Birefringence Distribution Research Articles

Blood Plasma Film Multifractal Scanning in COVID-19 Consequences Diagnostics.

A 3D phase scanning method was applied to study blood plasma facies, generating layered polarization maps of the object field. The most sensitive parameters to changes in birefringence distribution were identified. Multifractal analysis using wavelet transforms and fractal dimension spectra provided specific insights into the scale self-similarity of the polarization maps. The multifractal spectra of ellipticity distributions were algorithmically derived, revealing that the third- and fourth-order statistical moments were most sensitive to changes in the supramolecular networks of the facies. These findings were successfully applied to differentiate post-COVID-19 effects with high accuracy.

Effect of striae on the high temperature dielectric and electrical properties of lithium aluminosilicate glass-ceramics

Lithium Aluminosilicate glass-ceramics with striae (LAS-WS) and without striae (LAS-WoS) were processed using melt casting technique. LAS-WS and LAS-WoS samples were characterized and found stress birefringence >10 nm/cm and <10 nm/cm, respectively. LAS-WS and LAS-WoS samples were subjected to structural, microstructural, high temperature dielectric and electrical characterization. The presence of striation did not significantly affected the formation of β-spondumene structure during crystallization heat treatment. TEM image confirms the formation of nanocrystals in the glass matrix of lithium aluminosilicate glass-ceramics. The homogeneous distribution of LAS nanocrystals of average size of 3–6 nm is evident from TEM results. Stress birefringence distribution in lithium aluminosilicate glass-ceramic clearly shows the striae formation. Shadowgraphy images confirmed the striae free and striae containing regions in the glass-ceramic. The effect of striae on dielectric properties and AC conductivity was analysed using impedance spectroscopy and it was found that the value of the relative permittivity decreased from 415 (1.2 Hz) to 9.76 (1.2 MHz) for LAS-WoS and from 401 (1.2 Hz) to 10.3 (1.2 MHz) for LAS-WS, respectively. It was found that striae in LAS glass-ceramics influence the electrical impedance and AC conductivity relaxation process rather than relative permittivity. The effect of striae on crystallization and morphology are presented. Both the samples have shown crystallinity of more than 75 %. The electrical conductivity of σ = 2.0 × 10−3 S/cm for LAS-WoS and 2.7 × 10−3 S/cm for LAS-WS at 300 °C as well as σ = 4.6 × 10−3 S/cm for LAS-WoS and 6.9 × 10−3 S/cm for LAS-WS at 700 °C are found to be in good agreement due to increase in the electrical conductivity with temperature. The ionic conductivity of the material due to Li-ion mobility with respect to temperature and electric field and possible mechanism of AC conductivity are discussed. The results presented indicates the potential application of this material that demands high temperature operation of lithium aluminosilicate glass-ceramics.

Polar Decomposition of Jones Matrix and Mueller Matrix of Coherent Rayleigh Backscattering in Single-Mode Fibers.

The Jones matrix and the Mueller matrix of the coherent Rayleigh backscattering (RB) in single-mode fibers (SMFs) have been derived recently. It has been shown that both matrices depict two polarization effects-birefringence and polarization-dependent loss (PDL)-although the SMF under investigation is purely birefringent, having no PDL. In this paper, we aim to perform a theoretical analysis of both matrices using polar decomposition. The derived sub-Jones/Mueller matrices, representing birefringence and PDL, respectively, can be used to investigate the polarization properties of the coherent RB. As an application of the theoretical results, we use the derived formulas to investigate the polarization properties of the optical signals in phase-sensitive optical time-domain reflectometry (φ-OTDR). For the first time, to our knowledge, by using the derived birefringence-Jones matrix, the common optical phase of the optical signal in φ-OTDR is obtained as the function of the forward phase and birefringence distributions. By using the derived PDL-Mueller matrix, the optical intensity of the optical signal in φ-OTDR is obtained as the function of the forward phase and birefringence distributions as well as the input state of polarization (SOP). Further theoretical predictions show that, in φ-OTDR, the common optical phase depends on only the local birefringence in the first half of the fiber section, which is occupied by the sensing pulse, irrelevant of the input SOP. However, the intensity of the φ-OTDR signal is not a local parameter, which depends on the input SOP and the birefringence distribution along the entire fiber section before the optical pulse. Moreover, the PDL measured in φ-OTDR is theoretically proven to be a local parameter, which is determined by the local birefringence and local optical phase distributions.

