Biomedical subjects

Philippe Lalanne

Publications and source records attributed to Philippe Lalanne.

5 recordsLinked to original sources

PubMed2005

Perfectly matched layers as nonlinear coordinate transforms: a generalized formalization.

A modified formulation of Maxwell's equations is presented that includes a complex and nonlinear coordinate transform along one or two Cartesian coordinates. The added degrees of freedom in the modified Maxwell's equations allow one to map an infinite space to a finite space and to specify graded perfectly matched absorbing boundaries that allow the outgoing wave condition to be satisfied. The approach is validated by numerical results obtained by using Fourier-modal methods and shows enhanced convergence rate and accuracy.

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PubMed2004

Broadband blazing with artificial dielectrics.

The efficiency of conventional diffractive optical elements with échelette-type profiles drops rapidly as the illumination wavelength departs from the blaze wavelength. We use high dispersion of artificial materials to synthesize diffractive optical elements that are blazed over a broad spectral range (approximately 1 octave) or for two different wavelengths.

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PubMed2004

Photonics: tuning holes in photonic-crystal nanocavities.

One challenge in photonics is strongly to confine light in small volumes in order to increase light-matter interaction. Akahane et al. propose a new concept for increasing the lifetime of this interaction, based on tailoring of the Fourier spectrum of cavity modes, which they believe is demonstrated by the surprising enhancement (roughly tenfold) of the quality factor Q of the cavity as a result of fine-tuning the mirror-hole geometry in a photonic-crystal nanocavity. Here we question the validity of their concept and argue that the improvement in Q is due to an increase in the impedance wave matching at the cavity edges and to a slow-wave effect. This alternative interpretation opens the way to new cavity designs.

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PubMed2002

Negative role of surface plasmons in the transmission of metallic gratings with very narrow slits.

It is generally admitted that the extraordinary transmission of metallic grating with very narrow slits is mainly due to the excitation of surface plasmons on the upper and lower interfaces of the grating. We show that the surface plasmon contribution is not the prime effect and that waveguide mode resonance and diffraction are responsible for the extraordinary transmission. Additionally and surprisingly, we reveal that the transmittance of subwavelength metallic gratings is always nearly zero for frequencies corresponding to surface plasmon excitation. This finding implies that surface plasmons play a negative role in the transmission.

Journal Article↗

PubMed2002

Stable and efficient bloch-mode computational method for one-dimensional grating waveguides.

We present a stable and efficient method for the Bloch-mode computation of one-dimensional grating waveguides. The approach uses the Fourier modal method and the S-matrix algorithm to remove numerical instabilities. The use of perfectly matched layers provide a high accuracy. Numerical results obtained for different lamellar grating waveguides and for both TE and TM polarizations illustrate the performance of the approach.

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