Swept-wavelength null polarimetry for highly sensitive birefringence laser scanning microscopy.

We have recently demonstrated a high-speed null polarimeter [Opt. Express30, 18889 (2022)10.1364/OE.

Systematic errors in a swept-wavelength null polarimeter for weak linear retardance measurements.

We recently developed a high speed null polarimeter [Opt. Express30, 18889 (2022)OPEXFF1094-408710.1364/OE.

Swept-wavelength null polarimeter for high-speed weak anisotropy measurements.

Null-polarimeters provide the best sensitivity to anisotropy measurements and so far have been developed for the detection of small optical activities. This paper revisits null polarimetry through an original configuration based on the concept of spectrally encoded light polarization, in order to measure, with unprecedented speed, either linear or circular retardance with the same degree of sensitivity . Using passive polarization optics and a high speed wavelength swept laser source, the achieved single-pass sensitivity was 55nrad/Hz and 45nrad/Hz for respectively linear and circular retardance considering a minimum acquisition time of 10 µs.

Gastric cancer multicellular spheroid analysis by two-photon microscopy.

Gastric cancer (GC) is highly deadly. Three-dimensional (3D) cancer cell cultures, known as spheroids, better mimic tumor microenvironment (TME) than standard 2D cultures. Cancer-associated fibroblasts (CAF), a major cellular component of TME, promote or restrain cancer cell proliferation, invasion and resistance to drugs.

Linear diattenuation imaging of biological tissues with near infrared Mueller scanning microscopy.

Among the multitude of optical polarization contrasts that can be observed in complex biological specimens, linear diattenuation (LD) imaging has received little attention. It is indeed challenging to image LD with basic polarizing microscopes because it is often relatively small in comparison with linear retardance (LR). In addition, interpretation of LD images is not straightforward when experiments are conducted in the visible range because LD can be produced by both dichroism and anisotropic scattering.

Optimization of fast spectrally encoded Mueller polarimeters for real-time monitoring.

In this paper, we report a generalized theoretical framework on spectrally encoded polarimeters to display in real time both linear and circular retardance as well as linear and circular diattenuation on the basis of a recent experimental work detailed in Sci. Rep.9, 3972 (2019)SRCEC32045-232210.

Polarization-resolved second harmonic microscopy of skeletal muscle in sepsis.

Polarization-resolved second harmonic generation (P-SHG) microscopy is able to probe the sub-micrometer structural organization of myosin filaments within skeletal muscle. In this study, P-SHG microscopy was used to analyze the structural consequences of sepsis, which is the main cause of the critical illness polyneuromyopathy (CIPNM). Experiments conducted on two populations of rats demonstrated a significant difference of the anisotropy parameter between healthy and septic groups, indicating that P-SHG microscopy is promising for the diagnosis of CIPNM.

Fast spectrally encoded Mueller optical scanning microscopy.

Mueller microscopes enable imaging of the optical anisotropic properties of biological or non-biological samples, in phase and amplitude, at sub-micrometre scale. However, the development of Mueller microscopes poses an instrumental challenge: the production of polarimetric parameters must be sufficiently quick to ensure fast imaging, so that the evolution of these parameters can be visualised in real-time, allowing the operator to adjust the microscope while constantly monitoring them. In this report, a full Mueller scanning microscope based on spectral encoding of polarization is presented.

Snapshot second-harmonic generation polarimeter based on spectral analysis.

A new high-speed second-harmonic generation (SHG) polarimetric method is reported. It is based on the spectral analysis of the SHG radiation emitted by a nonlinear medium excited with circularly polarized femtosecond laser pulses. The setup uses only passive components for polarization encoding and a fast spectrometer for spectral analysis.

Scanning Mueller polarimetric microscopy.

A full Mueller polarimeter was implemented on a commercial laser-scanning microscope. The new polarimetric microscope is based on high-speed polarization modulation by spectral coding using a wavelength-swept laser as a source. Calibration as well as estimation of the measurement errors of the device are reported.

A non-hypocholesterolemic atorvastatin treatment improves vessel elasticity by acting on elastin composition in WHHL rabbits.

Background And Aims: Statins are prescribed for their preventative effects within atherosclerosis development. To our knowledge, no study focusing on very low-dose (non-hypolipidemic effect) and long-term atorvastatin treatment in vivo was available. Our aim was to assess the effect of such atorvastatin treatment on the mechanical and functional characteristics of arteries in the context of primary prevention.

