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Gilles Tessier

Publications and source records attributed to Gilles Tessier.

15 recordsLinked to original sources
arXiv2026

Second-harmonic generation holography with polarization multiplexing for label-free collagen characterization and imaging

Digital holography is an interference-based imaging technique capable of recording both the amplitude and phase of an electromagnetic field. It can be obtained at the laser illumination wavelength, but also with second-harmonic generation, since the latter is produced in a coherent process. Here we describe the development of a harmonic holographic microscope for 3D single-shot mapping of second-harmonic emitters. The knowledge of the scattered field, in amplitude and phase, in a given plane, that of the camera, allows its reconstruction in any other plane using the angular spectrum representation of the optical fields, a process called 3D numerical back-propagation. In order to probe the polarization dependence of the sample nonlinear response, we implement polarization multiplexing, in which a Wollaston prism creates two off-axis reference beams with orthogonal polarizations and non-parallel propagation directions. Each reference only interferes with the corresponding polarization component in the sample SHG emission, thus providing two independent sets of interference fringes which are easily separated in the angular spectrum representation. From a single measurement, two second-harmonic fields corresponding to orthogonal polarizations can be back-propagated. In the particular case of collagen, the second-harmonic polarization state can reveal the orientation or disorder of molecules and fibers. We demonstrate the feasibility of the method by reconstructing the spatial distribution of the second-harmonic field generated by collagen fibers in a rat-tail tendon sample and show that polarization-multiplexed holography can provide single-shot 3D mapping of biophysical parameters such as the helical pitch angle of collagen molecules.

physics.optics↗
arXiv2025

Massart iron oxide nanoparticles in mechanobiology

Magnetic nanoparticles (MNPs) derived from the Massart coprecipitation method have played a pioneering role in bridging materials science and biology. Their magnetic moment and nanoscale dimensions have long enabled applications in magnetic resonance imaging, targeted drug delivery, separation technologies, and hyperthermia. Beyond these well-established uses, a growing research direction has emerged at the interface of physics and biology: the application of MNPs in mechanobiology, the study of how mechanical forces regulate cellular and tissue functions. This review examines how Massart MNPs can be used to generate, transmit, and measure forces within living systems. Particular attention is given to interfacial control through advanced surface chemistries, which ensure colloidal stability, minimize toxicity, and preserve the nanoscale integrity of the particles. We also show that the robustness and scalability of Massart synthesis make it ideally suited to the production of biocompatible nanomaterials in quantities required for comprehensive biological studies. Two complementary approaches are discussed. The first exploits MNP assemblies that arise spontaneously within cells, in the form of endosomes. These compartments enable the application of controlled magnetic forces to study both the formation of reconstructed tissues and organoids, and their viscoelastic response. The second focuses on micrometric magnetic wires fabricated from MNPs, used in active microrheology to probe the cytoplasm of living cells over a wide frequency range. Together, these approaches illustrate how MNP assemblies can accurately quantify cellular and tissue mechanics, providing new opportunities for mechanobiological studies and enabling the development of novel readouts of cellular mechanics with potential diagnostic applications.

cond-mat.soft↗
arXiv2025

Thermally Adaptive Surface Microscopy for brain functional imaging

Fluorescence microscopes can record the dynamics of living cells with high spatio-temporal resolution in a single plane. However, monitoring rapid and dim fluorescence fluctuations, e.g induced by neuronal activity in the brain, remains challenging for 3D-distributed emitters due to out-of-focus fluorescence background, a restricted photon budget, and the speed limit of conventional scanning systems. Here, we introduce a Thermally Adaptive Surface strategy, capable of simultaneously recording, at camera framerate, the activity of 3D-distributed objects. This innovative microscope leverages on an array of thermally tuneable microlenses that offer low chromatic aberration and high transmission, and can be combined with patterned illumination to provide optical sectioning. We demonstrate its potential in vivo, by simultaneously monitoring fast fluorescent dynamics at different depths in the zebrafish larval brain, at a rate of 0.5 kHz and over a large field of view (360um x 360um).

physics.optics↗
arXiv2023

Multiplexed wavefront sensing with a thin diffuser

In astronomy or biological imaging, refractive index inhomogeneities of e.g. atmosphere or tissues induce optical aberrations which degrade the desired information hidden behind the medium. A standard approach consists in measuring these aberrations with a wavefront sensor (e.g Shack-Hartmann) located in the pupil plane, and compensating them either digitally or by adaptive optics with a wavefront shaper. However, in its usual implementation this strategy can only extract aberrations within a single isoplanatic patch, i.e. a region where the aberrations remain correlated. This limitation severely reduces the effective field-of-view in which the correction can be performed. Here, we propose a new wavefront sensing method capable of measuring, in a single shot, various pupil aberrations corresponding to multiple isoplanatic patches. The method, based on a thin diffuser (i.e a random phase mask), exploits the dissimilarity between different speckle regions to multiplex several wavefronts incoming from various incidence angles. We present proof-of-concept experiments carried out in wide-field fluorescence microscopy. A digital deconvolution procedure in each isoplanatic patch yields accurate aberration correction within an extended field-of-view. This approach is of interest for adaptive optics applications as well as diffractive optical tomography.

