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Ceramic resonators offer new possibilities for magnetic resonance microscopy

Systematic Analysis of the Improvements in Magnetic Resonance Microscopy with Ferroelectric Composite Ceramics

Magnetic Resonance Microscopy enables imaging of samples in the millimetre domain with sub-micrometric resolution. We developed a new type of probe made of ceramic material allowing to produce images with resolution twice higher than with conventional metal probes.


In magnetic resonance microscopy (MRM), an imaging modality that focuses on imaging of samples of a few millimetres size, the commonly used probe is a solenoid coil made of copper wire. When fed by an electrical current, it produces a magnetic field which is essential to obtain an image. Doing so, an electric field is also generated within the biological sample. The latter usually being conductive, it induces dielectric losses and represents a source of noise. At fixed acquisition time, this phenomenon intrinsically limits the achievable signal-to-noise ratio (SNR) and, therefore, the resolution.
In this framework, several research works have evoked and demonstrated the potential of ceramic probes to overcome this limitation at several static magnetic field intensities B0. These probes exploit the first transverse electric mode of an annular-ring dielectric resonator which is simply excited by a small current loop. Among the special features of this resonator are its axial magnetic field, similar to that of the reference probe, together with an insignificant electric field. The resonator properties are chosen so that the mode of interest resonates at a frequency close to the Larmor frequency of protons at the given B0 field intensity. At 17 T, the studied resonator had to be made of a ceramic with relative permittivity 530 while ensuring a low intrinsic loss level within the dielectric material to avoid additional noise during the MRI acquisition. These constraints – high permittivity and low losses – could be relieved with a customised new ferroelectric ceramic material containing magnesium additives.
A semi-analytical model was set up to propose an estimation of the achievable SNR. This allowed to compare the performances of the ceramic probe with the solenoid coil as a parametric estimation problem depending on the electromagnetic properties of both the ferroelectric material and the sample. Numerical simulations validated this approach in the studied configuration that was also experimentally tested for imaging of vegetal sample (ilex aquifolium) at 17 T.
Experimental investigations in MRI confirmed predictions of the theoretical and numerical studies, that is an SNR gain of around 2 in favour of the ceramic probe over the solenoid coil. This was explained by the very limited electric field – sample interaction in the case of ceramic probe, thanks to the electric field distribution presenting remarkably low values in the sample region.
This research paves the way for a novel approach of microscopy probes development. Optimized designs of ceramic probes are enabled by the opportunity to elaborate customized ferroelectric materials. For a sample with given dimensions and properties, it has become possible to make an informed decision about choosing a solenoid coil or a ceramic probe in order to reach the best image resolution.

Partner :
- CEA NEUROSPIN - Read the article of CEA Joliot Curie
- ITMO University

Reference : M. A.C. Moussu, L. Ciobanu, S. Kurdjumov, E. Nenasheva, B. Djemai, M. Dubois, A. Webb, S. Enoch, P. Belov, R. Abdeddaim, S. Glybovski, “Systematic Analysis of the Improvements in Magnetic Resonance Microscopy with Ferroelectric Composite Ceramics”, accepted for publication in Advanced Materials
Version of Record online : 17 May 2019

- CNRS INSIS also published this information in his newsletter "En direct des labos" under the title "Une antenne en céramique améliore la qualité des images par résonance magnétique"

Contacts :
Marine Moussu, Institut Fresnel - UMR7249, Marseille -
Luisa Ciobanu, CEA Neurospin, Gif-sur-Ivette
Stanislav Glybovski, ITMO University, Saint-Pétersbourg

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement n°736937

Toward an ever-more efficient collaboration between academia and industry

Angularly tunable bandpass filter : design, fabrication and characterization

Thin-Film filters offer a wide range of applications from earth observation to biophotonics. They are generally hidden components in systems but play a key role in improving the performances of optical instruments. Recent collaborative efforts between the Thin-Film research team of Institut Fresnel and Bühler company have permitted to demonstrate new high performance angularly tunable filter for near-infrared range. This filter, composed with a total of about 300 layers has been successfully designed and fabricated on a Bühler HELIOS machine (Plasma Assisted Reactive Magnetron Sputtering) combined with Optical Monitoring System. A custom dedicated measurement setup has also been developed in order to measure the performances of this high performance optical filter. Close to theoretical performances of this class of filter has been demonstrated. These results not only highlight the capability to develop complex filters within the Espace Photonique platform at Institut Fresnel, but also a very fruitful collaboration between Academia (Institut Fresnel) and industry (Bühler company) for the development of optical components with more and more ultimate performances.

Image : Left – Measured and theoretical transmission spectral performances of the fabricated filter / Right – Illustration of optical interference filters

Reference :
J. Lumeau, F. Lemarchand, T. Begou, D. Arhilger, and H. Hagedorn, "Angularly tunable bandpass filter : design, fabrication and characterization", Optics Letters 44(7), 1829-1832 (2019) – Editors’ Pick.

More Informations :
- on our Photonic Space, "Plateforme Technologique d’Aix Marseille Université"
- on our partner BUHLER

Contact : Julien Lumeau

Imaging energy transfer between dipole antennas inside a photonic cavity

Photonic cavities provide a way to enhance interactions between dipoles. A new theoretical and experimental analysis provides design rules for optimizing this enhancement at microwave frequencies.