MULTI-PARAMETER MUELLER-MATRIX TOMOGRAPHY OF HISTOLOGICAL SAMPLES OF BIOLOGICAL TISSUES AS AN ACCURATE AND EFFECTIVE METHOD FOR DETERMINING THE DEGREE OF BLOOD LOSS

Establishing the volume of blood loss is extremely important in the context of forensic practice, as it can indicate various circumstances of death and is important in solving criminal cases. Consideration of modern methods of determining this parameter in the article is relevant and aims to reveal new opportunities and perspectives in this field of forensic medical examination.&#x0D; Aim of the work. To develop a set of new forensic criteria for accurate determination of the volume of blood loss using the method of multichannel polarization Muller-matrix tomography of histological sections of parenchymal organs and human blood samples.&#x0D; Materials and methods. Samples of parenchymal organs and human blood were collected from 76 corpses of both sexes with varying degrees of blood loss from 0 mm3 to 2500 mm3. The research was carried out using the method of multichannel polarization Muller-matrix linear dichroism tomography of biological tissue samples.&#x0D; Results. For all studied biological samples, a decrease in the level of circular birefringence (CB) of formed blood elements against the background of a gradual necrotic decrease in distributions of linear birefringence (LB) of the optical anisotropy of parenchymal tissues and blood films was established for the process of blood loss. The range of sensitivity of the method of differential Mueller-matrix tomography with algorithmic reproduction of linear dichroism maps to changes in blood loss volume of the deceased, which is (0±2000) mm3, is determined.&#x0D; Conclusions. The accuracy of the method of differential Mueller matrix mapping with algorithmic reproduction of linear dichroism maps of biological preparations was determined, which is 86-92 % in the range of the level of blood loss ΔV = (0±2000) mm3.

Design of multi-configuration scanning system for stress birefringence distribution measurement

Design of multi-configuration scanning system for stress birefringence distribution measurement

An Integrated Photoelasticity-Based Approach for the Reconstruction of Stress Profiles and Optical Anisotropy of GRIN Lenses

The paper shows that it is possible to obtain reliable information on the dependence of the radial distribution of longitudinal birefringence in glass cylindrical elements with a radial distribution of refractive index (GRIN lenses) on the basis of transverse polarization tomography data on residual stresses. This does not require complicated procedures of sample preparation, as is necessary in the case of longitudinal translucency measurements. The approach developed was verified in the experiments with a set of different GRIN lenses formed with the ion exchange technique, and the closeness of the data obtained from transversal and conventional longitudinal transmission measurements was demonstrated.

The effect of pupil size on the measurement of corneal birefringence properties: preliminary study

We used a partial Mueller matrix polarimeter to measure the corneal anisotropic properties at three pupil sizes (dilated, natural, and constricted). The geometrical parameters of first order isochromes were described by quadrilaterals. These parameters are statistically significantly different between the three pupil sizes. The pupillary size changes do not influence the azimuth angle distribution α. The retardation R and birefringence distributions show asymmetry in the nasal–temporal cross-section. There are differences between pupil sizes for both nasal and temporal parts of the cornea for these distributions. Iridial light scattering and diffraction might be the reason for these differences.

POSSIBILITIES OF DETERMINING THE TIME SINCE DEATH USING THE METHODS OF MULTIDIMENSIONAL POLARIZATION AND AUTOFLUORESCENCE MICROSCOPY OF THE HUMAN VITREOUS BODY