physics.optics↗
arXiv2022

3D Spectroscopic Tracking of Individual Brownian Nanoparticles during Galvanic Exchange

Monitoring chemical reactions in solutions at the scale of individual entities is challenging: single particle detection requires small confocal volumes which are hardly compatible with Brownian motion, particularly when long integration times are necessary. Here, we propose a real-time (10 Hz) holography-based nm-precision 3D tracking of single moving nanoparticles. Using this localization, the confocal collection volume is dynamically adjusted to follow the moving nanoparticle and allow continuous spectroscopic monitoring. This concept is applied to the study galvanic exchange in freely-moving collo{ï}dal silver nanoparticles with gold ions generated in-situ. While the Brownian trajectory reveals particle size, spectral shifts dynamically reveal composition changes and transformation kinetics at the single object level, pointing at different transformation kinetics for free and tethered particles.

cond-mat.soft↗
arXiv2022

Hollow-core fibers with reduced surface roughness and ultralow loss in the short-wavelength range

While optical fibers display excellent performances in the infrared, visible and ultraviolet ranges remain poorly addressed by them. Obtaining better fibers for the short-wavelength range has been restricted, in all fiber optics, by scattering processes. In hollow-core fibers, the scattering loss arises from the core roughness and represents the limiting factor in reducing their loss regardless of the fiber cladding confinement power. To attain fibers performing at short wavelengths, it is paramount developing means to minimize the height variations on the fiber microstructure boundaries. Here, we report on the reduction of the core surface roughness of hollow-core fibers by modifying their fabrication technique. In the novel process proposed herein, counter directional gas fluxes are applied within the fiber holes during fabrication to attain an increased shear rate on its microstructure. The effect of the process on the surface roughness has been quantified by optical profilometry and the results showed that the root-mean-square surface roughness has been reduced from 0.40 nm to 0.15 nm. The improvement in the fiber core surface quality entailed fibers with ultralow loss in the short-wavelength range. We report on fibers with record loss values as low as 50 dB/km at 290 nm, 9.7 dB/km at 369 nm, 5.0 dB/km at 480 nm, and 1.8 dB/km at 719 nm. The results reveal this new approach as a promising path for the development of hollow-core fibers guiding at short wavelengths with loss that can potentially be orders of magnitude lower than the ones achievable with their silica-core counterparts.

physics.optics↗
arXiv2019

Topological transformations of speckles

Deterministic control of coherent random light is highly important for information transmission through complex media. However, only a few simple speckle transformations can be achieved through diffusers without prior characterization. As recently shown, spiral wavefront modulation of the impinging beam allows permuting intensity maxima and intrinsic $\pm 1$-charged optical vortices. Here, we study this cyclic-group algebra when combining spiral phase transforms of charge $n$, with $D_3$- and $D_4$-point-group symmetry star-like amplitude modulations. This combination allows statistical strengthening of permutations and controlling the period to be 3 and 4, respectively. Phase saddle-points are shown to complete the cycle. These results offer new tools to manipulate critical points in speckles.

physics.optics↗
arXiv2017

Anisotropic super-attenuation of capillary waves on driven glass interfaces

Metrological AFM measurements are performed on the silica glass interfaces of photonic band-gap fibres and hollow capillaries. The freezing of attenuated out-of-equilibrium capillary waves during the drawing process is shown to result in a reduced surface roughness. The roughness attenuation with respect to the expected thermodynamical limit is determined to vary with the drawing stress following a power law. A striking anisotropic character of the height correlation is observed: glass surfaces thus retain a structural record of the direction of the flow to which the liquid was submitted.

cond-mat.soft↗
arXiv2017

Trade-offs between spatial and temporal resolutions in stochastic super-resolution microscopy techniques

Widefield stochastic microscopy techniques such as PALM or STORM rely on the progressive accumulation of a large number of frames, each containing a scarce number of super-resolved point images. We justify that the redundancy in the localization of detected events imposes a specific limit on the temporal resolution. Based on a theoretical model, we derive analytical predictions for the minimal time required to obtain a reliable image at a given spatial resolution, called image completion time. In contrast to standard assumptions, we find that the image completion time scales logarithmically with the ratio of the image size by the spatial resolution volume. We justify that this non-linear relation is the hallmark of a random coverage problem. We propose a method to estimate the risk that the image reconstruction is not complete, which we apply to an experimental data set. Our results provide a theoretical framework to quantify the pattern detection efficiency and to optimize the trade-off between image coverage and acquisition time, with applications to $1$, $2$ or $3$ dimension structural imaging.

