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Introduction
Publications
Publications (82)
Many processes in microfluidics and biology are driven or affected by viscosity. While several methods are able to measure this parameter globally, very few can provide high resolution viscosity images. Optimizing the locality of viscosity measurements demands smaller probes but also shorter lateral diffusion lengths and measurement times. Here, we...
Single-shot hyperspectral wavefront sensing is essential for applications like spatio-spectral coupling metrology in high power laser or fast material dispersion imaging. Under broadband illumination, traditional wavefront sensors assume an achromatic wavefront, which makes them unsuitable. We introduce a hyperspectral wavefront sensing scheme base...
As miniaturization becomes a growing trend in optical systems, the ability to precisely manipulate wavefronts within micrometric pupils becomes crucial. Extensive efforts to develop integrated micro-optics primarily led to tunable microlenses. Among these approaches, SmartLenses, which use predesigned microheaters to locally change the refractive i...
Quantitative phase imaging enables precise and label-free characterizations of individual nano-objects within a large volume, without a priori knowledge of the sample or imaging system. While emerging common path implementations are simple enough to promise a broad dissemination, their phase sensitivity still falls short of precisely estimating the...
In astronomy or biological imaging, refractive index inhomogeneities of, e.g., atmosphere or tissues, induce optical aberrations that degrade the desired information hidden behind the medium. A standard approach consists of measuring these aberrations with a wavefront sensor (e.g., Shack–Hartmann) located in the pupil plane, and compensating for th...
Aberrations and multiple scattering in biological tissues critically distort light beams into highly complex speckle patterns. In this regard, digital optical phase conjugation (DOPC) is a promising technique enabling in-depth focusing. However, DOPC becomes challenging when using fluorescent guide stars for four main reasons: the low photon budget...
We demonstrate the ability to perform single-shot digital optical phase conjugation from a Stokes shifted fluorescent incoherent guide stars hidden behind a forward scattering sample with a high-resolution wavefront sensor.
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 eithe...
Aberrations and multiple scattering in biological tissues critically distort light beams into highly complex speckle patterns. In this regard, digital optical phase conjugation (DOPC) is a promising technique enabling in-depth focusing. However, DOPC becomes challenging when using fluorescent guide-stars for four main reasons: The low photon budget...
Many processes in microfluidics and biology are driven or affected by viscosity. While several methods are able to measure this parameter globally (AFM, surface acoustic waves, DLS, ...), very few can provide high resolution viscosity images, particularly in living cells. Here, we propose to use sub-micrometer magnetic rods to perform high resoluti...
Individual nanoparticle spectroscopic characterization is fundamental, but challenging in liquids. While confocal selectivity is necessary to isolate a particle in a crowd, Brownian motion constantly offsets the particle from the light collection volume. Here, we present a system able to acquire holograms and reconstruct them to precisely determine...
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 mo...
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 m...
We report on the use of a thin diffuser placed in the close vicinity of a camera sensor as a simple and effective way to superlocalize plasmonic nanoparticles in 3D. This method is based on holographic reconstruction via quantitative phase and intensity measurements of a light field after its interaction with nanoparticles. We experimentally demons...
A novel broadband infrared (IR) speckle imaging system with a thin scatterer and an uncooled microbolometric camera is employed to encode wavefront phase variations as local speckle deformations. The phase reconstruction from speckle shifts using a fast diffeomorphic algorithm ultimately demonstrates IR wavefront reconstruction through complex medi...
Surface modification by photo grafting constitutes an interesting strategy to prepare functional surfaces. Precision applications, however, demand quantitative methods able to monitor and control the amount and distribution of surface modifications, which is hard to achieve, particularly in operando conditions. In this paper, a label‐free, cost‐eff...
Wavefront sensing is a widely used non-interferometric, single-shot, and quantitative technique providing the spatial-phase of a beam. The phase is obtained by integrating the measured wavefront gradient. Complex and random wavefields intrinsically contain a high density of singular phase structures (optical vortices) associated with non-conservati...
Wavefront sensing is a non-interferometric, single-shot, and quantitative technique providing the spatial-phase of a beam. The phase is obtained by integrating the gradient of the wavefront. This integration step is especially delicate in the presence of optical vortices, which are topologically stable singular structures that spontaneously appear...
By measuring the blinking induced by nanorods either in active (magnetically forced) or passive (Brownian) rotation with heterodyne holography, we performed high resolution viscosity imaging, an essential tool to study many microfluidic and biological processes.
Under polarized illumination, non-spherical objects display anisotropic scattering, and their rotation induces a blinking. We present a method based on heterodyne holography to measure images of the Brownian rotation frequencies of gold nanorods over a broad frequency range (0-10 MHz). Since Brownian rotation often occurs on shorter space and time...
Integrating adjustable zoom lenses into mobile phones, miniaturized microscopes or medical endoscopes requires complex optics that can be reshaped electrically within milliseconds. We have recently demonstrated quasi-achromatic, polarization-insensitive electrical components that can apply predetermined, continuous local wavefront shaping with unpr...
