Meta-model-based multi-objective optimization for robust color reproduction using hybrid diffraction gratings

International audienceWe propose an efficient and versatile optimization scheme, based on the combination of multi-objective genetic algorithms and neural-networks, to reproduce specific colors through the optimization of the geometrical parameters of metal-dielectric diffraction gratings. To illustrate and assess the performance of this approach, we tailor the chromatic response of a structure composed of three adjacent hybrid V-groove diffraction gratings. To be close to the experimental situation, we include the feasibility constraints imposed by the fabrication process. The strength of our approach lies in the possibility to simultaneously optimize different contradictory objectives, avoiding time-consuming electromagnetic calculations

Leaky mode analysis of luminescent thin films: the case of ZnO on sapphire

Zinc oxide (ZnO) epitaxial thin films grown on c-sapphire substrates by pulsed laser deposition were investigated using angle and polarization-resolved photoluminescence spectroscopy. Side-emission spectra differed significantly from surface-emission spectra in exhibiting dominant, narrow, polarization-resolved peaks. These spectral features were attributed to leaky substrate modes in the layers. Observations were first verified using transmission calculations with non-adjustable parameters, which took into account the dispersion, the anisotropy of the ZnO refractive index and the dependence on film thickness. Results were consistent with Fabry-Perot-like interference being the origin of the distinctive ZnO luminescence observed at grazing incidence angles. A second analysis, based on the source terms method, was used in order to retrieve the bulk emission properties, including the wavelength-dependent quantum yield and the emission anisotropy. While ZnO thin films were considered here, this analysis method can be extended to any luminescent thin film of similar geometry, demonstrating the potential of leaky mode analysis for probing passive and active material properties

Wavelength-scale stationary-wave integrated Fourier-transform spectrometry

Spectrometry is a general physical-analysis approach for investigating light-matter interactions. However, the complex designs of existing spectrometers render them resistant to simplification and miniaturization, both of which are vital for applications in micro- and nanotechnology and which are now undergoing intensive research. Stationary-wave integrated Fourier-transform spectrometry (SWIFTS)-an approach based on direct intensity detection of a standing wave resulting from either reflection (as in the principle of colour photography by Gabriel Lippmann) or counterpropagative interference phenomenon-is expected to be able to overcome this drawback. Here, we present a SWIFTS-based spectrometer relying on an original optical near-field detection method in which optical nanoprobes are used to sample directly the evanescent standing wave in the waveguide. Combined with integrated optics, we report a way of reducing the volume of the spectrometer to a few hundreds of cubic wavelengths. This is the first attempt, using SWIFTS, to produce a very small integrated one-dimensional spectrometer suitable for applications where microspectrometers are essential

Hybrid plasmonics waveguides for light nanofocusing

International audienc

Ultrahigh-quality factor silicon on insolator microdisk resonator characterized by optical near-field

International audienc

Analyse modale et spectrale de structures photoniques par cartographie optique de champ proche

International audienc

Optical near field in integrated plasmonics on silicon photonics

International audienceThe integration of plasmonic nanostructures on silicon photonics enhances the photonic properties and functionalities of optical devices such as silicon photonic waveguides in the near infrared spectrum. Indeed, the use of electromagnetic surface waves associated with charge density waves on the surface of a conducting material (i.e. surface plasmons-polaritons) could confine and therefore enhance the local electromagnetic field relative to the electromagnetic field in a silicon photonic waveguide. In such a hybrid plasmonic-photonic integrated platform, the surface plasmons-polaritons are used for short-distance and strong interaction with matter while the photonic modes in silicon photonic waveguides are used for long-distance propagation of information. The integration of the plasmonic nanostructures and the photonic waveguides is based on evanescent directional coupling. Due to the subwavelength confinement of the electromagnetic fields in the plasmonic structures, optical near field measurements with the use of near-field scanning optical microscopes (NSOM) are required to reveal and to understand the propagation characteristics of light in integrated plasmonic devices on silicon photonics. The aim of this contribution is to present and to discuss the optical near field images of some integrated plasmonic devices. The interpretation of NSOM images provides a rich understanding of the physical mechanisms involved in plasmonic-photonic integrated structures

Réseaux de résonateurs pour la photonique sur silicium, applications au multiplexage en longueur d'onde

Le développement de la micro-électronique a permis d'obtenir des débits d'information très importants. Aujourd'hui, ces débits sont limités par la bande passante des interconnexions électriques utilisées et l'usage de lien optique devient nécessaire pour atteindre des débits supérieurs. Pour parvenir à réaliser cet objectif, de nouvelles briques de bases sont nécessaires comme des lasers, des modulateurs, des photodétecteurs et des dispositifs de guidage et de routage de la lumière. Toutes ces briques doivent être compatibles avec les procédés de fabrication CMOS. Cette thèse porte sur l'étude et le développement de composants à base de résonateurs circulaires permettant d'offrir des solutions alternatives aux dispositifs existants dans le domaine du multiplexage en longueur d'onde pour la photonique sur silicium. L'étude de résonateurs unique sur un wafer entier a permis de mettre en évidence la nécessité de la présence de dispositifs de régulation thermique pour compenser les variations technologiques. Les résultats de simulation et les dispositifs expérimentaux montrent que l'utilisation de réseaux de résonateurs permet de réaliser des opérations de filtrage large bande, avec des pertes très faibles. Basé sur ce principe, un multiplexeur 8 canaux a été fabriqué et caractérisé. Il répond aux spécifications télécoms. Ce type de composant est un candidat idéal pour permettre le développement du multiplexage en longueur d'onde dans le domaine de la photonique sur siliciumThe development of the micro-electronics industry has given access to very high data transmission rates. Currently, these data rates are limited by the electrical interconnection bandwidth and it will soon be necessary to use optical links to obtain higher data rates. To attain this objective, new building blocks must be developed such as lasers, modulators, photo-detectors, wave-guides and routing devices which must all be fully compatible with the CMOS processing. This doctoral thesis concerns the study and development of new components based on circular resonators arrays, which offer alternative solutions to existing devices in the field of wavelength division multiplexing for silicon photonics. The study of single ring resonators over the entire surface of a wafer shows that the use of thermal regulation is required to compensate for fabrication variations. Results of simulations and experiments show that arrays of circular resonators allow broadband filtering with very low loss. Based on this principle, an 8 channel multiplexer is demonstrated conforming to telecoms specifications. This kind of device is a potential candidate for use in the development of wavelength division multiplexing in silicon photonicsTROYES-SCD-UTT (103872102) / SudocSudocFranceF

Interferometry enhanced optical near field microscopy and spectroscopy

International audienc

Nano-optics for photonics: from optical field mapping to integrated spectroscopy and light condensing

International audienc