Given the current state of affairs in practical forensic medicine and the considerable amount of scientific research on the exact determination of the postmortem interval, we conclude that the determination of the time since death is a key problem, but not yet sufficiently solved. Accurately estimating the time since death is critical to many investigations and remains one of the most challenging variables.&#x0D; Carrying out an accurate determination of the time of death is important using a complex approach, since solving this problem requires taking into account all aspects of thanatogenesis, the influence of environmental factors and other circumstances of the case. This leads to an increase in the popularity of global research involving the latest advances in medicine, chemistry, physics and forensics. The use of comprehensive research allows us to come closer to establishing the approximate range of the time since death.&#x0D; Aim of the work. Development of a complex of objective forensic medical criteria to improve the possibilities of accurately determining the time since death over a long period of time by using multidimensional polarization and autofluorescence microscopy of the human vitreous body.&#x0D; Materials and methods. The object of the study were samples of human vitreous body, deceased from cardiovascular pathology, with a known time of death.&#x0D; The following research methods were used: Mueller-matrix mapping, microscopic polarization tomography, spectral-selective laser-induced autofluorescence, statistical and wavelet analysis of the results of experimental data.&#x0D; Results. The significant effectiveness of the proposed methods in accurately determining the time of death has been demonstrated. In particular, polarization microscopic tomography using scale-selective wavelet analysis of distributions of linear birefringence of human vitreousbody layers provides a diagnostic range for determining the time since death of 36 hours with an accuracy of up to 14-16 minutes, which was not achieved by any of the existing laser polarization methods. At the same time, the combination of polarization tomography of biological tissues with spectral-selective laser fluorescence microscopy – one of the most sensitive methods,due to the assessment of the concentration parameters of molecules, opens a new window of possibilities and establishing the time since death and diagnosis of various pathological conditions. The obtained results confirm the effectiveness of this technique and show the diagnostic range of determining the time since death of 36 hours with an accuracy of up to 15-20 minutes.&#x0D; Conclusions. The innovative approach proposed in the scientific study makes a significant contribution to the development of forensic medical examination, providing more accurate and reliable identification of the time since death, which can be useful in criminal investigations and in solving other forensic tasks.

Research on Magnetic-Induced Error of Small-Sized Fiber Optic Gyro Fiber Coil in Space Environment

Spacecraft is severely limited in weight and volume, resulting in a small bending radius of the fiber coil used by IFOG (Interference Fiber Optic Gyroscope). The fiber coil has such a size that the influence of bending on fiber birefringence cannot be ignored. In this paper, we research magnetic-induced errors of small-sized IFOG working in low orbit space. Firstly, we use the Jones matrix to analyze the effects of radial magnetic field and axial magnetic field on IFOG. Secondly, we establish a three-dimensional model for the radial magnetic-induced errors and magnetic-induced errors of minor radius fiber coil. Using the finite element method, we analyze the magnetic-induced error between different levels of the fiber coil. Combined with the birefringence distribution of the minor radius fiber coil, an accurate three-dimensional magnetic-induced error model is established. Thirdly, in the experiment, we design the magnetic-induced error test platform that includes the Fluke standard current source, transconductance amplifier, and Helmholtz coil. The experimental results show that, compared with the traditional calculation method, the three-dimensional magnetic-induced error model reduces the RMSE (Root Mean Square Error) of the radial magnetic field by 56.9% and the RMSE of the axial magnetic field by 35.7%, respectively.

Experimental study of single-shot polarization dynamics of dual dissipative solitons

The state of polarization provides an additional dimension to the pulse dynamics of dissipative solitons. However, due to lack of appropriate measuring instruments, the polarization evolution of dual pulse vector solitons is still unclear. Here, for an erbium-doped fiber laser mode-locked with carbon nanotubes, we characterize the single-shot polarization evolution of dual dissipative solitons in detail using a high-speed wave-resolved measurement technique. For the different birefringence distributions in the laser cavity, the coupling between the orthogonal components of the vector soliton has a great influence on its physical properties, which may lead to various physical images of the vector soliton. We observed typical polarization-locked vector solitons and polarization attractors in the dual soliton pulses. We also observed that the polarization dynamics of the lead and tail vector pulses have similar evolution dynamics on the Poincaré sphere, while they have a distinct phase difference. By virtue of the difference of the processing SOPs between the leading and trailing pulses, we resolve three kinds of two solitons pulses with distinct relative phase evolutions. Our results enrich the vector soliton dynamics in fiber lasers.

