Multi-colour reflective metagrating with neutral transparency for augmented reality.

This paper presents the design and experimental validation of an all-dielectric and transparent metagrating-based metalens. Leveraging multiple guided mode resonances simultaneously, the metagrating enables the generation of two or more spectrally narrow reflection peaks. These peaks are achieved through the precise engineering of guided mode resonances, allowing for the reflection of a comb of vibrant and saturated colours.

Numerical demonstration of surface lattice resonance excitation in integrated localized surface plasmon waveguides.

We numerically show that surface lattice resonances (SLR) in periodic localized surface plasmon (LSP) waveguides integrated on a dielectric waveguide can be excited via in-phase evanescent coupling, by incident propagation vector outside the light cone and without any constraint on the structural symmetry. FDTD simulations show that the coupling between wideband LSP resonances and narrowband SLR results in a Fano-like resonance, showing few nanometers large sharp spectral features that may be exploited for achieving new functions for integrated optics and sensing.

Optical spatiotemporal differentiator using a bilayer plasmonic grating.

As a key element in wave-based analog computation, optical differentiators have been implemented to directly perform information processing, such as edge detection and pulse shaping, in both spatial and temporal domains. Here, we propose an optical spatiotemporal differentiator, which simultaneously performs first-order spatial and temporal differentiation in transmission by breaking the mirror symmetry of a subwavelength bilayer metal grating. The spatial and temporal performance of the plasmonic differentiator is evaluated numerically using the output field profiles of an optical beam and pulse envelope, showing resolutions of ∼2µ and ∼50, respectively.

Broad-band plasmonic isolator compatible with low-gyrotropy magneto-optical material.

Integration of optical isolators remains one the main technological issues of photonic circuits despite several decades of research. We propose a radically new concept which enables performing broad-band isolation even in the case of low-gyrotropy material, opening the road to a new class of non-reciprocal devices using easy-to-integrate composite materials. The principle explores the separation of back-and-forth light paths, induced by the coupled mode asymmetry in magnetoplasmonic slot waveguides.

Magnetoplasmonic nanograting geometry enables optical nonreciprocity sign control.

We experimentally demonstrate a disruptive approach to control magnetooptical nonreciprocal effects. It has been known that the combination of a magneto-optically (MO) active substrate and extraordinary transmission (EOT) effects through deep-subwavelength nanoslits of a noble metal grating, leads to giant enhancements of the magnitude of the MO effects that would normally be obtained on just the bar substrate. This was demonstrated both in the transmission configuration, where the OET is directly observed, as well as in reflection configuration, where an increase of a transmitted power results in a decrease in reflected power.

Ultra-efficient nanoparticle trapping by integrated plasmonic dimers.

We numerically demonstrate that gold dimers coupled with a silicon-on-insulator waveguide enable an efficient plasmonic tweezing of dielectric nanobeads, having radii down to 50 nm. By means of a rigorous 3D finite difference time domain and simplified gradient force-based calculations, we investigate the effect of the gap size involved on the tweezing action. We also demonstrate that the scattering force helps the trapping in the proximity of the dimer, thanks to the establishment of light vortices.

Strong coupling and vortexes assisted slow light in plasmonic chain-SOI waveguide systems.

A strong coupling regime is demonstrated at near infrared between metallic nanoparticle chains (MNP), supporting localized surface plasmons (LSP), and dielectric waveguides (DWGs) having different core materials. MNP chains are deposited on the top of these waveguides in such a way that the two guiding structures are in direct contact with each other. The strong coupling regime implies (i) a strong interpenetration of the bare modes forming two distinct supermodes and (ii) a large power overlap up to the impossibility to distinguish the power quota inside each bare structure.

Integrated plasmonic nanotweezers for nanoparticle manipulation.

We numerically demonstrate that short gold nanoparticle chains coupled to traditional SOI waveguides allow conceiving surface plasmon-based nanotweezers. This configuration provides for jumpless control of the trapping position of a nano-object as a function of the excitation wavelength, allowing for linear repositioning. This novel feature can be captivating for the conception of compact integrated optomechanical nanoactuators.

Direct Observation of Optical Field Phase Carving in the Vicinity of Plasmonic Metasurfaces.

Plasmonic surfaces are mainly used for their optical intensity concentration properties that allow for enhancement of physical interaction like in nonlinear optics, optical sensors, or tweezers. Phase response in plasmonic resonances can also play a major role, especially in a periodic assembly of plasmonic resonators like metasurfaces. Here we show that localized surface plasmons collectively excited by a guided mode in a metallic nanostructure periodic chain present nonmonotonous phase variation along the 1D metasurface, resulting from both selective Bloch mode coupling and dipolar coupling.

