Single-shot digital optical fluorescence phase conjugation through forward multiple-scattering samples.

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 available, the large spectral bandwidth of the fluorescent signal, the Stokes shift between the emission and the excitation wavelength, and the absence of reference beam preventing holographic measurement.

3D nanoparticle superlocalization with a thin diffuser.

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 demonstrate that this thin diffuser can be used as a simple add-on to a standard bright-field microscope to allow the localization of 100 nm gold nanoparticles at video rate with nanometer precision (1.

Three-dimensional broadband light beam manipulation in forward scattering samples.

Focusing light into highly disordered biological tissue is a major challenge in optical microscopy and biomedical imaging due to scattering. However, correlations in the scattering matrix, known as "memory effects", can be used to improve imaging capabilities. Here we discuss theoretically and numerically the possibility to achieve three-dimensional ultrashort laser focusing and scanning inside forward scattering media, beyond the scattering mean free path, by simultaneously taking advantage of the angular and the chromato-axial memory effects.

Focusing large spectral bandwidths through scattering media.

Wavefront shaping is a powerful method to refocus light through a scattering medium. Its application to large spectral bandwidths or multiple wavelengths refocusing for nonlinear bio-imaging in-depth is however limited by spectral decorrelations. In this work, we demonstrate ways to access a large spectral memory of a refocus in thin scattering media and thick forward-scattering biological tissues.

ATP6AP2 variant impairs CNS development and neuronal survival to cause fulminant neurodegeneration.

Vacuolar H+-ATPase-dependent (V-ATPase-dependent) functions are critical for neural proteostasis and are involved in neurodegeneration and brain tumorigenesis. We identified a patient with fulminant neurodegeneration of the developing brain carrying a de novo splice site variant in ATP6AP2 encoding an accessory protein of the V-ATPase. Functional studies of induced pluripotent stem cell-derived (iPSC-derived) neurons from this patient revealed reduced spontaneous activity and severe deficiency in lysosomal acidification and protein degradation leading to neuronal cell death.

Wrapping-free numerical refocusing of scalar electromagnetic fields.

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 effect of artificial phase singularities that appear upon numerical defocusing when the measurement noise is mixing with the signal. We demonstrate the feasibility of this method with both scalar electromagnetic field simulations and real acquisitions of microscopic biological samples imaged at high numerical aperture.

Wavefront sensing with a thin diffuser.

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 integrated to reconstruct the wavefront profile.

Otoferlin acts as a Ca sensor for vesicle fusion and vesicle pool replenishment at auditory hair cell ribbon synapses.

Hearing relies on rapid, temporally precise, and sustained neurotransmitter release at the ribbon synapses of sensory cells, the inner hair cells (IHCs). This process requires otoferlin, a six C-domain, Ca-binding transmembrane protein of synaptic vesicles. To decipher the role of otoferlin in the synaptic vesicle cycle, we produced knock-in mice () with lower Ca-binding affinity of the CC domain.

Vortex-free phase profiles for uniform patterning with computer-generated holography.

Computer-generated holography enables efficient light pattern generation through phase-only wavefront modulation. While perfect patterning usually requires control over both phase and amplitude, iterative Fourier transform algorithms (IFTA) can achieve phase-only approximations which maximize light efficiency at the cost of uniformity. The phase being unconstrained in the output plane, it can vary abruptly in some regions leading to destructive interferences.

Complementary Speckle Patterns: Deterministic Interchange of Intrinsic Vortices and Maxima through Scattering Media.

Intensity maxima and zeros of speckle patterns obtained behind a diffuser are experimentally interchanged by applying a spiral phase delay of charge ±1 to the impinging coherent beam. This transform arises from the expectation that tightly focused beams, which have a planar wave front around the focus, are so changed into vortex beams and vice versa. The statistics of extrema locations and the intensity distribution of the so-generated "complementary" patterns are characterized by numerical simulations.

Computer Generated Holography with Intensity-Graded Patterns.

Computer Generated Holography achieves patterned illumination at the sample plane through phase modulation of the laser beam at the objective back aperture. This is obtained by using liquid crystal-based spatial light modulators (LC-SLMs), which modulate the spatial phase of the incident laser beam. A variety of algorithms is employed to calculate the phase modulation masks addressed to the LC-SLM.

Superresolving dendritic spine morphology with STED microscopy under holographic photostimulation.

Emerging all-optical methods provide unique possibilities for noninvasive studies of physiological processes at the cellular and subcellular scale. On the one hand, superresolution microscopy enables observation of living samples with nanometer resolution. On the other hand, light can be used to stimulate cells due to the advent of optogenetics and photolyzable neurotransmitters.