Measurement of two-dimensional distribution of stress birefringence based on dual photoelastic modulators cascade difference frequency modulation

Measurement of two-dimensional distribution of stress birefringence based on dual photoelastic modulators cascade difference frequency modulation

A quantitative technique to analyze and evaluate microstructures of skin hair follicles based on mueller matrix polarimetry

In this study, we propose a quantitative technique to analyze and evaluate microstructures of skin hair follicles based on Mueller Matrix transmission microscopy. We measure the Mueller matrix polar decomposition (MMPD) parameter images to reveal the characteristic linear birefringence distribution induced by hair follicles in mouse skin tissue samples. The results indicate that the Mueller matrix-derived parameters can be used to reveal the location and structural integrity of hair follicles. For accurate hair follicle location identification and quantitative structural evaluations, we use the image segmentation method, sliding window algorithm, and image texture analysis methods together to process the Mueller matrix-derived images. It is demonstrated that the hair follicle regions can be more accurately recognized, and their locations can be precisely identified based on the Mueller matrix-derived texture parameters. Moreover, comparisons between manual size measurement and polarimetric calculation results confirm that the Mueller matrix parameters have good performance for follicle size estimation. The results shown in this study suggest that the technique based on Mueller matrix microscopy can realize automatically hair follicle identification, detection, and quantitative evaluation. It has great potential in skin structure-related studies and clinical dermatological applications.

Problems on polarization aberrations in large aperture dynamic interferometry based on the polarization phase shifting technique.

The polarization based phase shifting method is an effective way for dynamic measurements. However, when this technique is applied to the measurements of large optics, the interferometric results are easily limited by the birefringence of large optics. The birefringence changes the polarization states of reference light and test light, and brings constant polarization aberrations into the measurement results independent of the phase shifting procedure. In this article, the detailed theoretical analysis on the mechanism of polarization aberration is presented. Afterwards, we propose a new interferometric method to determine the birefringence effects by measuring the transmitted wavefronts of the large optics, which are considered as birefringent samples. Theoretical analysis shows that the polarization error in the linearly polarized system can be corrected by two independent measurements with orthogonal polarization states. The phase retardance can be obtained from the wavefront difference of the transmitted wavefronts when switching the polarization states of the incident lights. The birefringence distribution obtained is used to calibrate the polarization aberrations in the measurement result of a homemade large aperture measurement platform and the correction result is compared with the result via the wavelength tuning phase shifting method. The elimination of the polarization aberrations can be observed in the final results.

Shear Rate Imaging Using A Polarization Camera And A Birefringent Aqueous Cellulose Nanocrystal Suspension

Two aqueous cellulose nanocrystal suspensions are used to experimentally measure the shear and strain rates in a two-dimensional fluid flow. Cellulose nanocrystals are rod-like particles that align when subjected to shear, whereas at rest, they are randomly orientated by Brownian motion. The alignment causes birefringence, a phenomenon also known as flow-induced birefringence. The amount of birefringence is measured using a rotatable linear polarizer and a polarization camera. The linear polarizer is rotated to nine different positions. At each position, light from a light source becomes linear polarized before entering the birefringent fluid. Because of the birefringence the state of polarization is changed. This change is measured by the polarization camera. From the nine measurements the two-dimensional birefringence distribution is determined and from the amount of birefringence the strain rate is derived with the help of the data published by Lane et al. (2022a). We define Λ_0 as the angle between the (maximum) strain rate and the direction of flow. A shearing flow leads to Λ_0=45°, whereas Λ_0=0° and Λ_0=90° describe a flow down the centerline of a symmetrically converging and diverging channel, respectively. The measured strain rates are compared to simulations. The reference data in (Lane et al., 2022a) was taken at Λ_0=45°. For Λ_0≈45°, measurements and simulations correspond well to each other. If Λ_0≈0° is assumed, measured strain rates appear too high whereas they are too low for Λ_0≈90°. These results may be of interest for two reasons. First, shear rate imaging gave satisfying results in areas where Λ_0≈45°. Therefore, we propose the study of shear rates in a two-dimensional shearing flow by means of the presented method. Second, the results indicate that the flow state affects the degree of particle alignment and thus birefringence. This finding is in line with the statements made by Wayland (1960, 1964). The study of particle alignment and its influencing factors is of interest, and the experimental approach presented here is thought to be practicable for such studies.