Design of metallic nanoparticle gratings for filtering properties in the visible spectrum.

Plasmonic resonances in metallic nanoparticles are exploited to create efficient optical filtering functions. A finite element method is used to model metallic nanoparticle gratings. The accuracy of this method is shown by comparing numerical results with measurements on a two-dimensional grating of gold nanocylinders with an elliptic cross section.

Metallic nanoparticle chains on dielectric waveguides: coupled and uncoupled situations compared.

We investigate the optical behaviors of metallic nanoparticle (MNP) chains supporting localized surface plasmon (LSP) for different distances between particles. MNPs are excited through the fundamental TE mode of a silicon waveguide. Finite difference time domain (FDTD) calculations and optical power transmission measurements reveal three different behaviors.

Coupled mode enhanced giant magnetoplasmonics transverse Kerr effect.

We show that the enhancement of the transverse magneto-optical Kerr effect of a smooth magnetic dielectric film covered by a noble metal grating, is strongly dependent on the precise geometry of this grating. Up till now this magnetoplasmonic enhancement was solely attributed to a nonreciprocal shift of the dispersion of the surface plasmon polariton resonances at the interface with the magnetized substrate. It is demonstrated that by hybridization of surface and cavity resonances in this 1D plasmonic grating, the transverse Kerr effect can be further enhanced, extinguished or even switched in sign and that without inverting or modifying the film's magnetization.

Observation of near-field dipolar interactions involved in a metal nanoparticle chain waveguide.

We present near-field measurements of transverse plasmonic wave propagation in a chain of gold elliptical nanocylinders fed by a silicon refractive waveguide at optical telecommunication wavelengths. Eigenmode amplitude and phase imaging by apertureless scanning near-field optical microscopy allows us to measure the local out-of-plane electric field components and to reveal the exact nature of the excited localized surface plasmon resonances. Furthermore, the coupling mechanism between subsequent metal nanoparticles along the chain is experimentally analyzed by spatial Fourier transformation on the complex near-field cartography, giving a direct experimental proof of plasmonic Bloch mode propagation along array of localized surface plasmons.

Integration of short gold nanoparticles chain on SOI waveguide toward compact integrated bio-sensors.

We demonstrate the integration of short metal nanoparticle chains (L ≈700 nm) supporting localized surface plasmons in Silicon On Insulator (SOI) waveguides at telecom wavelengths. Nanoparticles are deposited on the waveguide top and excited through the evanescent field of the TE waveguide modes. Finite difference time domain calculations and waveguide transmission measurements reveal that almost all the TE mode energy can be transferred to nanoparticle chains at resonance.

Giant coupling effect between metal nanoparticle chain and optical waveguide.

We demonstrate that the optical energy carried by a TE dielectric waveguide mode can be totally transferred into a transverse plasmon mode of a coupled metal nanoparticle chain. Experiments are performed at 1.5 μm.

Magneto-optical circulator designed for operation in a uniform external magnetic field.

We propose an approach for the design of resonant cavities employed in magnetophotonic crystal (MPC) circulators and isolators. Starting from the analysis of a model circularly symmetric cavity, we show how to obtain a significant splitting of the eigenfrequencies of the two counterrotating cavity modes without introducing subdomains magnetized in opposite directions. Using the multiple-scattering method extended to handle uniaxial gyrotropic materials, we demonstrate numerically an MPC circulator working in a uniform external magnetic field.

Monitoring of Multimode Imaging Devices by use of Optical Low-Coherence Reflectometers in Reflection and Transmission Modes.

The broadband source of a high-precision optical low-coherence reflectometer is simultaneously employed in conventional reflection and transmission modes to monitor the internal properties of multimode imaging (MMI) devices. Using two carefully chosen examples, we show that this new methodology should permit precise assessment of the performance of MMI devices, including backreflection and internal reflection as well as the imbalance between output waveguides.

Coherence collapse and low-frequency fluctuations in quantum-dash based lasers emitting at 1.57 mum.

Optical feedback tolerance is experimentally investigated on a 600-mum-long quantum-dash based Fabry-Pérot laser emitting at 1.57mum. While quantum-dashes are structurally intermediate to quantum-wells and quantum-dots, the observed behaviour is distinctly like that of a quantum-well based laser but with greater stability.