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.

Transmission interference microscopy of anterior human eye Alhaddad S., , Ghouali W., Baudouin C., A. C. Boccara, and V. Mazlin Nature Communications 16, no. 1 (2025) Résumé: Cellular imaging of the human anterior eye is critical for understanding complex ophthalmic diseases, yet current techniques are constrained by a limited field of view or insufficient contrast. Here, we demonstrate that Ernst Abbe’s foundational principles on the interference nature of transmission microscopy can be applied in vivo to the human eye to overcome these limitations. The transmission geometry in the eye is achieved by projecting illumination onto the posterior eye (sclera) and using the back-reflected light as a secondary illumination source for anterior eye structures. Specifically, we show that the tightly localized illumination spot at the sclera functions analogously to a closed condenser aperture in conventional microscopy, significantly enhancing interference contrast. This enables clear visualization of cells and nerves across all corneal layers within an extended 2 mm field of view. Notably, the crystalline lens epithelial cells, fibers, and sutures are also distinctly resolved. In patients, Fuch’s endothelial dystrophy - a major ophthalmic disease affecting 300 million people - is highlighted under a transmission contrast, providing complementary information to traditional reflection contrast. Constructed using consumer-grade cameras, the instrument offers a path toward broad adoption for pre-screening and surgical follow-up, as well as for diagnosing corneal infections in low-resource settings, where anterior eye diseases are most prevalent.
Label-free metabolic imaging and energy costs in Chlamydomonas Boccara, M., K. Wostrikoff, B. Bailleuil, and C. Boccara The European Physical Journal E 48, no. 6-7 (2025) Résumé: We developed a label-free optical microscopy method to study movements of different frequencies and amplitudes within a cell. We use optical transmission tomography (OTT) that operates in transmission, and we record the changes of signal values of all the pixels of movies taken for a few seconds (dynamic signal). This signal is a metabolic signal in algae as it decreased in the presence of photosystem II inhibitors or when samples were illuminated at wavelengths where the photoreceptors are poorly operative. We used as model organism Chlamydomonas for which mutants are available. We used a mutant deleted of the chloroplastic gene encoding the large subunit of the Rubisco, ΔrbcL. This mutant is unable to fix atmospheric CO<inf>2</inf> and is devoid of pyrenoid. We compared the dynamic signal between wild-type strain and ΔrbcL mutant of Chlamydomonas grown in dark condition and found it to be 5 to 10 times higher. This mutant overproduced starch, and we tempted to associate the metabolic signal to the cost in ATP<inf>eq</inf> consumption for building starch. The method is easy to implement and could be very valuable for studies of phytoplankton in situ or virus-infected cells.

Optophysiology using dynamic full-field optical coherence tomography (D-FF-OCT) Norberg, N., S. Azzollini, T. Monfort, J. Granier, O. Thouvenin, and K. Grieve Progress in Biomedical Optics and Imaging - Proceedings of SPIE 13305, 16 (2025) Résumé: We present an approach for assessing photoreceptor function using dynamic full-field optical coherence tomography (DFF-OCT) in an ex-vivo macaque retinal explant. Our non-invasive method reveals photoreceptor function through high-resolution (0.4 µm transverse, 0.7 µm axial) D-FF-OCT imaging, coupled with a signal processing pipeline that quantifies changes in photoreceptor intensity variability relative to pre-photostimulation levels. Following dark adaptation, photoreceptor responses to a single green light flash (530 nm, 100 ms) were recorded and analyzed. Regions of interest (ROIs) were segmented using Cellpose and classified as responders or non-responders based on intensity thresholds relative to pre-stimulation variability. Of the photoreceptor cells analyzed (n=1075), 62% were identified as responders, showing a significant increase in intensity variability compared to controls. The optophysiology curve revealed a rapid divergence in stimulated and control conditions post-flash, underscoring the ability of D-FF-OCT to capture light-induced functional changes. This study demonstrates that optophysiology using D-FF-OCT offers a robust, non-invasive alternative for photoreceptor functional assessment.
Rolling-phase dynamic full-field OCT Monfort, T., K. Grieve, and O. Thouvenin Optics Letters 50, no. 7, 2239-2242 (2025) Résumé: Dynamic full-field optical coherence tomography (DFFOCT) has recently emerged as an invaluable label-free microscopy technique, owing to its sensitivity to cell activity, as well as speed and sectioning ability. However, the quality of DFFOCT images is often degraded due to phase noise and fringe artifacts. In this work, we present a new implementation, to the best of our knowledge, named rolling-phase (RP) DFFOCT, in which the reference arm is slowly scanned over magnitudes exceeding 2π. We demonstrate mathematically and experimentally that it shows superior image quality while enabling to extract both static and dynamic contrast simultaneously. We showcase RP-DFFOCT on a macaque retinal explant and demonstrate its ability to better resolve subcellular structures, including intranuclear activity.

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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