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 ∼2µm and ∼50fs, respectively. Moreover, the function of spatiotemporal differentiation is demonstrated with input flat-top pulse fields. The proposed optical differentiator has potential applications in ultra-compact real-time optical multifunctional computing systems and parallel signal processing.

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. We show numerically that such a structure combined with suitable absorbers gives more than a 18 dB isolation ratio on several tens of nanometers bandwidth, with 2 dB insertion losses.

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. Additionally, since the system involves LSPs, (i) such a strong coupling occurs on a broad band and (ii) the peculiar vortex-like propagation mechanism of the optical power, supported by the MNP chain, leads to a regime where the light is slowed down over a wide wavelength range. Finally, the strong coupling allows the formation of guided supermodes in regions where the bare modes cannot be both guided at the same time. In other words, very high k modes can then be propagated in a dielectric photonic circuit thanks to hybridisation, leading to extremely concentrated propagating wave. Experimental work gives indirect proof of strong coupling regime whatever the waveguide core indexes.

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.

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. For short distances between particles, dipolar coupling occurs, and the MNP chain behaves as a waveguide. For the longest distances, nanoparticles are uncoupled, and the MNP chain acts as a LSP Bragg grating. Finally, for intermediate distances, we observe one behavior at a time, i.e. dipolar coupling or LSP Bragg reflection. There is only a small range of wavelengths within which both behaviors can coexist.

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. It is also shown that the transmission spectrum is very sensitive to the molecular environment of nanoparticles, thus opening the way towards ultra-compact sensors in guided plasmonics on SOI. An experimental demonstration is reported with octadecanthiol molecules for a detection volume as small as 0.26 attoliter.

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. Mode coupling occurs through the evanescent field of the dielectric waveguide mode. Giant coupling effects are evidenced from record coupling lengths as short as ~560 nm. This result opens the way to nanometer scale devices based on localized plasmons in photonic integrated circuits.

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.