Light can be trapped inside a cavity made by two mirrors, thus concentrating the light intensity and enhancing interactions between light and matter. Among the different applications of these photonic cavities, much attention is now focused on their ability to control the energy exchange between quantum emitters such as atoms, molecules, and quantum dots. Attempts to improve this exchange have been hampered by experimental difficulties in controlling the positions, orientations, and spectra of the emitter’s dipoles. Here, we thoroughly characterize dipole-dipole energy transfer inside a photonic cavity, and provide design rules for cavity-enhanced applications.

At the nanoscale, the energy transfer between two light-sensitive elements is primarily governed by a dipole-dipole interaction described by a mathematical formalism known as Förster resonance energy transfer (FRET). We developed a general methodology to analyze FRET at microwave frequencies. While previous research has focused on optical frequencies, microwave experiments allow us to measure energy transfer with a high degree of control over dipole orientation and position. We then test our framework by investigating the energy transfer between two microwave antennas inside a photonic cavity and derived the conditions that enhance the transfer.

Our methodology bridges the gap between quantum electrodynamics and microwave engineering descriptions of dipole-dipole interactions. Beyond the conceptual interest, this approach provides a practical tool to quantitatively characterize photonic devices with an enhanced dipole-dipole interaction and can be readily applied to map energy transfer inside complex photonic systems at ultrahigh resolutions.

Direct measurement of the energy transfer between dipole antennas inside a photonic cavity.

This research was conducted within the context of the International Associated Laboratory “ALPhFA : Associated Laboratory for Photonics between France and Australia”, and has received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 736937, from the Agence Nationale de la Recherche (ANR) under grant agreement ANR-17-CE09-0026-01, and from Excellence Initiative of Aix-Marseille University - A*MIDEX, a French “Investissements d’Avenir” program.

- Read the article on the CNRS - INSIS website  :
« Une cartographie des transferts d’énergie dans les cavités optiques radiofréquences »

Reference :
K. Rustomji, M. Dubois, B. Kuhlmey, C. M. de Sterke, S. Enoch, R. Abdeddaim, J. Wenger, “Direct imaging of the energy transfer enhancement between two dipoles in a photonic cavity”, Physical Review X , march 2019

Contact : Redha Abdeddaim, Stefan Enoch and Jérôme Wenger

Metamaterial enhanced ultra-high field magnetic resonance imaging

A team of physicists from our Lab, the Langevin Institute and the CEA NeuroSpin recently published in the prestigious Physics Review X their work on Metamaterials to improve the quality of ultra-high field magnetic resonance imaging (MRI 7T).

Novel metamaterial approach improves image quality of magnetic resonance imaging obtained with ultra-high magnetic field scanners. This approach helps to advance these cutting-edge equipment towards global clinical applications for faster and more precise medical imaging.

Since its discovery in the early 70’s, MRI scanners have become one of the most efficient diagnostic tools available for physicians. Also, over time, their magnetic field strength has been steadily increased to enhance the Signal to Noise Ratio yielding a radical improvement of spatial and temporal resolution as well as biological contrast. On the other hand, such a strategy induces an increasing working frequency of the radio-frequency (RF) excitation field. It becomes problematic as human body size becomes non negligible compared with the associated wavelength. This induces strong RF field inhomogeneities leading to major losses in contrast or shadowing on the images and strongly limits the clinical application of High-Field MRI scanners.

The M-Cube project breakthrough is based on electromagnetic metamaterials offering an unprecedented ability to tailor RF field inside MRI coils. The interaction of electromagnetic modes within the metamaterial enables the access to the so-called Kerker scattering conditions leading to either a 3-fold enhancement of the local RF field or to be used as a local RF shield in order to protect over exposed body areas

Reference : “Kerker effect in ultrahigh-field magnetic resonance imaging” ; Marc Dubois, Lisa Leroi, Zo Raolison, Redha Abdeddaim, Tryfon Antonakakis, Julien de Rosny, Alexandre Vignaud, Pierre Sabouroux, Elodie Georget, Benoit Larrat, Gérard Tayeb, Nicolas Bonod, Alexis Amadon, Franck Mauconduit, Cyril Poupon, Denis Le Bihan, and Stefan Enoch ; Phys. Rev. X


Labs concerned by this article :
- Institut Fresnel
- Institut Langevin
- CEA NeuroSpin
- Multiwave

Contact Researcher : Redha Abdeddaim, Stefan Enoch et Marc Dubois

This work is part of the H2020 FET-Open M-Cube project. It has received funding from the European Union’s Horizon 2020 Research and Innovation program under Grant Agreement No 736937


Correlated Disordered Plasmonic Nanostructures Arrays for Augmented Reality

The optical properties of metallic nanoparticles are exploited to design transparent surfaces used in innovative display devices. The subwavelength characteristic dimensions of nanoparticles are optimized to obtain a reflection efficiency at the desired color without altering the overall transparency quality of the substrate. Their spatial arrangement is chosen to eliminate non-specular diffraction, regardless of their spatial density. The responses of different silver nanoparticle arrangements (periodic or correlated-disordered arrangements, different spatial densities and nanoparticle dimensions) are analyzed numerically and experimentally by measuring the reflectance and transmittance spectra in the visible. It is shown that correlated-disordered arrangements decrease the effect of non-specular diffraction occurring at low spatial densities of nanoparticles. This low density of nanoparticles makes it possible to obtain a better overall transparency of the device. These configurations are promising for the design of innovative display devices of interest to the transport industry (e. g. head-up vision in the automobile) or "augmented reality" applications.

