Institut Langevin - Ondes et Images : Biophotonics

Our group is interested in the development of far-field optical techniques for the detection of biomolecules and nanoscale pollutants, as well as for the sub-wavelength imaging of cellular environments. In particular, we develop new approaches to super-resolution microscopy, plasmon-based optical biosensors and interferometric microscopy to detect viruses and image biological tissue. Furthermore, we investigate bioinspired self-assembly strategies for high-scale and low-cost nanofabrication techniques in photonics. For more information :
– Optical Antennas
– Super-Resolution Microscopy
– Full-field Optical Coherence Tomography

Recent publications

From dark modes to topology: light-induced skyrmion generation in a plasmonic nanostructure through the inverse faraday effect Yang, X., Y. Mou, B. Gallas, S. Bidault, and M. Mivelle Nanophotonics 14, no. 14, 2453-2462 (2025) Résumé: Skyrmions are topological structures characterized by a winding vectorial configuration that provides a quantized topological charge. In magnetic materials, skyrmions are localized spin textures that exhibit unique stability and mobility properties, making them highly relevant to the burgeoning field of spintronics. In optics, these structures open new frontiers in manipulating and controlling light at the nanoscale. The convergence of optics and magnetics holds therefore immense potential for manipulating magnetic processes at ultrafast timescales. Here, we explore the possibility of generating skyrmionic topological structures within the magnetic field induced by the inverse Faraday effect in a plasmonic nanostructure. Our investigation reveals that a gold nanoring, featuring a dark mode, can generate counter-propagating photocurrents between its inner and outer segments, thereby enabling the magnetization of gold and supporting a skyrmionic vectorial distribution. We elucidate that these photocurrents arise from the localized control of light polarization, facilitating their counter-propagative motion. The generation of skyrmions through the inverse Faraday effect at the nanoscale presents a pathway towards directly integrating this topology into magnetic layers. This advancement holds promise for ultrafast timescales, offering direct applications in ultrafast data writing and processing.
Nearfield control over magnetic light-matter interactions Reynier, B., E. Charron, O. Markovic, B. Gallas, A. Ferrier, S. Bidault, and M. Mivelle Light: Science and Applications 14, no. 1 (2025) Résumé: Light-matter interactions are frequently perceived as predominantly influenced by the electric field, with the magnetic component of light often overlooked. Nonetheless, the magnetic field plays a pivotal role in various optical processes, including chiral light-matter interactions, photon-avalanching, and forbidden photochemistry, underscoring the significance of manipulating magnetic processes in optical phenomena. Here, we explore the ability to control the magnetic light and matter interactions at the nanoscale. In particular, we demonstrate experimentally, using a plasmonic nanostructure, the transfer of energy from the magnetic nearfield to a nanoparticle, thanks to the subwavelength magnetic confinement allowed by our nano-antenna. This control is made possible by the particular design of our plasmonic nanostructure, which has been optimized to spatially decouple the electric and magnetic components of localized plasmonic fields. Furthermore, by studying the spontaneous emission from the Lanthanide-ions doped nanoparticle, we observe that the measured field distributions are not spatially correlated with the experimentally estimated electric and magnetic local densities of states of this antenna, in contradiction with what would be expected from reciprocity. We demonstrate that this counter-intuitive observation is, in fact, the result of the different optical paths followed by the excitation and emission of the ions, which forbids a direct application of the reciprocity theorem.

100+ patients of corneal Transmission Interferometric Microscopy Mazlin, V., S. Alhaddad, G. Liyanage, Q. Hays, W. Ghouali, C. Baudouin, N. Bouheraoua, and A. C. Boccara Progress in Biomedical Optics and Imaging Proceedings of SPIE 13831, 33 (2026) Résumé: Recently, we introduced a novel method—Transmission Interferometric Microscopy (TIM)—for in vivo imaging of the anterior eye.<sup>1</sup> The technique is inspired by retroillumination approaches that exploit the strong back-scattering of the sclera to create a transmission-illumination geometry for the anterior segment.<sup>2,3</sup> In our implementation, we showed that the spatial coherence of light back-scattered from the sclera can be tuned to boost the interferometric phase contrast of corneal and crystalline-lens cells by several times.<sup>1</sup> To date, TIM has been demonstrated in healthy subjects and in a small number of patients. Here, we report results from the first larger-scale clinical study of this technology, involving over 100 patients with a wide range of corneal pathologies. We demonstrate a direct field-to-field comparison with clinical specular microscopy, showing that this method provides new insights into cellular structure and the inflammatory burden of ocular diseases. Furthermore, we establish the first strategies for obtaining quantitative biomarkers in transmission. Finally, we present the optimized configuration of the transmission device that enabled successful imaging in a clinical research setting.
Metabolic imaging of Fragilariopsis cylindrus in polar night conditions using full-field optical transmission tomography (FFOTT) Joli, N., C. Boccara, B. Bailleul, C. Bowler, and M. Boccara Biomedical Optics Express 17, no. 3, 1540-1549 (2026) Résumé: FFOTT is a non-invasive, non-destructive method of imaging that was found promising for a broad range of applications. We applied FFOTT to compare intracellular dynamic signals, a proxy for cellular metabolic activity. We investigated the metabolic changes associated with the transition from and towards polar night in the polar diatom Fragilariopsis cylindrus, grown under continuous illumination or kept in darkness for six weeks. Our results revealed a tenfold signal decrease in darkness and a rapid signal recovery upon re-illumination. Photosynthetic performance was assessed in parallel. Biovolume determinations allowed the computation of the metabolic rates of F. cylindrus grown under both light and dark conditions, which were compared to the optical signal variations.

