Offres de thèses

Contexte scientifique

La biominéralisation est la capacité développée par certains organismes vivants à produire des tissus durs souvent cristallisés) pour répondre à leurs besoins fondamentaux, tels que la protection, la capture de la lumière, l’orientation spatiale ou la flottabilité. Il est remarquable que ces cristaux structurés hiérarchiquement se forment dans des conditions physico-chimiques non conventionnelles [1] impliquant un niveau élevé de contrôle biologique par l’intermédiaire de molécules organiques spécifiques produites par l’animal. Ce processus, qui n’est que partiellement compris, ouvrirait des perspectives passionnantes dans de nombreux domaines d’application, tels que la capture du CO2, l’impression 3D, les implants chirurgicaux ou les prothèses dentaires, pour n’en citer que quelques-uns [1]. Parmi les biominéraux, le carbonate de calcium suscite beaucoup d’intérêt en raison de sa présence chez diverses espèces animales telles que les coquillages, les oursins ou les coraux. Un mécanisme général de biominéralisation est proposé, impliquant la production de carbonate de calcium amorphe, qui se cristallise ensuite en calcite ou en aragonite. Les principales questions à traiter sont les suivantes : quelle est la nature structurelle et chimique du ou des précurseurs amorphes ? Quels mécanismes régissent la transition de l’état amorphe à l’état cristallin ? Quel est le rôle et la nature des molécules organiques impliquées dans le cycle de minéralisation ?

À l’Institut Fresnel, nous abordons ces questions en développant de nouvelles techniques optiques appliquées à la question de la biominéralisation. Elles nous permettent respectivement de fournir des informations chimiques structurelles (Raman optique cohérent), à un niveau de résolution et de sensibilité élevé. De plus, nous exploitons la capacité de ces instruments à imager des régions bien définies, représentatives du stade précoce de la biominéralisation, c’est-à-dire là où l’empreinte temporelle de la formation et de la croissance biominérales est clairement visible. Ce projet de thèse de doctorat vise à se concentrer sur le développement de la microscopie Raman cohérente, qui sera ensuite appliquée à des échantillons d’espèces de coraux, idéalement in vivo.Offre de thèse MAROT 09-25

Références
[1] De Yoreo, J. J et al. Science 349 (2015)
[2] J. Duboisset et al., et V. Chamard, Acta Biomaterialia 142 (2022) 194 ; H. Dicko et al., et V. Chamard et J. Duboisset, J. Structural Biology 214 (2022) 107909
[3] K. Koike et al, Biomedical Optics Express 13 (2022) 995

« Optimization of Gap-plasmon Resonators for Environmental Systems »

The proposed PhD project explores nanoparticle-on-mirror (NPoM) architectures for ultra-sensitive environmental detection. By combining plasmonic nanostructures, AI-driven optimization, and advanced nanometrology, we aim to push the boundaries of optical sensing, with a focus on detecting volatile organic compounds.

We are looking for strong candidates with background and interest in optics and numerical programming with skills in experiment and a strong taste in numerical programming.

Only English Speaking candidates : See the whole PhD Offer Here 

Application deadline April 21st, 2025, 05:00 p.m.

DATES LIMITES : 1^ère sélection : 20 mars 2025 – 2^ème tour : 15 avril 2025

offre PhD – « Analyse complexe des réponses spectrales optiques pour déterminer la phase spectrale de composants photoniques » – équipe CLARTE – nicolas.bonod@fresnel.fr

offre PhD « Laser Speckle Contrast Imaging for surgical assistance in thyroid surgery » – équipe DiMABio – julien.fade@fresnel.fr

offre PhD « Characterising the internal structure of asteroids using electromagnetic imaging techniques » – équipe HIPE – christelle.eyraud@fresnel.fr

offre PhD « Optimisation de la précision des thermo-ablations assistées par micro-ondes pour diminuer le taux de récidives cancéreuses et d’ablations incomplètes au niveau hépatique » – équipe HIPE –  pierre.sabouroux@fresnel.fr