Evaluation of area-based collagen scoring by nonlinear microscopy in chronic hepatitis C-induced liver fibrosis.

In this paper we analyze a fibrosis scoring method based on measurement of the fibrillar collagen area from second harmonic generation (SHG) microscopy images of unstained histological slices from human liver biopsies. The study is conducted on a cohort of one hundred chronic hepatitis C patients with intermediate to strong Metavir and Ishak stages of liver fibrosis. We highlight a key parameter of our scoring method to discriminate between high and low fibrosis stages.

100 kHz Mueller polarimeter in reflection configuration.

A new setup is proposed to perform high-speed Mueller polarimetry by spectral coding of polarization in a reflection configuration. The system uses a swept laser source and a photodiode, which results in a simple optical setup that allows measurement of Mueller matrices at 100 kHz repetition rate. A special focus is made on the influence of the cube beam splitter polarimetric response, which is essential to measurements in a reflection configuration.

Measuring the scattering coefficient of turbid media from two-photon microscopy.

In this paper, we propose a new and simple method based on two-photon excitation fluorescence (TPEF) microscopy to measure the scattering coefficient µ(s) of thick turbid media. We show, from Monte Carlo simulations, that µ(s) can be derived from the axial profile of the ratio of the TPEF signals epi-collected by the confocal and the non-descanned ports of a scanning microscope, independently of the anisotropy factor g and of the absorption coefficient µ(a) of the medium. The method is validated experimentally on tissue-mimicking optical phantoms, and is shown to have potential for imaging the scattering coefficient of heterogeneous media.

Impact of the concentration in polymer on the dynamic behavior of Polymer Stabilized Ferroelectric Liquid Crystal using Snap-shot Mueller Matrix Polarimetry.

Experimental results are presented related to the dynamic behaviour of Polymer Stabilized Ferro-electric Liquid Crystal (PSFLC) samples under external applied electric field, using Snap-shot Mueller Matrix Polarimetry (SMMP) and Mueller Matrix (MM) formalism. Different polarimetric coefficients are simultaneously extracted from each channeled spectrum measured with this full-optical SMMP technique. The impact of the concentration of polymer present into the liquid crystal cell on this dynamic behaviour is studied, permitting a direct and quick characterisation of the material.

Mueller matrix polarimetry for improved liver fibrosis diagnosis.

An experimental Mueller matrix polarimeter is used to quantify human liver fibrosis by measuring retardance and depolarization of thin biopsies. The former parameter is sensitive to fibrillar collagen, the latter is specifically sensitive to fibrillar collagen around blood vessels, which is not significant for liver fibrosis diagnosis. By using depolarization like a filter, retardance distribution enables distinguishing between disease stages and limits the high degree of observer discrepancy.

Time-resolved switching analysis of a ferroelectric liquid crystal by snapshot Mueller matrix polarimetry.

An experimental snapshot Mueller matrix polarimeter based on wavelength polarization coding is used to get a time-resolved description of electric-field-induced fast transition within a ferroelectric liquid-crystal cell. The parameters extracted from experimental Mueller matrices are linked to the molecule director distribution to further determine the average trajectory and the collective behavior of these molecules while they switch over to another state.

Two-channel snapshot Mueller matrix polarimeter.

We describe a new setup for a snapshot Mueller matrix polarimeter (SMMP). It relies on the separation and orthogonal polarization of two light beams by a Wollaston prism located at the setup output. The simultaneous treatment of the two spectra allows an enhancement of accuracy for real-time measurements through reduction of the effects caused by random noise and systematic errors.

Systematic errors specific to a snapshot Mueller matrix polarimeter.

Systematic errors specific to a snapshot Mueller matrix polarimeter are studied. Their origins and effects are highlighted, and solutions for correction and stabilization are proposed. The different effects induced by them are evidenced by experimental results acquired with a given setup and theoretical simulations carried out for more general cases.

Snapshot Mueller matrix polarimeter by wavelength polarization coding.

We present a new, to the best of our knowledge, experimental configuration of Mueller matrix polarimeter based on wavelength polarization coding. This is a compact and fast technique to study polarization phenomena. Our theoretical approach, the necessity to correct systematic errors and our experimental results are presented.