Partners :
- Centre de Nanosciences et de Nanotechnologies, CNRS / Université Paris-Sud
- Institut Fresnel, CNRS / Université d’Aix-Marseille / Centrale Marseille
- Groupe PSA

Reference : "Correlated Disordered Plasmonic Nanostructures Arrays for Augmented Reality", Hervé Bertin, Yoann Brûlé, Giovanni Magno, Thomas Lopez, Philippe Gogol, Laetitia Pradere, Boris Gralak, David Barat, Guillaume Demésy and Beatrice Dagens. ACS Photonics, 2018, 5 (7), pp 2661–2668,

DOI : 10.1021/acsphotonics.8b00168

Keywords : nanosciences, optics, metasurface, augmented reality

Contact Institut Fresnel : Boris Gralak or Guillaume Demésy

Contact Centre de nanosciences et de nanotechnologies : Béatrice Dagens

Other publications on this subject :
La lettre de l’innovation du CNRS, n°45, Ajuster la réflectance d’un verre tout en préservant sa qualité de transparence

Long-range correlations measured between water molecules

The configuration of water molecules in an aqueous solution transitions from a long-range stacked pattern to a short-range radial pattern when salt is added.

In this article, published in the journal Physical Review Letters, Julien Duboisset (Institut Fresnel, Marseille) and Pierre-François Brevet (Institut Lumière Matière, Lyon) describe nonlinear optical experiments in the liquid phase determining the orientation correlation of water molecules. These experiments show that water molecules are organized over much greater distances than is usually accepted. They demonstrate indeed that the molecules are orientationnally arranged over distances of several tens of nanometers in a spatial azimuthal distribution. This work also show that when salt is added, a transition occurs where water molecules abruptly change their initial organisation into a short scale radial distribution centered on the salt ions.
This discovery, published in the journal Physical Review Letters and selected by the editor as a highlight, challenges the classic view of liquids and their organization of molecules at the nanoscale.

Left : Illustration of long range correlations between water molecules. In red, water molecules, in blue salts.
Right : lenght of correlations as function of salt concentration.

Reference :
Salt-induced Long-to-Short Range Orientational Transition in Water, Julien Duboisset and Pierre-François Brevet, Phys. Rev. Lett. 120, 263001 (2018) - Consulter l’article on-line

Contact Researchers :

- Julien Duboisset, Institut Fresnel - UMR7249, Aix Marseille Univ, CNRS, Centrale Marseille, 13013 Marseille, France (INSIS)
Tél : 04 91 28 80 49

- Pierre-François Brevet, Institut Lumière Matière – UMR 5306, Université Lyon1, CNRS, 69622 Villeurbanne, France (INP)

"Enhancing magnetic light emission with all-dialectric optical nanoantennas"

Article published in Nano Letters, september 2018

Des chercheurs ont élaboré une nanostructure capable d’accroître le champ magnétique d’une onde lumineuse, ouvrant la possibilité d’observer l’interaction entre cette composante magnétique de la lumière, et la matière.

Ces travaux ont été menés par des physiciens de l’Institut des nanosciences de Paris (CNRS/Sorbonne Université) et l’Institut de Ciencies Fotoniques, en collaboration avec :
- le Laboratoire de physique et d’études des matériaux (CNRS/ESPCI Paris/Sorbonne Université),
- l’IBM Almaden Research Center (USA),
- l’Institut Fresnel (CNRS/AMU/Centrale Marseille),
- le Laboratoire de physique de la matière condensée (CNRS/X
- l’Institut Langevin (CNRS/ESPCI Paris/Univ. Paris Diderot/Inserm/Sorbonne Université)

Reference :
Enhancing magnetic light emission with all-dielectric optical nanoantennas
M. Sanz-Paz, C. Ernandes, J. Uriel Esparza, G. W. Burr, N. F. van Hulst, A. Maitre, L. Aigouy, T. Gacoin, N. Bonod, M. F. Garcia-Parajo , S. Bidault et M. Mivelle,
Nano Letters (2018)

Développement d’un technique d’imagerie moléculaire des tissus pour des applications médicales "SRGold"
Projet de maturation de la SATT Sud-Est en collaboration avec le CNRS et HORIBA France

Grâce à une avancée majeure en microscopie Raman stimulée, des chercheurs de l’équipe MOSAIC proposent désormais de réaliser en quelques minutes une image des molécules présentes dans un échantillon biologique. Les perspectives sont donc de pouvoir produire une nouvelle génération d’instruments hospitaliers afin de mieux identifier les tissus cancéreux.

La technique de Spectroscopie Raman Stimulée (SRS) permet de localiser dans un échantillon certaines espèces chimiques, identifiées par le type de liaisons qu’elles contiennent. Cette méthode appliquée à la microscopie de tissus biologiques permettra notamment de distinguer les tissus qui ont un caractère cancéreux. Or, les signaux Raman des molécules recherchées (collagène, acides aminés, ADN...) sont faibles et masqués par des signaux parasites. Des chercheurs de notre laboratoire ont donc résolu ces difficultés en améliorant le dispositif de microscopie SRS.

