20 research outputs found
Spin-Orbit coupling in nanophotonics. Application to unidirectionnal excitation of plasmonics guided modes and nanométrics opto-magnetisation generation controled by the polarisation state of light
No full textCette thèse porte sur la manipulation du moment angulaire de la lumière à l'échelle sub-micronique. Le moment angulaire total de la lumière est composé d'une partie de spin, relié au degré de liberté de polarisation circulaire de la lumière, et d'une partie orbitale, relié au degré de libertés spatiaux de la lumière que sont sa direction de propagation (locale et globale) et sa distribution spatiale d'intensité. Le couplage spin-orbite existant entre ces deux contributions permet alors de manipuler les degrés de libertés spatiaux de la lumière par un simple contrôle de son état de polarisation circulaire. Dans cette thèse, nous avons étudié et exploité ce couplage à l'échelle sub-micronique dans deux nouveaux phénomènes que nous avons mis en évidence. Le premier met à profit ce couplage pour permettre d'exciter de manière unidirectionnelle des modes plasmoniques guidés. Une étude complète (numérique, expérimentale et analytique) de ce phénomène nouveau, basé sur un couplage entre le moment de spin du photon incident et le moment orbital extrinsèque des modes plasmoniques guidés dans la courbure d'un guide, est présentée. La deuxième étude présente une voie pour tirer parti du transfert de moment orbital de la lumière à un gaz d'électrons libres dans un métal afin de générer et contrôler le sens et la géométries de boucles de courants sub-microniques dans des structures métalliques. Ce contrôle permettrait la génération d'optomaimants nanométriques, entièrement contrôlés par la lumière, pouvant être modulés aux fréquences optiques. Ce travail a été soutenu par le LABEX Action.This thesis focuses on the manipulation of the angular momentum of light at the nanoscale.The total angular momentum of light is composed of a spin component, connected to the polarization degree of freedom of light, and an orbital component, related to the spatial degrees of freedom of the light which are its propagation direction (local and global) and its intensity distribution. The spin-orbit coupling between these two contributions allows the control of the spatial degrees of freedom of light by a simple manipulation of its circular polarization state. In this thesis, we have studied and applied this coupling at the nanoscale anbd we have highlighted two new phenomenas. The first one takes part of this coupling to allows unidirectional excitation of plasmonic guided modes. A complete study (numerical, experimental and analytical) of this new phenomenon, based on a coupling between the spin of the incident photon and the extrinsic orbital momentum of the plasmonic guided modes within the curvature of a waveguide, is presented. The second study propose a way to benefit from the transfer of the angular momentum of light to the free electrons gas in a metal to generate and control the direction and the geometry of nanoscale current loops in metallic structures. this control would at optical frequencies. This work was supported by the LABEX Action
Etudes du couplage spin-orbite en nano-photonique. applications à l'excitation unidirectionnelle de modes plasmoniques guidés et à la génération d'opto-aimants nanométriques contrôlables par l'état de polarisation de la lumière
No full textThis thesis focuses on the manipulation of the angular momentum of light at the nanoscale.The total angular momentum of light is composed of a spin component, connected to the polarization degree of freedom of light, and an orbital component, related to the spatial degrees of freedom of the light which are its propagation direction (local and global) and its intensity distribution. The spin-orbit coupling between these two contributions allows the control of the spatial degrees of freedom of light by a simple manipulation of its circular polarization state. In this thesis, we have studied and applied this coupling at the nanoscale anbd we have highlighted two new phenomenas. The first one takes part of this coupling to allows unidirectional excitation of plasmonic guided modes. A complete study (numerical, experimental and analytical) of this new phenomenon, based on a coupling between the spin of the incident photon and the extrinsic orbital momentum of the plasmonic guided modes within the curvature of a waveguide, is presented. The second study propose a way to benefit from the transfer of the angular momentum of light to the free electrons gas in a metal to generate and control the direction and the geometry of nanoscale current loops in metallic structures. this control would at optical frequencies. This work was supported by the LABEX Action.Cette thèse porte sur la manipulation du moment angulaire de la lumière à l'échelle sub-micronique. Le moment angulaire total de la lumière est composé d'une partie de spin, relié au degré de liberté de polarisation circulaire de la lumière, et d'une partie orbitale, relié au degré de libertés spatiaux de la lumière que sont sa direction de propagation (locale et globale) et sa distribution spatiale d'intensité. Le couplage spin-orbite existant entre ces deux contributions permet alors de manipuler les degrés de libertés spatiaux de la lumière par un simple contrôle de son état de polarisation circulaire. Dans cette thèse, nous avons étudié et exploité ce couplage à l'échelle sub-micronique dans deux nouveaux phénomènes que nous avons mis en évidence. Le premier met à profit ce couplage pour permettre d'exciter de manière unidirectionnelle des modes plasmoniques guidés. Une étude complète (numérique, expérimentale et analytique) de ce phénomène nouveau, basé sur un couplage entre le moment de spin du photon incident et le moment orbital extrinsèque des modes plasmoniques guidés dans la courbure d'un guide, est présentée. La deuxième étude présente une voie pour tirer parti du transfert de moment orbital de la lumière à un gaz d'électrons libres dans un métal afin de générer et contrôler le sens et la géométries de boucles de courants sub-microniques dans des structures métalliques. Ce contrôle permettrait la génération d'optomaimants nanométriques, entièrement contrôlés par la lumière, pouvant être modulés aux fréquences optiques. Ce travail a été soutenu par le LABEX Action