Abstract Lighting is rapidly changing with the introduction of light-emitting diodes (LEDs) in our homes, workplaces, and cities. This evolution of our optical landscape raises major concerns regarding phototoxicity to the retina since light exposure is an identified risk factor for the development of age-related macular degeneration (AMD). In this...
Stimulated Raman Scattering (SRS) imaging can be hampered by non-resonant parasitic signals that lead to imaging artifacts and eventually overwhelm the Raman signal of interest. Stimulated Raman gain opposite loss detection (SRGOLD) is a three-beam excitation scheme capable of suppressing this nonlinear background while enhancing the resonant Raman...
Light propagation through scattering samples involves long optical path lengths typically resulting in short spectral correlation widths. Here, we demonstrate experimentally and theoretically a chromato-axial memory effect through volumetric forward-scattering slabs of thickness lying in the range between the scattering mean free path and the trans...
The advent of spatial control over the phase and amplitude of light waves has profoundly transformed photonics, enabling major advances in fields from imaging and information technology to biomedical optics. Here we propose a method of deterministic phase-front shaping using a planar thermo-optical module and designed microheaters to locally shape...
Nanomedicine has emerged as a promising strategy to address some of the limitations of traditional biomedical sensing, imaging and therapy modalities. Its applicability and efficacy are, in part, hindered by the difficulty in both controllably delivering nanoparticles to specific regions and accurately monitoring them in tissue. Gold nanoparticles...
From physics to biology, temperature is often a critical factor. Most existing techniques (e.g. ovens, incubators…) only provide global temperature control and incur strong inertia. Thermoplasmonic heating is drawing increasing interest by giving access to fast, local and contactless optical temperature control. However, tailoring temperature at th...
Using the “memory effect”, we propose and implement a broadband, compact, and cost-effective Wavefront Sensing scheme with a simple thin diffuser. We experimentally demonstrate its capability to provide quantitative phase imaging and nanoparticle superlocalization.
Structured Illumination Microscope allows resolutions of 120 nm or 100 nm when combined with TIRF. Here we present an elegant and simple way of further increasing this resolution to <75nm, adding a nanostructured substrate.
When narrowly distributed silver nanoparticles (NPs) are functionalized by dodecanethiol, they acquire the ability to self-organize in organic solvents into 3D supercrystals (SCs). The NP surface chemistry is shown to introduce a light-driven ther-mo-migration effect, thermophoresis. Using a laser beam to heat the NPs and generate steep thermal gra...
Optical metasurfaces have shown to be a powerful approach to planar optical elements, enabling an unprecedented control over light phase and amplitude. At that stage, where wide variety of static functionalities have been accomplished, most efforts are being directed towards achieving reconfigurable optical elements. Here, we present our approach t...
Coherent Raman scattering processes such as coherent anti-Stokes Raman scattering and stimulated Raman scattering are described in a tutorial way keeping simple physical pictures and simple derivations. The simplicity of the presentation keeps however most of the key features of these coherent and resonant processes and their intimate relation with...
Numerical refocusing in any plane is one powerful feature granted by measuring both the amplitude and the phase of a coherent light beam. Here, we introduce a method based on the first Rytov approximation of scalar electromagnetic fields that (i) allows numerical propagation without requiring phase unwrapping after propagation and (ii) limits the e...
In recent decades, optogenetics has been transforming neuroscience research, enabling neuroscientists to drive and read neural circuits. The recent development in illumination approaches combined with two-photon (2P) excitation, either sequential or parallel, has opened the route for brain circuit manipulation with single-cell resolution and millis...
By partially overcoming the diffraction limit, super-localization techniques have extended the applicability of optical techniques down to the nanometer size-range. Herein, cobalt oxide-based nanoparticles are electrochemically grown onto carbon nanoelectrodes and their individual catalytic properties are evaluated through a combined electrochemica...
We propose and implement a broadband, compact, and low-cost wavefront sensing scheme by simply placing a thin diffuser in the close vicinity of a camera. The local wavefront gradient is determined from the local translation of the speckle pattern. The translation vector map is computed thanks to a fast diffeomorphic image registration algorithm and...
We propose and implement a broadband, compact, and low-cost wavefront sensing scheme by simply placing a thin diffuser in the close vicinity of a camera. The local wavefront gradient is determined from the local translation of the speckle pattern. The translation vector map is computed thanks to a fast diffeomorphic image registration algorithm and...
Single particle electrochemistry at a nanoelectrode is explored by dark-field optical microscopy. The analysis of the scattered light allows in situ dynamic monitoring of the electrodeposition of single cobalt nanoparticles down to a radius of 65 nm. Larger sub-micrometer particles are directly sized optically by edges super-localization and the sc...
Single particle electrochemistry at a nanoelectrode is explored by dark-field optical microscopy. The analysis of the scattered light allows in situ dynamic monitoring of the electrodeposition of single cobalt nanoparticles down to a radius of 65 nm. Larger sub-micrometer particles are directly sized optically by edges super-localization and the sc...