Baptisé SRGold pour "Stimulated raman gain opposite loss detection", ce système breveté en copropriété entre le CNRS et Aix Marseille Université (AMU) a pour effet d’annuler les signaux parasites, tout en multipliant par deux l’intensité du signal des molécules recherchées dans un tissu. Ces résultats sont obtenus grâce à un troisième faisceau laser, qui s’ajoute aux deux lasers qui équipent déjà un dispositif SRS traditionnel.

Le projet de maturation de la SATT Sud-Est, en collaboration avec le CNRS, a pour objectif de montrer l’apport de la technologie SRGold dans un contexte hospitalier. Ce projet est mené en collaboration avec l’Institut Paoli-Calmettes pour la détection de cancers du tube digestif et avec l’Hôpital de la Timone pour la détection de tumeurs cérébrales.

La technologie SRGold devrait permettre d’obtenir des images d’histologie moléculaire d’un tissu cancéreux en quelques minutes, au lieu de 24 heures avec l’histologie standard, et sans avoir recours à aucun marqueur explique Hervé Rigneault, responsable de l’équipe MOSAIC à l’origine de ce projet.

La société HORIBA France est enfin partenaire de ce projet de maturation, qui débouchera sur une licence d’exploitation exclusive concédée par la SATT Sud-Est. A plus long terme, la technologie SRGold étant adaptable à une fibre optique, des applications à l’endoscopie devraient également être envisagées.

Contact : Hervé RIGNEAULT

On the scattering directionality of a dielectric particle dimer of High Refractive Index

"Open access" Article on

Low-losses and directionality effects exhibited by High Refractive Index Dielectric particles make them attractive for applications where radiation direction control is relevant. For instance, isolated metallo-dielectric core-shell particles or aggregates (dimers) of High Refractive Index Dielectric particles have been proposed for building operational switching devices. Also, the possibility of using isolated High Refractive Index Dielectric particles for optimizing solar cells performance has been explored. Here, we present experimental evidence in the microwave range, that a High Refractive Index Dielectric dimer of spherical particles is more efficient for redirecting the incident radiation in the forward direction than the isolated case. In fact, we report two spectral regions in the dipolar spectral range where the incident intensity is mostly scattered in the forward direction. They correspond to the Zero-Backward condition (also observed for isolated particles) and to a new condition, denoted as “near Zero-Backward” condition, which comes from the interaction effects between the particles. The proposed configuration has implications in solar energy harvesting devices and in radiation guiding.

Two particles to scatter the energy in the forward direction when a single particle behaves as a reflector

Revealing the crystalline details of a biomineral shell structure
Towards the understanding of biomineralization thanks to a new x-ray microscopy

Biomineralization processes, which produce outstandingly complex mineralized structures in living organisms, are still poorly understood. Thanks to 3D Bragg ptychography, a recently proposed x-ray microscopy, new structural features of a paradigmatic calcareous biomineral have been revealed, allowing supporting recently proposed biomineralization models [1].

In many living organisms, biomineralization processes regulate the production of the mineralized tissues such as bones, teeth, shells… Deciphering these mechanisms is of crucial importance for materials science, as it will provide bio-inspired strategies for the synthesis of nanostructured inorganic materials using soft chemistry and environmentally friendly processes. Strong impacts are also expected in paleoclimatology that uses biomineral proxies to perform paleoclimate reconstructions. Among the existing biominerals, calcium carbonate biomineral is one of the most striking examples : while it is clear that theories arising from classical crystallization (involving monomer-by-monomer addition) can not explain the production of highly regulated calcareous crystalline biomineral structures as the ones observed in sea urchin or pearl oyster, for instance, the production of this major constituent of the Earth’s crust is still poorly understood.

The present study developed by an interdisciplinary French team lead by Institut Fresnel was motivated by an apparent contradiction observed in biomineral structures : while calcareous crystallizing species present a remarkable architectural diversity at the macro and micro-scales, their sub-micrometric scale is characterized by the consistent observation of a granular, but crystalline, structure. Hence, a proper description of the crystalline features at this mesoscale level, i.e., over a few sub-micrometric (50-500nm) granules, is a key to building realistic scenarios of biomineralization. However, none of the currently used experimental approaches (electron- or x-ray-based diffraction microscopies) is able to provide access to the detailed 3D crystalline granule arrangement.

In 2011, scientists from Institut Fresnel have proposed a new approach, named Bragg ptychography, to image in 3D the crystalline properties of complex materials [2]. This cutting-edge synchrotron-based x-ray microscopy was implemented at a synchrotron source (ESRF-ID13 beamline) and used to reveal the details of the mesocrystalline organization in calcite prisms, the generic mineral units of the pearl oyster shell (Figure). While these prisms are usually described as single-crystal, the 3D image proves the existence of large iso-oriented and iso-strained crystalline domains, slightly different one from the other (Figure). These original results call for specific non-classical crystallization pathways : the highlighted mesocrystalline properties support recent biomineralization models, involving partial fusion of oriented attached nanoparticle assembly and/or liquid droplet precursors.

