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International audience; Nonlinear quadratic waveguides are key components to obtain efficient frequency conversion. In this paper we present the performances of highly multimode periodically poled lithium niobate (PPLN) ridge waveguides for high power CW SHG are presented. We report the generation of 1 W of second harmonic on the fundamental guided mode with a conversion efficiency of 56% at telecom wavelengths. A stable nonlinear process is obtained despite use of an undoped congruent LiNbO

International audience; In the framework of the Astronomical Light Optical Hybrid Analysis (ALOHA) laboratory mid-infrared (MIR) up-conversion fibred interferometer in the L band, we report on the influence of the input-stage architecture. Using an amplitude division set-up in the visible or near-infrared is a straightforward choice in most cases. In the MIR context, the results are slightly different and we show that a wavefront division set-up is needed. These in-laboratory principle experiments allow us to measure a reliable 88 per cent instrumental contrast with high flux and to obtain fringes from faint sources at 3.5 μm with a spectral bandwith of 37 nm converted to 817 nm. An equivalent limiting L-band magnitude around 3.9, equivalent to 3.0 fW nm -1, could be demonstrated on 1 m class telescopes. This opens the possibility of planning future on-sky tests at the Center for High Angular Resolution Astronomy (CHARA) array and of predicting the performance attained.

International audience; Spatial solitons or more generally self-trapped beams consist of spatially confined waves propagating without change of their transverse profile. Among the different nonlinear media allowing such behavior, we will first depict the versatility of low power photorefractive spatial solitons to realize proof of concepts and illustrate potential applications. Secondly, the recent experimental demonstration of a self-trapped wave, so-called plasmon-soliton, taking advantage of both the plasmonic and the Kerr effects will be presented.

National audience; Nous avons conçu et fabriqué des structures plasmoniques nonlinéaires planaires à base de verres de chalcogénure et d’or où nous avons pu observer pour la première fois les ondes nonlinéaires plasmons-solitons décrites théoriquement dès les années 80. Des comparaisonssatisfaisantes avec les résultats de modèles numériques spécifiques sont aussi décrites.

International audience; During the last years Optofluidic has attracted the interest of the scientific community due to its widerange of applications, from optics to biochemistry. In this field, one of the most exploited tool is thetechnology based on liquid crystals, due to their liquid nature, their optical properties and the highbiocompatibility.In this work we report our latest results on the realization of an optofluidic platform which is fullyintegrated on a lithium niobate (LiNbO3, LN) cell and allows actuating and monitoring liquid crystalsby means of light [1]. The device consists of two part: the microfluidic channel which has beenengraved on a Ti-doped LN substrate and the cover realized with a Fe-doped LN crystal. The Fe:LNcover allows reorienting liquid crystal molecules by means of the strong charge accumulations andelectric fields which can be easily created at the surface of the material by light via the photovoltaiceffect [2]. The diffused Ti:LN waveguides which cross the microfluidic channel are exploited tomonitor the time evolution of the liquid crystals reorientation, thanks to the fact that this latter inducesa change of polarization on the incoming light from the waveguide.In this way the chip is able at the same time to optically control the liquid crystals alignment inside themicrochannel and it reads the consequent light polarization alteration via an integrated waveguidessystem, thus increasing the level of integration and the full optical control of this system, paving theway for new interesting Lab-on-a-Chip and optical applications.

International audience; LiNbO3 has one of the highest quadratic nonlinear optical coefficients that makes it a material of choicefor the development of frequency conversion systems and more generally nonlinear optical functions.This crystal can be periodically poled (PPLN) to allow quasi‐phase matching for various combinationsof wavelengths mixing in its wide transparency window (0.4‐5 μm). In addition, efficient nonlinearconversion can be reached even with moderate power CW beams taking advantage of the lightconfinement provided by LiNbO3‐based optical waveguides. However, waveguides made byconventional fabrication techniques such as titanium in‐diffusion or proton exchange still suffer fromunstable behavior due to photorefractive optical damage especially when visible wavelengths areconcerned. In this study, we present recent developments of ridge PPLN waveguides with promisingcharacteristics even when operating at high average power.More specifically, the design, fabrication and characterization of nonlinear PPLN waveguides forsecond harmonic generation (SHG) of telecommunication wavelengths are presented. Fabrication isbased on wafer bonding, grinding‐polishing steps and carving with use of a precision dicing saw. Thecomponents show efficient SHG with normalized conversion over 200%/W. The componentsperformances will be presented along with their long‐term stability when pumped with Watt‐leveloptical signals. Optical damage threshold of the input face is also investigated to determine themaximum usable power. Undoped and MgO doped LiNbO3 are considered. We will also emphasizethe specificity of the ridge waveguides that allows stable frequency conversion at high power. Theperspectives offered by this specific waveguide geometry will also be tackled.