offre PhD « Ultrafast nonlinear optical response and dynamics of 2D thin films » – équipe ILM – konstantinos.iliopoulos@fresnel.fr

offre PhD « Detection of nanoplastics with ultraviolet nanophotonics » –  équipe MOSAIC – jerome.wenger@fresnel.fr

offre PhD « Nanoscale imaging of chirality » – équipe MOSAIC – sophie.brasselet@fresnel.fr & miguel.alonso@fresnel.fr

offre PhD « Polarized single molecule imaging of rotational dynamics at the nanoscale » – équipe MOSAIC – sophie.brasselet@fresnel.fr

offre PhD « Spatially structured thin-film optical filters for hyperspectral imaging » – équipe RCMO – julien.lumeau@fresnel.fr & fabien.lemarchand@fresnel.fr

Due to its non-invasive nature and micrometric resolution, optical microscopy is a key tool for observing living samples at the cellular level. However, scattering and distortion caused by the inhomogeneities of biological tissues limit the depth at which an image can be obtained. This major problem has stimulated a great deal of research over the last twenty years, with numerical processing playing an increasingly important role in the image formation.
Our team is specialised in computational imaging. The latter requires an accurate modeling of the link between the recorded data and the sample and sophisticated inversion techniques for recovering an estimation of the sample from the data. In this context, we have shown that multiple scattering, which is usually detrimental to the image formation could be used to improve the spatial resolution of the imager.

Contact :

Anne Sentenac : anne.sentenac@fresnel.fr

Patrick Chaumet : patrick.chaumet@fresnel.fr

Guillaume Maire : guillaume.maire@fresnel.fr

Kamal Belkebir : kamal.belkebir@fresnel.fr

SEMO_PhD

Description du sujet : Dans le cadre de cette thèse, nous chercherons à développer de nouvelles procédures d’imagerie adaptées à ce cas d’étude (à partir de celles existantes), de manière à extraire des informations quantitatives sur la structure interne des comètes et astéroïdes et ceci, à partir des données pouvant être mesurées dans la réalité des expériences spatiales. Ces procédures seront appliquées au cas du radar JuRa qui va sonder l’astéroïde Didymos afin de préparer l’exploitaton des donnéees du radar.
Pour cela, des études seront conduites sur le choix des paramètres d’entrée, sur les informations les plus pertinentes pouvant être introduites dans ces procédures d’imagerie (notamment fournies par d’autres capteurs), et sur le choix des grandeurs à reconstruire. Les procédures seront confrontées à des expérimentations réalisées en laboratoire, en chambre anéchoïque sur des analogues d’astéroïdes.
L’étudiant.e bénéficiera des collaborations nationales et internationales en cours avec des chercheurs en planétologie et en mathématiques appliquées.

Sujet_these_Eyraud

PhD Offer « Ultrafast nonlinear optical response and dynamics of 2D thin films » in ILM group

Application Deadline : 31/03/2025 on AMU EURAXESS PORTAL or by Email konstantinos.iliopoulos@fresnel.fr

DESCRIPTION :  Two-dimensional thin films are well-known for their high optical nonlinearities. For this reason, they are currently the best candidates for mode-locking of laser systems.¹ Recently, during two PhD thesis, we optimized Sb₂Te₃ and Bi₂Se₃ layers to obtain significant nonlinear absorption. More specifically, the saturable absorption behavior obtained was the highest ever reported in the field of nonlinear optics by similar experimental techniques.^2-5  These high optical nonlinearities are emanating from the topological insulator character of the layers which can be observed in 2D structures. However, the relation between the structural characteristics of topological insulators and their optical nonlinearities is still not sufficiently explored. The target of the thesis is to shed light on the origins of the nonlinear optical properties of 2D topological insulators (like Sb₂Te₃, Bi₂Te₃ and Bi₂Se₃). This will allow a better understanding of the physical mechanisms that give rise to the nonlinear refraction and absorption of the thin films. The objectives of the thesis are the following:

Objective 1 : Thin film deposition and preparation. The thin films will be deposited by the electron beam deposition technique available in a modern facility established in Fresnel Institute (Espace Photonique). An optimal crystallization of the thin film layers is necessary in order to enhance the optical nonlinearities. This is currently done by our group by heating the thin films in an oven. During this thesis a new experimental setup will be built, which will allow a higher precision annealing by using a high repetition rate femtosecond laser.

Objective 2 : Nonlinear optical studies. The deposited and optimized 2D layers will be studied by means of the Z-scan technique, already existing in Institute Fresnel. For these studies a femtosecond laser system will be employed. This is a hybrid (crystal/fiber), passively mode-locked laser delivering 400 fs duration pulses at 1030 nm. The oscillator provides pulses at a 40 MHz repetition rate. An optical parametric amplifier has been very recently installed at the exit of the femtosecond laser, which will allow tuning the laser wavelength at the UV, visible and IR parts of the spectrum (200 nm to 2.5 μm). This is an ideal laser system for the thesis, as it will allow the investigation of the impact of the repetition rate (tunable between 1 Hz and 40 MHz), the wavelength and the pulse duration (the latter can be adjusted from 80 fs up to 20 ps) on the nonlinear optical responses.

Objective 3 : Ultrafast dynamics of the 2D layers. A deeper understanding of the laser-matter interaction will be achieved through a thorough study of the carrier dynamics of the topological insulators during their excitation with light. For this reason, a pump-probe optical spectroscopy setup will be built by the PhD student. Briefly, the higher energy pump pulses will allow to generate photo-excited carriers, while less intense probe pulses will detect the transmittance change of the sample. These studies will allow a precise study for several different delays between the pump and the probe pulses.

The combination of these two approaches will allow retrieving the full spectral dependence of the investigated topological insulators and understand the underlying photon/ electron interactions.
Apart from the nonlinear optical investigations the student will participate at all the experimental steps required for obtaining giant optical nonlinearities. This procedure includes thin film deposition, annealing, X-Ray Diffraction studies (XRD), Scanning Electron Microscopy (SEM) studies and Atomic Force Microscopy (AFM) investigations.

Main sub research field : Optics, Nonlinear optics, Thin Films

Starting Date : 01/09/2025

Duration : 36 months

Salary : Approximately 1 700€ net

Requested documents : CV, Grades (Master 1 & 2), Motivation Letter

Contact : Dr Konstantinos ILIOPOULOS – ILM group

Application Deadline : 31/03/2025 on AMU EURAXESS PORTAL or by Email konstantinos.iliopoulos@fresnel.fr

Bibliography :
1) M. Kowalczyk et al. Optical Materials Express 6, 2273-2282 (2016)
2) R.-N. Verrone et al. ACS Applied Nano Materials 3, 7963-7972 (2020)
3) C. Moisset et al. Nanoscale Adv. 2, 1427-1430 (2020)
4) A. Karimbana-Kandy et al. Optical Materials 143, 114211 (2023)

Notre Mission : Our rent advances in coherent Raman microscopy allow for the real-time generation of artificially stained images of cancer samples which previously required time-consuming histopathological staining procedures. These images serve as feedback for surgeons to guide cancer surgery. As the main challenge, the examination of thick cancer samples is currently impossible, as all excitation light in coherent Raman microscopy is scattered forward and must pass through the sample. Within this project, you will develop a new coherent Raman technique called coherent Stokes Raman scattering (CSRS) microscopy. As the game-changer, CSRS will send the signal photons directly into the backward direction and, therefore, enable the investigation of thick, non-transparent cancer samples. Moreover, we will use CSRS’ backscattering property to record the CSRS spectrum of tissue at unprecedented speed levels using novel spectrometer concepts and multi-focus or wide-field illumination approaches. From these CSRS spectra, a precise diagnosis of the cancerous tissue will be derived by machine learning algorithm. Your mission is to set up and characterize these novel microscopy techniques and evaluate their functionality on cancer tissue.