This study has been performed in the framework of a 4-year ANR grant. It constitutes the starting point of an ERC project, aiming at defining the physical, chemical and biological conditions needed to produce synthetic biominerals, on demand. We expect that the unique properties of the forthcoming synchrotron sources combined to the new (and fast) Bragg ptychography microscopy [3] will enable them to achieve this goal.

Figure : 3D image of the crystalline properties of a biomineral. (A) Optical image of the investigated pearl oyster shell (Pinctada margaritifera) highlighting the investigated region (white rectangle). (B) Zoom-in view of the shell border showing its microscopic structure, composed of juxtaposed calcite prisms. (C) The probed volume (in yellow-grey) represents a small portion of a whole prism. (D) 3D Rotation and (E) strain maps, showing the existence of crystalline domains within the “single-crystalline” like biomineral. Adapted from F. Mastropietro et al., Nature Materials (2017).

References :
[1] F. Mastropietro, P. Godard, M. Burghammer, C. Chevallard, J. Daillant, J. Duboisset, M. Allain, P. Guenoun, J. Nouet, V. Chamard, Revealing crystalline domains in a mollusc shell “single-crystalline” prism, Nature Materials (à paraître).
[2] P. Godard et al., Nature Communications 2, 568 (2011).
[3] S. O. Hruszkewycz, et al., Nature Materials 16, 244 (2017).

Link to other CNRS articles :

Partners :
Institut Fresnel (CNRS Marseille), NIMBE (CEA-CNRS Gif-Sur-Yvette), GEOPS (Université Paris Saclay), Synchrotron Soleil (Gif-Sur-Yvette), ESRF (Grenoble).

Contact :
Virginie Chamard, Equipe Comix (Institut Fresnel)
Tel 04 91 28 28 37 –

Corinne Chevallard, NIMBE (CEA-CNRS)
Tel 01 69 08 52 23 –

A new plasma assisted electron beam deposition machine in Espace Photonique

Within the framework of a project financed by the city of Marseille, the Thin Film Research team of Institut Fresnel has just installed a new Plasma assisted electron beam deposition machine (Bühler SYRUSpro 710) within the Espace Photonique. This AMU technological platform is already equipped with several state-of-the-art machines (e.g. Bühler HELIOS and Bühler SYRUSpro 710) and this new acquisition will help for the development of new and innovative thin film-based components. This machine will be dedicated to the deposition thin films made of infrared materials and to the development of thin layers made of unconventional materials such as phase changing materials (e.g. chalcogenides). In particular, it will enable us to develop broadband antireflection coatings [1.5-15] μm (R&T CNES project), volume structured components (DGA thesis) or optical metasurfaces (Multiwave-funded CIFRE thesis).

Contact RCMO Team : Julien Lumeau
Contact Marseille CityHall : Christophe VOLPE, Office "Immobilier d’Entreprises et Enseignement Supérieur Recherche, Ville de Marseille" -

Researchers of the MOSAIC team at Institut Fresnel have demonstrated the possibility to image, at sub-second time scales, the orientational dynamics of lipids in artificial and cell membranes, without the use of any fluorescence labels.
The gain in imaging rate with respect to other techniques is of a few orders of magnitude ; those methods required indeed minutes to form an orientational image of a few hundreds of micrometers in size.


The optical microscopy method used in the present work records nonlinear coherent Raman scattering signals, in the form of stimulated Raman scattering (SRS) or coherent anti-Stokes Raman scattering (CARS). Those signals originate from the resonant interaction of two pulsed beams with molecular vibrations, here targetting the CH bonds of membrane lipids. Matthias Hofer, Naveen Kumar Balla and Sophie Brasselet have used the lock-in detection method usually implemented for detecting modulated signals in SRS, which exploits modulation transfer from one of the applied incident beam to the other. Here they provided an incident modulation, not anymore in intensity, but rather in polarization. Polarized signals are sensitive to molecular orientations, therefore the obtained modulation is now the signature of molecules being aligned. This scheme has permitted to determine, for each pixel of the image at a rate of 50 microsecond per pixel, both angular distribution width and mean orientation, which are characteristics of molecular organization in the measured lipid membranes at the sub-micrometric scale.

Those signals are rich in information for fundamental and applied biomedical purposes, in particular in tissues such as myelin, a multilayer lipid structure which surrounds and protects our axons. This layered structure is highly perturbed when neurodegenerative diseases develop, such as in Alzheimer’s or multiple sclerosis. This technique could provide early detection of myelin membranes loss of adhesion and detachment, well before they can be visualized at a macroscopic scale. A demonstration of feasability has been recently performed in myelin in the mouse spinal cord, in a work submitted in collaboration with Franck Dbarbieux, INT Marseille.

Reference : M. Hofer, N.K. Balla, S. Brasselet, High speed polarization resolved Coherent Raman Scattering imaging, Optica Vol. 4, Issue 7, pp. 795-801 (2017)

See also : P. Gasecka, A. Jaouen, F.-Z. Bioud, H. Barbosa de Aguiar, J. Duboisset, P. Ferrand, H. Rigneault, N. Balla, F. Debarbieux, S. Brasselet, Degradation of molecular organization of myelin lipids in autoimmune demyelination probed by polarization resolved nonlinear vibrational microscopy, BioRxiV :

Contact : Sophie Brasselet- MOSAIC,

Deux lauréats ERC Consolidator pour l’Institut Fresnel

L’appel ERC Consolidator Grants du Conseil européen de la recherche récompense des chercheurs d’excellence ayant entre sept à douze ans d’expérience après leur thèse. Deux chercheurs de l’Institut Fresnel viennent d’obtenir ce financement s’élevant à environ 2 millions d’euros pour une période de cinq ans.