physics.bio-ph↗
arXiv2015

High numerical aperture holographic microscopy reconstruction with extended z range

An holographic microscopy reconstruction method compatible with high numerical aperture microscope objective (MO) up to NA=1.4 is proposed. After off axis and reference field curvature corrections, and after selection of the +1 grating order holographic image, a phase mask that transforms the optical elements of the holographic setup into an afocal device is applied in the camera plane. The reconstruction is then made by the angular spectrum method. The field is first propagated in the image half space from the camera to the afocal image of the MO optimal plane (plane for which MO has been designed) by using a quadratic kernel. The field is then propagated from the MO optimal plane to the object with the exact kernel. Calibration of the reconstruction is made by imaging a calibrated object like an USAF resolution target for different positions along $z$. Once the calibration is done, the reconstruction can be made with an object located in any plane $z$. The reconstruction method has been validated experimentally with an USAF target imaged with a NA=1.4 microscope objective. Near-optimal resolution is obtained over an extended range ($\pm 50~μ$m) of $z$ locations.

physics.optics↗
arXiv2015

Holographic microscopy reconstruction in both object and image half spaces with undistorted 3D grid

We propose an holographic microscopy reconstruction method, which propagates the hologram, in the object half space, in the vicinity of the object. The calibration yields reconstructions with an undistorted reconstruction grid i.e. with orthogonal $x$, $y$ and $z$ axis and constant pixels pitch. The method is validated with an USAF target imaged by a $\times$60 microscope objective, whose holograms are recorded and reconstructed for different USAF locations along the longitudinal axis: -75 to +75 $μ$m. Since the reconstruction numerical phase mask, the reference phase curvature and MO form an afocal device, the reconstruction can be interpreted as occurring equivalently in the object or in image half space.

physics.optics↗
arXiv2009

Imaging Gold Nanoparticles in Living Cells Environments using Heterodyne Digital Holographic Microscopy

This paper describes an imaging microscopic technique based on heterodyne digital holography where subwavelength-sized gold colloids can be imaged in cell environment. Surface cellular receptors of 3T3 mouse fibroblasts are labeled with 40 nm gold nanoparticles, and the biological specimen is imaged in a total internal reflection configuration with holographic microscopy. Due to a higher scattering efficiency of the gold nanoparticles versus that of cellular structures, accurate localization of a gold marker is obtained within a 3D mapping of the entire sample's scattered field, with a lateral precision of 5 nm and 100 nm in the x,y and in the z directions respectively, demonstrating the ability of holographic microscopy to locate nanoparticles in living cells environments.

physics.optics↗
arXiv2008

Heterodyne holographic microscopy of gold particles

We report experimental results on heterodyne holographic microscopy of subwavelength-sized gold particles. The apparatus uses continuous green laser illumination of the metal beads in a total internal reflection configuration for dark-field operation. Detection of the scattered light at the illumination wavelength on a charge-coupled device array detector enables 3D localization of brownian particles in water

physics.optics↗
arXiv2007

Temperature measurement of sub-micrometric ICs by scanning thermal microscopy

Surface temperature measurements were performed with a Scanning Thermal Microscope mounted with a thermoresistive wire probe of micrometrSurface temperature measurements were performed with a Scanning Thermal Microscope mounted with a thermoresistive wire probe of micrometric size. A CMOS device was designed with arrays of resistive lines 0.35$μ$m in width. The array periods are 0.8micron and 10micron to study the spatial resolution of the SThM. Integrated Circuits with passivation layers of micrometric and nanometric thicknesses were tested. To enhance signal-to-noise ratio, the resistive lines were heated with an AC current. The passivation layer of nanometric thickness allows us to distinguish the lines when the array period is 10micron. The results raise the difficulties of the SThM measurement due to the design and the topography of ICs on one hand and the size of the thermal probe on the other hand.ic size. A CMOS device was designed with arrays of resistive lines 0.35$μ$m in width. The array periods are 0.8micron and 10micron to study the spatial resolution of the SThM. Integrated Circuits with passivation layers of micrometric and nanometric thicknesses were tested. To enhance signal-to-noise ratio, the resistive lines were heated with an AC current. The passivation layer of nanometric thickness allows us to distinguish the lines when the array period is 10micron. The results raise the difficulties of the SThM measurement due to the design and the topography of ICs on one hand and the size of the thermal probe on the other hand.

physics.class-ph↗