Construction – You will build from scratch one or more new coherent Stokes Raman microscopes.
Simulation – You simulate your experiments in Matlab or Python. We work in close cooperation with theoretical physicists.
(Optional) experiments – You will examine cancer samples with your microscope and predict the malignancy of the tissue with the help of our machine learning experts at the institute.

Profil Recherché :
Attitude : For you, research is a vocation and not just a source of income. High levels of initiative, creativity and curiosity are expected from you.
Willingness to perform : Within your university education you were among the top 25%.

Qualification : You have completed a degree in the field of photonics, e.g. physics, physical chemistry or similar. Asset but is not required: You have developed microscopy techniques or other imaging methods during your master’s thesis.

Language : The communication between scientists happens in English. Knowledge of French for everyday use can be acquired when you have started your position.

Détails de l’Offre de Thèse :
Ressources : Your project is funded by an ERC consolidators’ grant (sCiSsoRS, 2.4 M€). You will work with state-of-the-art equipment and your results are of high general interest. You will have a postdoc at your side for general support.

Tâches : You can focus 100% on research. No distractions.

Esprit d’Equipe : You will be part of a high-performing, multinational group of 10 independent scientists working in a team with 30 postdocs and PhD students to advance cutting-edge research in biomedical imaging.

Encadrement : You will be in close contact with your supervisor. Upcoming challenges are addressed on the same day.

Rémunération : You will benefit from a competitive European salary level starting from ≥ 1700€.

Cette offre vous intéresse ? Envoyez votre lettre de motivation, votre CV détaillé, une lettre de recommandation et une référence à sandro.heuke@fresnel.fr

2024 PhD position MOSAIC Group

Context : This PhD thesis topic will focus on the theoretical, numerical, and experimental development of metasurfaces for the optical detection of chiral molecules. To achieve this, we aim to max-imize the chirality of the electromagnetic field at nanoscale volumes close to the metasur-face. Optical detection of enantiomers is motivated by numerous applications, but studies have mostly focused on the development of chiral nanostructures inducing strong circular dichroism. In this thesis topic, we aim to create intense chiral fields with achiral structures.

Theoretical and Numerical Work : From a theoretical standpoint, we will study the conditions that maximize the chirality of nearfields by studying the spectral response in the complex frequency plane. The conditions capable of maximizing both electric and magnetic near fields are not yet fully understood, and we will seek to establish the solid theoretical foundations leading to these conditions in metasurfaces, particularly through the complex analysis of metasurface reflection and transmission coefficients, as well as through algorithmic optimization approaches. A second major aspect of this thesis work will involve modeling a chiral medium. This work requires working with complete constitutive relations and their implementation into numerical models for solving Maxwell’s equations. Subsequently, a layer of chiral material will be integrated into the immediate vicinity of the metasurface to evaluate the influence of the metasurface on circular dichroism. Once all these theoretical and numerical elements are
achieved and mastered, we can develop and use optimization algorithms to determine the optimal parameters of the metasurface.

Experimental Developments : We will collaborate with the Planète technological platform hosted by CINAM to fabricate samples. The PhD student will follow a 15-day training in the cleanroom (training certified by the doctoral school), and thereafter, the PhD student can continue technological developments to fabricate the samples. The metasurface will be optically characterized at the Fresnel Institute and/or at the INSP and LRS, two laboratories located on the Jussieu campus in Paris Centre involved in the joint project. These works will be carried out within the framework of a project funded by the National Research Agency entitled NanoSpeCD.

Directeur de thèse : Nicolas Bonod, Guillaume Demesy, Brian Stout