Virginie Chamard est responsable de l’équipe COMiX. Son projet « 3D-BioMat : Deciphering biomineralization mechanisms through 3D explorations of mesoscale crystalline structure in calcareous biomaterials » propose d’avancer dans la compréhension des processus de biominéralisation grâce au développement d’une nouvelle microscopie aux rayons X, en collaboration avec l’Ifremer (Polynésie Française) et le NIMBE (CNRS/CEA, Saclay).

Site web de l’équipe : COMIX

Jérôme Wenger travaille dans l’équipe MOSAIC. Son projet intitulé « TryptoBoost : Boosting tryptophan fluorescence with optical nanoantennas to watch label-free protein dynamics with single molecule resolution at high concentration » vise à étudier les dynamiques des interactions chimiques de protéines avec de nouveaux outils de microscopie et spectroscopie optiques.

Site web du chercheur :

Crystalline materials : imaging rapidly and efficiently

A new x-ray microscopy, three-dimensional, quantitative and highly-resolved, x-ray microscopy to explore crystalline nanostructures

Understanding shell growth, controlling the optical properties of semiconductors, or even improving the electrical performance of metallic materials are among the many scientific challenges that require knowing the fine properties of crystals at local scales. Due to their long penetration depth, X-rays allows us to probe the inside of a crystal. But producing a quantitative 3D image - providing crystalline strain field information, for instance - with nano-scale resolution remains extremely difficult as a result of the poor efficiency of the available lenses at these wavelengths.
The new approach developed by a Franco-American team and published in Nature Materials greatly simplifies and speeds up the process.

Over the last several years, a so-called lens-less microscopy has emerged : an image of the crystalline properties is retrieved from the diffracted intensities, and numerical methods are used in place of the lenses. To perform such an experiment, the x-ray beam must be coherent, as in the light delivered by a laser. However, the coherence at even the world’s brightest synchrotron x-ray sources is imperfect, such that the size of the sample that can be imaged with lens-less microscopy is typically of the order of a few microns. This hurdle has been cleared in 2011 by the team of V. Chamard at Institut Fresnel (Marseille, France) by demonstrating the possibility to extend arbitrarily the field of view without degrading the resolution.

This microscopy called Bragg ptychography leverages the spatial dependence of the diffraction patterns measured when a nano-focused x-ray beam is scanned along the sample surface. For each position, the 2D
diffraction pattern is recorded. The scanning step, much smaller than the size of the beam spot, produces a strong redundancy in the collected information that enables robust image reconstructions of the sample with new inversion algorithms. Furthermore, three-dimensional information is gained through a tomographic acquisition of the diffracted intensities. Typically, one must measure several hundreds diffraction measurements finely spaced in angle for each beam position on the sample. However, this approach leads to prohibitive total acquisition times (a few tens of hours),

and imposes strong measurement constraints that require specialized experimental set-ups (which only a few beamlines are able to provide), thus preventing the widespread adoption of Bragg ptychography in the scientific community.

The new approach, proposed jointly by researchers from Institut Fresnel (France) and the Argonne National Laboratory (US) greatly simplifies and speeds up this process. Indeed, a huge quantity of information is encoded by the scanning of the beam along the sample, so much so that it becomes possible to perform the measurement at a single viewing angle provided that the intersection between incident diffracted beams is spatially sufficiently well defined. This is indeed the case in Bragg ptychography. The introduction of a modified inversion algorithm gives access to this 3D information in a new and unique way – two dimensions arise from the diffracted signal and one dimension results from the spatial scanning. The new approach, called back-projection Bragg ptychography, marks a conceptual turning point in x-ray microscopy devoted to crystalline materials. The reduction of the total acquisition time, of about a factor 100, and the simplification of the geometry will enable explorations of complex crystalline materials that were not possible to date over a wide range of research areas such as life science and microelectronics.

References :
S. O. Hruszkewycz, M. Allain, M. V. Holt, C. E. Murray, J. R. Holt, P. H. Fuoss and V. Chamard, High-resolution three-dimensional structural microscopy by single-angle Bragg ptychography, Nature Materials 15, December 2016

Contact :
- Virginie Chamard, Institut Fresnel, Equipe Comix

- S. O. Hruszkewycz, Argonne National Laboratory, USA

Other CNRS Links :

- Actualités Scientifiques de l’INSIS, December 20, 2016 -
- "Relations internationales et Europe - ERC", Les Lauréats INSIS 2016 - Consolidator Grants, Virginie Chamard

A new route for looking deeper and brighter in biological tissues

Biological tissues are strongly scattering media, and as such, imaging with high resolution is still remarkably shallow. In particular, multiphoton imaging is strongly based on ballistic light (non-scattered, direction preserved). Because ballistic light intensity decreases exponentially in scattering media, it poses considerable challenges for imaging. Nevertheless, researchers recently found new ways to perform ultradeep imaging, with sub-cellular resolution, by recylcling scattered light itself. Building on these previous work, however exploiting an alternative strategy, we demonstrate record 4000-fold enhancement of nonlinear signal after scattering media, thus enabling highly contrasted nonlinear imaging of biological tissues (collagen fibers).

