B. Dagens

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.

Experimental demonstration of anomalous nonreciprocal optical response of 1D periodic magnetoplasmonic nanostructures.

In this paper we analyze the optical and transversal magnetooptical (MO) response of magnetoplasmonic (MP) nanostructures. The MP structure is a 1D periodic gold grating fabricated by lift-off technique on the MO dielectric substrate (Bi-substituted yttrium iron garnet BixY3−xFe5O12). Following our recent theoretical work (Opt. Express 21, pp. 2174121755, Sep 2013.), we confirm here experimentally the predicted dependence of the MO response on the geometry of the grating, that is directly attributed to the anticrossing behavior of the Fabry-Perot (FP) resonance in the grating’s slits and the surface plasmon resonances (SPPs) at its interfaces. The experimental results were achieved by Mueller matrix spectroscopic ellipsometry. Observed fine tuning of the transverse magneto-optic Kerr opens up new possibilities for the design of compact nonreciprocal devices.

Compact integrated optical isolation based on extraordinary dichroic transmission through a magnetoplasmonic waveguide grating

Using rigorous magneto-optical waveguide modelling, we have calculated the dichroic transmission of the fundamental TM waveguide mode through a magnetoplasmonic waveguide grating. The ferromagnetic metallic grating material is a CoFe alloy that is magnetized parallel to the grating. When deposited on top of a standard III-V waveguide with a thin top cladding layer and thus placed in the evanescent tail of the guided TM ground mode, it induces both plasmonic and magneto-optic effects in the transmission of this waveguide grating. Due to the direction of the magnetization - perpendicular to the light propagation and parallel to the waveguide layer interfaces - the integrated transverse magnetooptic Kerr effect induces non-reciprocal dichroic transmission for the guided TM light. We have numerically studied the TM ground mode dichroism (for a telecom wavelength of 1300nm) as a function of the cladding layer thickness and the grating parameters, namely its duty cycle, period and thickness. This study has revealed that there exist clear grating designs where the dichroic transmission is resonantly enhanced as compared to the case where the ferromagnetic metal is a continuous film. A detailed study of the field maps associated to these points reveals that the guided TM ground mode resonantly couples to a vertical cavity plasmonic resonance in the air slots of the CoFe grating. This behaviour is reminiscent of extraordinary optical transmission but here in an integrated non-reciprocal version. We have previously reported experimentally strong integrated and forward transparent optical isolation based on this TM dichroism but using a continuous film [1,2]. The present design study indicates that the extraordinary magnetoplasmonic effects taking place in a properly designed CoFe grating improves the performance of this device by at least a factor 4.

Modelling of magneto photonic waveguide using RCWA

Magneto photonic crystals exhibit unique combination of magneto-optical nonreciprocity and resonant behavior originating from periodic structure. Modeling of magneto photonic structures requires inclusion of magnetic induced anisotropy and description of medium using a permittivity tensor. On the other hand, differential theory of periodic gratings based on Fourier expansion of permittivity tensor and electromagnetic field is recently frequently applied. In this paper we propose an approach of effective propagation constant calculation from scattering matrix of the waveguide consisting of the anisotropic magneto-optical lamellar grating. The structure is modeled using Rigorous Coupled Wave Analysis (RCWA) extended by Fourier factorization method. The approach is applied to optimize parameters of integrated magneto-optic waveguide isolator with lamellar grating from magneto-optic medium at transverse geometry.

Integrated plasmonic nanotweezers: Toward the manipulation of nanoobjects

In this paper, we present the numerical conception of a surface plasmon-based nanotweezers obtained by coupling a short nanoparticle chain to a traditional SOI waveguide. In particular, we detail on simplified calculation scheme, based on the estimation of the gradient force, able to ease the analysis when the refractive index of the tweezed particles is similar to that of the background. Results suggest the possibility of controlling the position where the trapping occurs along the chain as a function of the wavelength. This may be crucial for achieving the possibility of manipulating objects in the nanoscale by means of integrated devices.

Integrated plasmonic tweezer for linear repositioning of nanometric objects

Plasmonic nanoparticles chains coupled to traditional SOI waveguides allow for nanoobjects trapping and jumpless linear repositioning. This innovative feature is here numerically detailed. This may be extremely captivating for the conception of integrated optomechanical nanoactuators.

Integrated magnetoplasmonic nanostructures for non-reciprocal optical devices

We have numerically shown that when a magneto-optical bismuth iron garnet waveguide is coupled to a gold grating on its top, surface plasmon polaritons can strongly enhance transverse magneto-optical Kerr effect, and thus non-reciprocal transmission.

Magnetoplasmonic waveguiding structure with nonreciprocal dispersion of guided TM modes

In this paper we present our study of waveguiding structure with nonreciprocal dispersion of guided modes. The considered structure is based on the Silicon waveguide core and the plasmonic (gold) 1D periodic grating. The waveguide and the grating are separated by low refractive index layer (SiO2). The structure operates as follows. The evanescent field of the guided mode is used for the excitation of the surface plasmon polaritons (SPPs) at the top side of the grating. To achieve non-reciprocity the magneto-optical dielectric garnet is assumed to be on the top of the grating. The presence of the transversal magnetization in the garnet leads to the nonreciprocal shift of the SPP. Together with the evanescent coupling of guided modes this leads to the nonreciprocal dispersion of guided mode. The grating period is varied to achieve coupling of grating’s resonances with the waveguide evanescent field and therefore possible enhancement of the nonreciprocal response.

Bloch mode spatial harmonic decomposition in integrated localized surface plasmon chain

We consider a gold nanoparticle chain integrated on a dielectric waveguide. With appropriate geometrical parameters, such a chain behaves as a waveguide. We show that the spatial harmonics generated in the sub-wavelength periodic structure can be locally separated or extracted. This is done by playing with the phase matching condition of the coupling with the dielectric waveguide: only the fundamental component is locally cancelled in the periodic structure, resulting in a non-monotone phase evolution along the structure. Additionnally we show that the analysis of spatial harmonics allows extracting more information on the localized surface plasmon mode generation.

Light propagation in metallic nanoparticle chains on SOI waveguide

In this work, we demonstrate successful interfacing between metallic nanoparticle (MNP) chain supporting localized surface plasmons (LSP) and silicon-on-insulator (SOI) waveguides. We show that the optical energy carried by a TE SOI waveguide mode at telecom wavelengths can be efficiently transferred into MNP chains deposited on the waveguide top, whatever the number of metallic particles (from 5 to 50). Especially in short chains, most of the energy can be transferred into the fourth or fifth MNP of the chains. Predictions from theoretical models are fully corroborated by transmission and near-field measurements.