Superresolution Imaging of Optical Vortices in a Speckle Pattern.

We characterize, experimentally, the intensity minima of a polarized high numerical aperture optical speckle pattern and the topological charges of the associated optical vortices. The negative of a speckle pattern is imprinted in a uniform fluorescent sample by photobleaching. The remaining fluorescence is imaged with superresolution stimulated emission depletion microscopy, which reveals subdiffraction fluorescence confinement at the center of optical vortices.

Astrocyte VAMP3 vesicles undergo Ca2+ -independent cycling and modulate glutamate transporter trafficking.

Key Points: Mouse cortical astrocytes express VAMP3 but not VAMP2. VAMP3 vesicles undergo Ca(2+) -independent exo- and endocytotic cycling at the plasma membrane. VAMP3 vesicle traffic regulates the recycling of plasma membrane glutamate transporters.

Zero-order suppression for two-photon holographic excitation.

Wavefront shaping with liquid-crystal spatial light modulators (LC-SLMs) is frequently hindered by a remaining fraction of undiffracted light, the so-called "zero-order." This contribution is all the more detrimental in configurations for which the LC-SLM is Fourier conjugated to a sample by a lens, because in these cases this undiffracted light produces a diffraction-limited spot at the image focal plane. In this Letter we propose to minimize two-photon (2P) excitation of the sample, resulting from this unmodulated light, by introducing optical aberrations to the excitation beam.

Cdc42 controls the dilation of the exocytotic fusion pore by regulating membrane tension.

Membrane fusion underlies multiple processes, including exocytosis of hormones and neurotransmitters. Membrane fusion starts with the formation of a narrow fusion pore. Radial expansion of this pore completes the process and allows fast release of secretory compounds, but this step remains poorly understood.

Quantitative confocal spiral phase contrast.

We demonstrate quantitative phase delay measurements with a spiral phase contrast microscope working in confocal mode. Such a confocal configuration is sensitive to weak phase objects due to background rejection but does not give direct access to the phase delay introduced by the sample. We develop a theory showing that shifting the illumination spot relative to the detector gives access to the local phase gradient in the first-order approximation.

STED microscope with spiral phase contrast.

Stimulated Emission Depletion (STED) microscopy enables superresolution imaging of fluorescently marked nano-structures in vivo. Biological investigations are often hindered by the difficulty of relating super-resolved structures to other non-labeled features. Here we demonstrate that the similarity in optical design of Spiral Phase Contrast (SPC) and STED microscopes allows straightforward implementation of a phase contrast channel into a STED microscope in widefield and scanning modes.

LCoS nematic SLM characterization and modeling for diffraction efficiency optimization, zero and ghost orders suppression.

Pixilated spatial light modulators are efficient devices to shape the wavefront of a laser beam or to perform Fourier optical filtering. When conjugated with the back focal plane of a microscope objective, they allow an efficient redistribution of laser light energy. These intensity patterns are usually polluted by undesired spots so-called ghosts and zero-orders whose intensities depend on displayed patterns.

Three-dimensional holographic photostimulation of the dendritic arbor.

Digital holography is an emerging technology that can generate complex light patterns for controlling the excitability of neurons and neural circuits. The strengths of this technique include a high efficiency with which available light can be effectively utilized and the ability to deliver highly focused light to multiple locations simultaneously. Here we demonstrate another strength of digital holography: the ability to generate instantaneous three-dimensional light patterns.

The influence of resonant absorption and heating on the equilibrium size of aqueous-solute aerosol droplets.

The time-dependent evolution in the equilibrium size of an optically trapped aqueous sodium chloride droplet (>2 microm radius) within an environment of varying relative humidity (RH) is shown to depend on both the depression in vapour pressure due to the presence of the solute and the elevation in temperature due to optical absorption. In particular, the level of optical absorption is highly dependent on the size of the droplet relative to the wavelength of the absorbed light. Thus, as the droplet size tunes into a Mie resonance at the trapping laser wavelength, the increased level of optical absorption leads to an elevation in droplet temperature.

Longitudinal optical binding of high optical contrast microdroplets in air.

Binding along the beam axis (which we shall call "longitudinal optical binding") has been observed between micron-sized oil droplets in a three dimensional optical trap in air. We argue that it is the high optical contrast which is responsible for the exceptionally stable doublet structures observed experimentally. It was also observed that optically bound doublets tend to cling to interference fringes created by the two counterpropagating beams.