These remarkable results are possible because of the complex interference pattern arising from multiple scattering phenomena : the speckle. One can “reverse” the complex interference of the speckle into a deterministic shape, e.g. a bright focus. This focus is achieved by using various algorithms which are aided by a feedback mechanism. Traditionally, the feedback for nonlinear imaging is the nonlinear signal itself, which is dim and thus slow. In the new strategy proposed, we exploit the overwhelming linearly scattered light, in opposition to the traditional approach, as a feedback to achieve faster focusing capabilities.

Article :

Reference :
"Enhanced nonlinear imaging through scattering media using transmission-matrix-based wave-front shaping"

Hilton B. de Aguiar1,*, Sylvain Gigan2, and Sophie Brasselet1,†
Phys. Rev. A 94, 043830 – Published 18 October 2016

1Aix-Marseille Université, CNRS, Centrale Marseille, Institut Fresnel UMR 7249, 13013 Marseille, France
2Laboratoire Kastler Brossel, ENS-PSL Research University, CNRS, UPMC Sorbonne Universités, Collège de France, 24 rue Lhomond, 75005 Paris, France

Contact : -


Controlling light scattering and emission with silicon nanoparticles

Light can resonantly interact with subwavelength sized particles, leading to strong enhancements of light scattering and near field intensities in the surrounding of the particles. Metallic nanoparticles have attracted huge efforts over the last 20 years because they host localized surface plasmon resonances, electromagnetic resonances due to the collective oscillation of free electrons. But particles made of insulators can also host electromagnetic resonances, called morphologic or Mie resonances. Theoretical investications carried out at the Institut Fresnel demonstrated that morphologic resonances can yield to the same field enhancements than those yielded by plasmonics particles [1].

A research consortium which includes 2 laboratories of Marseille (Institut Fresnel & CINAM) has recently used the morphologic resonances in dielectric particles made of silicon to enhance to detect individual fluorescent molecules and to imprint colored images without pigments on a surface. Individual fluorescent molecules were observed in a 20 nm nanogap separating 2 silicon particles where the light intensity is strongly enhanced. Dielectric antennas were designed at the Institut Fresnel before being fabricated by the technological platforms hosted by the Institut Fresnel (Photonic space) and by CINAM (Planète) for the coating of the silicon layer and for the lithography and etching of the silicon antennas respectively. The coupling between the 2 silicon particles permits to create a detection volume of the fluorescent signal about one hundred zeptolitres (1 zL=10-21 L) (see the figure on the left). The average number of probed molecules in this volume is decreased by 3600× and becomes smaller than unity while the fluorescent signal is increased by more than 200× [2]. The morphologic resonances in silicon particles have also been used to imprint coloured images without pigment. The resonance frequency depending on the size of the shape of the particle, a palette of structural colours was created simply by moddifying the diameter of the particles. The interest of this technique was highlighted by reproducing a Mondrian’s painting at a 1:1200 scale thanks to silicon particles etched on a glass substrate (see the figure on the right) [3].

These recent advances have been performed without exciting surface plasmon resonances, and by using dielectric materials only. Silicon is ubiquitous in microelectronics and these results in nanophotonics pave the way to bridge the gap between resonant nanophotonics and opto-electronic devices based on silicon technology.

Figure : Gauche : Plateforme de détection moléculaire constituée de 2 particules de Si séparées par un interstice de 20 nm permettant d’exalter et de détecter le signal de fluorescence de molécules individuelles. Droite : Toile de Mondrian reproduite à l’aide de particules de Si. La coloration de ces particules résulte de l’interaction résonante avec la lumière. La couleur est contrôlée par la morphologie des particules
Références :
[1] « Plasmonics » with dielectrics, Optics & Photonics News, February 2016.
[2] Nano Lett. 16, 5143–5151 (2016). Doi : 10.1021/acs.nanolett.6b02076
[3] ACS Nano 10, 7761–7767 (2016). Doi : 10.1021/acsnano.6b03207

Contact Chercheur :
Nicolas BONOD – Institut Fresnel – Tel 04 91 28 28 35

Gold nanoparticles to maintain liquid water at 200°C at ambient pressure
Hydrothermal synthesis at ambient pressure using gold nanoparticles as nanosources of heat
Image de synthèse représentant des microcristaux obtenus par voie hydrothermale sur un tapis de nanoparticules d'or agissant comme nanosources de chaleur sous illumination laser.Artistic view of microcrystals obtained by hydrothermal synthesis using a layer of gold nanoparticles acting as nanosources of heat under laser illumination. In chemical synthesis, hydrothermal reactions involve liquid water between 100°C and 200°C as a solvent. In order to maintain a liquid state at such high temperatures, one has to use a pressure chamber, named an autoclave. This very common approach in chemistry suffers from many limitations, in particular because the reaction medium is closed.