Tunable Optomagnets in Diamagnetic Thin Metal Layers and Plasmonic Nano-Antennas
No full textInternational audience<h1> </h1&g
Unidirectional sub-diffraction waveguiding based on optical spin-orbit coupling in subwavelength plasmonic waveguides
No full textInternational audienceSubwavelength plasmonic waveguides show the unique ability of strongly localizing (down to the nanoscale) and guiding light. These structures are intrinsically two-way optical communication channels, providing two opposite light-propagation directions. As a consequence, when light is coupled to these planar integrated devices directly from the top (or bottom) surface using strongly focused beams, it is equally shared into the two opposite propagation directions. Here, we show that symmetry can be broken over a broad spectral bandwidth by using incident circularly polarized light, on the basis of a spin–orbital angular momentum transfer directly within waveguide bends. We predict that up to 94% of the incoupled light is directed into a single propagation channel of a gap plasmon waveguide. Unidirectional propagation of strongly localized optical energy, far beyond the diffraction limit, becomes switchable by polarization, with no need of intermediate nano-antennas/scatterers as light directors. This study may open new perspectives in a large panel of scientific domains, such as nanophotonic circuitry, routing and sorting, optical nanosensing, and nano-optical trapping and manipulation
Couplage spin-orbite optique dans des guides d’ondes plasmoniques sub-longueurs d'ondes : excitation unidirectionnelle de modes guidés à l’échelle nanométrique
No full textNational audience 
Directing nanoscale optical flows by coupling photon spin to plasmon extrinsic angular momentum
No full textInternational audienceAs any physical particle or object, light undergoing a circular trajectory features a constant extrinsic angular momentum. Within strong curvatures, this angular momentum can match the spin momentum of a photon, thus providing the opportunity of a strong spin-orbit interaction. Using this effect, we demonstrate tunable symmetry breaking in the coupling of light into a curved nanoscale plasmonic waveguide. The helicity of the impinging optical wave controls the power distribution between the two counter-propagating subwavelength guided modes including unidirectional waveguiding. We found experimentally that up to 95% of the incoupled light can be selectively directed into one of the two propagation directions of a nanoscale waveguide. This approach offers new degrees of freedom in the manipulation of subdiffraction optical modes and thus appealing new prospects for the development of advanced, deeply subwavelength optical functionalities
Optically induced magnetic field in plasmonic nanostructures
No full textInternational audienceWe provide a spin and orbital angular momentum representation of the inverse Faraday effect in a metal. We analytically show the role of the spin and orbital angular momenta of light (SAM and OAM, respectively), as well as the spin-orbit interaction (SOI), in the generation of an optoinduced magnetization. We also show that resonances in plasmonic nanoantennas enhance and confine the IFE on the nanoscale, thereby leading to static magnetic fields directly applicable in a vast application domain including all-optical magnetization switching and spin-wave excitation
Optoinduced magnetization from the spin and orbital angular momenta of light
No full textInternational audienceWe provide a spin and orbital angular momentum representation of the inverse Faraday effect in a metal. We analytically show the role of the spin and orbital angular momenta of light (SAM and OAM, respectively), as well as the spin-orbit interaction (SOI), in the generation of an optoinduced magnetization. We also show that resonances in plasmonic nanoantennas enhance and confine the IFE on the nanoscale, thereby leading to static magnetic fields directly applicable in a vast application domain including all-optical magnetization switching and spin-wave excitation
Inverse Faraday effect from the orbital angular momentum of light
No full textInternational audienceIt is usually admitted that the inverse Faraday effect (IFE) originates from the spin angular momentum (SAM) of light. In this paper, we show that part of the IFE in a metal is induced by the orbital angular momentum (OAM) of light. On the basis of a hydrodynamic model of the conduction electron gas, we describe the dependence of the IFE on the spin and orbital angular momenta as well as spin-orbit interaction in a nonparaxial light beam. We also numerically quantify the relative contributions of the SAM and OAM of light to the IFE in a thin gold film illuminated by different focused beams carrying SAM and/or OAM. The OAM of light provides an additional degree of freedom in the control of the IFE and resulting optomagnetic field, thus potentially impacting various research fields, including all-optical magnetization switching and spin-wave excitation
Optomagnetism in plasmonic nanostructures
No full textInternational audienceOptically-induced magnetism has drawn considerable interest in the past years for its ability to speed up magnetic processes. For example, static magnetic fields have been demonstrated to be generated in non-magnetic plasmonic (gold) nanoparticles and nano-apertures. Using a simplified hydrodynamic model of the free electron gas of metal, we theoretically investigate the IFE and resulting optomagnetism in a thin gold film as well as in axis-symmetric plasmonic nanostructures under illumination with various focused light. The resulting static magnetic field is found to be maximum and dramatically confined at the corners and edges of the plasmonic structures, which reveals the ability of metallic discontinuities to concentrate and tailor static magnetic fields on the nanoscale. Plasmonics can thus generate and tune static magnetic fields on the nanoscale, potentially impacting small-scale magnetic tweezing and sensing as well as the generation of magneto-optical effects and spin-waves
