, is investigated to achieve a birefringent reflector.


Vacuum | 1999

Localized and resonant acoustic waves associated with a periodic array of supported wires

B. Djafari Rouhani; Abdelkrim Khelif

Abstract We developed a Green’s function formalism to investigate the localized and resonant acoustic modes of shear horizontal polarization associated with the surface of a substrate supporting a periodic array of wires. Each material is assumed to be an isotropic elastic medium. The calculation can be applied to an arbitrary choice of the shape and elastic parameters of the wires. The surface modes are obtained as well-defined peaks of the densities of states (DOS). In this paper, we calculate the dispersion curves of the surface modes for wires of parabolic section, and discuss their behaviour as a function of the elastic parameters, the height and the periodicity of the wires.


Archive | 1991

N-Layer Superlattice Phonons

L. Dobrzynski; A. Rodriguez; J. Mendialdua; D. J. Lockwood; B. Djafari Rouhani

N-layer superlattices are formed out of a periodic repetition of a unit cell containing N (N > 2) different slabs. Polytype superlattices made from three constituents (InAs — GaSb — AlSb) were proposed recently.1 We review here the studies of phonons in N-layer superlattices.2–9 A recent Raman determination10 of folded acoustic phonons in a four-layer superlattice is then compared with the theoretical results. We discuss also the existence of surface phonons for three-layer superlattices and the possible extensions of these studies to more complex composite materials.


Physical Review B | 2010

Dual phononic and photonic band gaps in a periodic array of pillars deposited on a thin plate

Y. El Hassouani; C. Li; Yan Pennec; E. H. El Boudouti; H. Larabi; A. Akjouj; O. Bou Matar; Vincent Laude; N. Papanikolaou; A. Martinez; B. Djafari Rouhani


Physical Review B | 1986

Effective dielectric and photoelastic tensors of superlattices in the long-wavelength regime.

B. Djafari Rouhani; J. Sapriel


Physical Review B | 1993

Raman scattering from folded acoustic phonons and photoluminescence in multilayer GaAs-AlAs superlattices.

D. J. Lockwood; R. L. S. Devine; A. Rodriguez; J. Mendialdua; B. Djafari Rouhani; L. Dobrzynski

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A. Akjouj

Centre national de la recherche scientifique

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J. O. Vasseur

Centre national de la recherche scientifique

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Vincent Laude

Centre national de la recherche scientifique

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Sarah Benchabane

University of Franche-Comté

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Yan Pennec

Lille University of Science and Technology

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A. Martinez

Polytechnic University of Valencia

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L. Dobrzynski

Lille University of Science and Technology

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M.S. Kushwaha

Benemérita Universidad Autónoma de Puebla

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