Our researchers have demonstrated the possibility to conduct hydrothermal chemical reactions in an open medium, at ambient pressure, without boiling until 200°C. Such experimental conditions have been obtained at the microscopic scale using gold nanoparticles deposited on a glass substrate and locally heated using an optical microscope and a laser illumination. The absence of boiling up to 230°C and the persistence of a metastable state of water come from the natural absence of nucleation centres in the samples (such as microscopic scratches, dust and roughness).

The chemical reaction consists of the formation of microscopic crystals of indium hydroxide from a solution of indium chloride at 200°C in an aqueous solution, a textbook case in hydrothermal synthesis. Apart from the absence of boiling even at 200°C, other singular observations and interesting benefits have been evidenced, such as kinetics that are 1000 to 10000 times faster than in autoclaves.

This new chemical synthesis technique offers several advantages. As the medium is open, it is possible to add reactants during the reaction. Formation of products can also be observed using optical microscopy means. Finally, this techniques makes it possible as well to spatially structure the growth of solid products on a substrate using a laser beam, opening the path for new applications in micro and nanofabrication.

The concept was imagined by Guillaume Baffou, CNRS research scientist, and the experiments have been conducted by Hadrien Robert, Ph.D. student.
The gold nanoparticle samples have been fabricated by the teams of Julien Polleux (Max Plack Institute, Martinsried, Germany) and Romain Quidant (ICFO, Barcelona, Spain).

Références :
Light-Assisted Solvothermal Chemistry Using Plasmonic Nanoparticles
H. M. L. Robert, F. Kundrat, E. Bermúdez-Ureña, H. Rigneault, S. Monneret, R. Quidant, J. Polleux, and G. Baffou

ACS Omega

ACS Omega 1, 2 (juillet 2016)
DOI : 10.1021/acsomega.6b00019

Contact : Guillaume BAFFOU, CNRS research scientist MOSAIC group, Médaille de bronze 2015 du CNRS

Far-field diffraction microscopy at λ/10 resolution

Researchers of Institut Fresnel in Marseille and LPN Marcoussis

Published in OPTICA Vol 3, N°6, June 2016
Ting Zhang, Charankumar Godavarthi, Patrick Chaumet, Guillaume Maire, Hugues Giovannini, Anne Talneau, Marc Allain, Kamal Belkebir and Anne Sentenac
"Far-field diffraction microscopy at λ/10 resolution"

Tomographic diffraction microscopy is a three-dimensional quantitative optical imaging technique in which the sample is numerically reconstructed from tens of holograms recorded under different angles of incidence. We show that combining the measurement of the amplitude, the phase, and the polarization of the field scattered by the sample with an approximate knowledge of the sample permittivity allows reconstruction of spatially complex samples up to 50 nm resolution. This technique should be particularly useful for imaging objects made of known materials.

Optica - June 2016

Contact : Anne Sentenac, Researcher CNRS, SEMO Group - Phone : +334 91 28 27 90

Identify the good vibrations of molecules

Researchers at the Institut Fresnel in Marseille have developed an imaging technique to determine directly the organization of molecules in the material, and so reveal its structure at the molecular level. The measured signal is not only sensitive to the presence of the molecule but also specific in the way it vibrates, providing structural information previously untapped.

In an article published on 18 May 2016 in the journal Nature Communications, they describe how to shape the polarization of electromagnetic fields to specifically stimulate certain molecular vibrational modes. This method is based on the nonlinear coherent Raman process CARS (coherent anti-Stokes Raman scattering) and group theory concepts. Very simple to implement, this advanced technique is another step in label free microscopy. It offers new perspectives in biology and for biomedical diagnostics, areas where the optical microscope is an essential instrument.

Figure : Imaging of carbon-carbon bonds of myelin in a side section of spinal cord.
The circular structures correspond to the myelin sheaths surrounding the dendrites. The brightness of the image corresponds to the density of carbon-carbon bonds, the color scale corresponds to the organization of the bonds : the isotropic vibration are in red, the uni-directional vibration are in blue.
This image is obtained in a single acquisition without fluorescent probes, and thus allows to provide structural information on the organization of molecules in the sample (image 30 × 30 microns).

Reference : Carsten Cleff, Alicja Gasecka, Patrick ferrand, Hervé Rigneault, Sophie Brasselet et Julien Duboisset
Direct imaging of molecular symmetry by coherent anti-Stokes Raman scattering
Nature Communications 7, Article number 11562 (18 mai 2016)

Contact : Julien Duboisset, Maître de Conférences, Aix-Marseille University, Phone : +334 91 28 80 49

Ultra-wide-range measurements of thin-film filter optical density over the visible and near-infrared spectrum

Reference : M. Lequime, S Liukaityte, M. Zerrad, C. Amra, “Ultra-wide-range measurements of thin-film filter optical density over the visible and near-infrared spectrum,” Opt. Express 23, 26863-26878 (2015).
Selected by Advanced in Enginnering as a Key Scientific Article

See also the paper on NKT Photonics website "EXTREME optical metrology : First broadband measurement of a 12 optical density with 1 nm resolution".

More details on INSIS website (CNRS)

Contact : Michel Lequime and Myriam Zerrad

"Three dimensional nanometer localization of nanoparticles to enhance super-resolution microscopy" Nature Communications du 27 juillet 2015