We report a simple add-on for broadband stimulated Raman scattering (SRS) microscopes to enable fast and programmable spectroscopy acquisition. It comprises a conventional dispersive spectrometer layout incorporating a fast digital micromirror device (DMD). The approach is validated by acquiring SRS spectra of standard chemicals. We demonstrate a D...
Statement of significance:
This work highlights how the simple, yet information-rich, animal model C. elegans is ideally suited for preliminary screening of nanoparticles or chemicals mitigating most of the difficulties associated with mammalian animal models, namely the ethical issues, the high cost, and time constraints. This is of particular re...
Interest in nanoparticles has vigorously increased over the last 20 years as more and more studies show how their use can potentially revolutionize science and technology. Their applications span many different academically and industrially relevant fields such as catalysis, materials science, health, etc. Until the past decade, however, nanopartic...
Although extremely sensitive, electrical measurements are essentially unable to discriminate complex chemical events involving individual nanoparticles. The coupling of electrochemistry to dark field imaging and spectroscopy allows triggering the electrodissolution of an ensemble of Ag nanoparticles (by electrochemistry) and inferring both oxidatio...
We present a microscopy technique for the 3D mapping of optical intensity distributions using Brownian gold nanoparticles as local probes, which are superlocalized by dark-field off-axis holography.
We investigate how to extract information on molecular bonds' orientational order in biological samples from polarized coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) microscopy. Experimentally, the mean orientation of the molecular angular distribution, as well as its second and fourth orders of symmetry, are est...
Under illumination at their plasmonic resonance wavelength, metal nanoparticles can turn into efficient nanosources of heat by light absorption. Heating a small volume makes it possible to achieve fast dynamics. In this paper, we investigate theoretically, numerically, and experimentally the temperature distribution of a plasmonic system generated...
We present a rapidly tunable (over 400 cm^− 1) and compact (0.7 m^2 footprint) coherent Raman scattering light source performing both coherent anti-Stokes Raman scattering and stimulated Raman scattering microspectroscopy. We use spectral focusing of a femtosecond Ti:Sapphire pulse and a redshifted soliton generated in a photonic crystal fiber to r...
We introduce a deterministic procedure, named TSUNA for Temperature Shaping Using Nanoparticle Assemblies, aimed at generating arbitrary temperature distributions on the microscale. The strategy consists in (i) using an inversion algorithm to determine the exact heat source density necessary to create a desired temperature distribution and (ii) rep...
We propose a three-color, double-modulation scheme for the background-free detection of stimulated Raman scattering (SRS). We call the scheme stimulated Raman gain and opposite loss detection (SRGOLD). It exploits the symmetric nature of potential parasitic signals (cross phase modulation, two-photon absorption, and thermal effects) to the end of s...
The temperature distribution throughout arrays of illuminated metal nanoparticles is investigated numerically and experimentally. The two cases of continuous and fs-pulsed illumination are addressed. In the case of continuous illumination, two distinct regimes are evidenced: a temperature confinement regime - where the temperature increase remains...
A Quadri-Wave Lateral Shearing Interferometer (QWLSI) is an efficient tool for measuring phase gradients of optical beams along two perpendicular directions. Post-processing integration then allows obtaining the complete phase spatial distribution of the beam. By placing a QWLSI on the exit image plane of such a microscope, we are able to measure t...
We present a method that allows one to measure the real and imaginary parts of the third-order susceptibility in a wide-field coherent anti-Stokes Raman scattering setup using a quadriwave lateral shearing interferometer. This permits the retrieval of the undistorted Raman spectrum and the removal of a nonresonant signal from the surrounding solven...
We report on an optical microscopy technique aimed at measuring the absolute absorption cross section of individual nanoparticles. It relies on the thermally induced variation of the refractive index of the surrounding medium subsequent to light absorption by the nanoparticle. The technique is illustrated on gold nanoparticles featuring a well-defi...
We propose and implement a wide-field microscopy method to retrieve the real and imaginary part of a field emitted by coherent and resonant molecular scatterers. The technique is based on wave-front sensing and does not require the use of any reference beam. We exemplify its ability in wide-field coherent anti-Stokes Raman scattering imaging and re...
We introduce an optical microscopy technique aimed at characterizing the heat generation arising from nanostructures, in a comprehensive and quantitative manner. Namely, the technique permits (i) mapping the temperature distribution around the source of heat, (ii) mapping the heat power density delivered by the source, and (iii) retrieving the abso...
Polarization resolved stimulated Raman scattering (SRS) signal is described in the case of isotropic media and linearly polarized incident fields. The model gives simple expressions for the two perpendicularly polarized SRS signals IX and IY, detected along the X and Y directions, respectively, as a function of the incident pump and Stokes polariza...
We demonstrate stimulated-Raman and coherent anti-Stokes Raman
scattering microscopy with broadband pump and Stokes pulses, using
spectral focussing to attain spectral resolution and to rapidly acquire
spectra within a spectral window determined by the bandwith of the
pulses. As Stokes pulse, we use the redshifted soliton generated in a
photonic-cr...