A floating body with no preferred orientation: An experimental realization Pontiggia, L., A. Campaniello, and E. Fort American Journal of Physics 94, no. 10, 853-858 (2026) Résumé: Editor's Note: Few students will be surprised to hear that a buoyant sphere can float in any orientation. What might astonish them is the fact that there are other shapes that can float with no preferred orientation! Teachers covering buoyancy will appreciate this striking demonstration and simple tabletop experiment: a heart-shaped object that can settle at any angle.
Time-reversal lens and phase conjugation with an active spatiotemporal interface [Invited] Wildeman, S., A. Eddi, and E. Fort Optical Materials Express 16, no. 10, 3231-3239 (2026) Résumé: Active spatiotemporal interfaces enable wave control through frequency conversion, phase conjugation, and negative refraction. Thin time-modulated interfaces have been predicted to act as flat time-reversal lenses, forming phase-conjugated images on the far side of the interface, yet experiments have mostly addressed phase conjugation or negative refraction in simple beam geometries rather than imaging. Here we realize a flat time-reversal lens for water waves using a subwavelength electrostrictive interface that induces up to a twofold local change in wave velocity. We demonstrate diffraction-limited image formation with a focal spot of half the source wavelength, tunable imaging at complementary frequencies, and control of object-image relations using curved interfaces.

Bottom-up iterative anomalous diffusion detector (BI-ADD) Park, J., N. Sokolovska, C. Cabriel, I. Izeddin, and J. Miné-Hattab Journal of Physics: Photonics 7, no. 4, 045027 (2025) Résumé: In recent years, the segmentation of short molecular trajectories with varying diffusive properties has drawn particular attention of researchers, since it allows studying the dynamics of a particle. In the past decade, machine learning methods have shown highly promising results, also in changepoint detection and segmentation tasks. Here, we introduce a novel iterative method to identify the changepoints in a molecular trajectory, i.e. frames, where the diffusive behavior of a particle changes. A trajectory in our case follows a fractional Brownian motion and we estimate the diffusive properties of the trajectories. The proposed Bottom-up iterative anomalous diffusion detector (BI-ADD) combines unsupervised and supervised learning methods to detect the changepoints. Our approach can be used for the analysis of molecular trajectories at the individual level and also be extended to multiple particle tracking, which is an important challenge in fundamental biology. We validated BI-ADD in various scenarios within the framework of the 2nd anomalous diffusion challenge 2024 dedicated to single particle tracking. Our method is implemented in Python and is publicly available for research purposes.
Quantitative evaluation of methods to analyze motion changes in single-particle experiments Muñoz-Gil, G., H. Bachimanchi, J. Pineda, B. Midtvedt, G. Fernández-Fernández, B. Requena, Y. Ahsini, S. Asghar, J. Bae, F. J. Barrantes, S. W. B. Bender, C. Cabriel, J. A. Conejero, M. Escoto, X. Feng, R. Haidari, N. S. Hatzakis, Z. Huang, I. Izeddin, H. Jeong, Y. Jiang, J. Kæstel-Hansen, J. Miné-Hattab, R. Ni, J. Park, X. Qu, L. A. Saavedra, H. Sha, N. Sokolovska, Y. Zhang, G. Volpe, M. Lewenstein, R. Metzler, D. Krapf, G. Volpe, and C. Manzo Nature Communications 16, no. 1 (2025) Résumé: The analysis of live-cell single-molecule imaging experiments can reveal valuable information about the heterogeneity of transport processes and interactions between cell components. These characteristics are seen as motion changes in the particle trajectories. Despite the existence of multiple approaches to carry out this type of analysis, no objective assessment of these methods has been performed so far. Here, we report the results of a competition to characterize and rank the performance of these methods when analyzing the dynamic behavior of single molecules. To run this competition, we implemented a software library that simulates realistic data corresponding to widespread diffusion and interaction models, both in the form of trajectories and videos obtained in typical experimental conditions. The competition constitutes the first assessment of these methods, providing insights into the current limitations of the field, fostering the development of new approaches, and guiding researchers to identify optimal tools for analyzing their experiments.

Group Members

Permanent Researchers
– Sébastien BIDAULT
– Claude BOCCARA
– Emmanuel FORT
– Ignacio IZEDDIN

Post-doctoral Researchers
– Daria ANDREOLI
– Egidijus AUKSORIUS
– Charles-Edouard LEROUX
– Nemanja MARKESEVIC
– Thu-Mai NGUYEN

PhD Students
– Clement APELIAN
– Vincent BACOT
– Olivier THOUVENIN
– Peng XIAO

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