International audience; Merging the fields of plasmonics and nonlinear optics authorizes a variety of fascinating and original physicalphenomena. In this work, we specifically study the combination of the strong light confinement ability of surfaceplasmon polaritons (SPP) with the beam self-trapping effect in a nonlinear optical Kerr medium. Although this idea ofplasmon-soliton has been the subject of numerous theoretical papers [1], up to now, no experimental evidence had beenrevealed. In the present study, a proper architecture has been designed and fabricated allowing the first experimentalobservation of hybrid coupling between spatial solitons and SPP.To be able to trigger the nonlinearity at moderate light power and simultaneously allow propagation over severalmillimeters, a metal-dielectric structure was first designed. It consists of a four–layer planar geometry made of a Kerrdielectric layer placed on a lower refractive index substrate and covered with a thin dielectric layer followed by a metallicfilm. Performed numerical simulations show that the designed planar waveguide exhibits an enhanced Kerr self-focusingfor the TM0 mode thanks to the plasmonic effect.The experimental analysis consists in injecting a typical 4 × 30 μm2 (FWHM) elliptical beam at 1.55μm from afemtosecond laser into the 5mm long waveguide. The output beam distribution evolution is then monitored versus inputlight intensity. Figure 1 shows the large trapping enhancement observed for a TM mode in presence of the plasmonicstructure (Fig. 1d,e) compared to configurations (Fig. 1b,c and Fig. 1f,g) where plasmonic effect is absent. For an inputintensity of 1.2 GW/cm² the beam is self-confined to a 12μm FWHM (Fig. 1e) while the FWHM is twice (Fig. 1c,g)without plasmonic effect. The proposed plasmonic structure definitely exposes an enhanced self-focusing nonlinearity.The strong light confinement is due to the presence of the hybrid coupling between a plasmon and a soliton waves.Different configurations have also been tested that unambiguously reveal this plasmon-soliton coupling.

International audience; We report the experimental observation of plasmon-soliton waves. The demonstration isperformed in a chalcogenide-based four-layer planar geometry. It reveals a plasmon-enhanced Kerr selffocusingundergone by a TM polarized beam propagating inside the structure.

National audience; While plasmonics has seen numerous striking experimental results during the last decade, there is only very few dealing with nonlinear integrated plasmonics. This last research topic addresses photonic devices in which waveguide aspects are predominant and nonlineareffects emerges from bulk term. Our current work belongs to this difficult but promising topic. We have obtained the first experimental proof of the coupling between a plasmon and a spatial soliton. This demonstration have been realized in a layered planar structure where the nonlinear layer is made of a specific chalcogenide glass ensuring both a high nonlinear coefficient, a low two-photon absorption, and a relatively high power damage threshold. In its plasmonic part, the chalcogenide layer is separated from the 32 nm thick gold layer by a 10 nm thick silica layer whom the thickness was optimized by modal numerical simulations in order to ensure a high effective nonlinearity of the plasmonic structure. Our experimental results reveal a strong reinforcement of the self-focusing of the incident beam only when it passes through the plasmonic part of the structure. This effect occurs when TM polarized waves are launched while no reinforcement is observed when TE polarized waves are considered. This is one of the signatures of the plasmon-soliton coupling. Power dependency of the recorded spatial profiles has also been studied together with the impact of the localization of the plasmonic structure relatively to the input facet of the light beam. In order to get a better understanding of these phenomena, we have build a spatial nonlinear propagation model taking into account two spatial dimensions and the different field profiles along the full structure (with/without the gold layer). We get a good agreement between the experimental data and the numerical results.

International audience