Optical evaluation of a double-layered ultrasound liquid crystal lens

A method to improve the performance of an ultrasound liquid crystal lens is proposed. A double-layer-based lens model tailored based on the liquid crystal’s physical properties, e.g., its dielectric anisotropy and elastic constants, is presented as an alternative method to improve the lens’s optical performance while forming weak anchoring surfaces for nematic liquid crystals, thus promoting easier reorientation of the liquid crystal molecules. The lens configuration was simulated by finite-element analysis using Ansys software. The lens’s physical and optical characteristics were evaluated via comparison using two different liquid crystal materials: 5CB and RDP-85475. The birefringence distribution within the liquid crystal layer was investigated under ultrasound excitation, and the molecular angles of inclination were estimated. A higher birefringence distribution, greater molecular inclination, and a longer focal length were obtained for the double-layered liquid crystal lens using the 5CB material.

Orientation and Residual Stress Distributions in Thick Melt Spun Polystyrene and Polycarbonate Filaments

Abstract A study of orientation development and residual stresses in thick melt spun polystyrene filaments and polycarbonate filaments described. Linear relationships between spinline stress and mean birefringence under different melt spinning conditions were obtained. These results were used together with models of the dynamics of melt spinning to predict the characteristics of thick melt spun filaments. Birefringence distrbutions and residual stresses were computed. High orientations and compressive circumferential residual stresses were predicted at the larger radii and low orientation and tensile circumferential and radial residual stress in the fiber core are obtained. The distribution of birefringence across the thickness of thick melt spun filaments was measured by determining changes of retardation across a wedge. The birefringence distributions were correlated with severity of quench and model prediction. Thick melt spun fibers were peeled and found to have fibrillar cores.

Spectral analysis of Brillouin dynamic gratings in polarization-maintaining fibers.

Experiment observations show that the spectra of Brillouin dynamic gratings in polarization-maintaining fibers based on a polarization decoupled scheme are quite broad and usually have multiple peaks. In this paper, we measure the birefringence distribution along polarization-maintaining fibers with high spatial resolution using optical frequency-domain reflectometry. Based on birefringence measurements, both the simulation and experiment are carried out to determine the spectra of Brillouin dynamic gratings generated within the same polarization-maintaining fibers, indicating quantitatively that spectral broadening and irregularity are mainly due to phase mismatch caused by the non-uniformity of birefringence along polarization-maintaining fibers.

Research on the Birefringence Distribution of the Fiber Coil With Quadrupole Symmetrical Winding Method

As the core component of the fiber optic gyroscope, the fiber coil has been the focus of research. In the field of fiber coil environmental adaptability research, researchers are calculating environmental errors, such as thermally-induced errors and magnetic-induced errors. They approximated the refractive index and birefringence of the fiber coil to an average value. However, the values of birefringence changes by the different bending radius of the fibers in the different layers, which would greatly reduce the accuracy of the environment error model. Therefore, in this paper, a birefringence distribution model of the fiber coil is proposed for the first time based on the quadrupole symmetrical winding pattern. Firstly, we qualitatively analyze the birefringence of Panda-type polarization-maintaining fiber, and then the fiber coil winding law is established through detailed analysis of the standard quadrupole symmetric winding method. Secondly, we use the finite element method to analyze the force of the single-layer fiber, and obtain the change law of the refractive index of polarization-maintaining fiber. The mathematical model of the birefringence distribution is established and simulated. Finally, we use optical coherence domain polarization measurement technology to detect the distributed polarization crosstalk of the fiber coil. The data is obtained by using the white light interferometer that is consistent with the simulation. The result proves the correctness of the theory. Moreover, an experimental platform for Sagnac loop is built, and the interference optical power is measured by the optical spectrum analyzer. Compared with the equivalent radius method, the accuracy of model is improved by 91.48% at 1310nm.The method proposed in this paper will greatly promote the research on the environmental adaptability of fiber optic gyroscope.

PM-PCF birefringence distribution measurement over a wide wavelength range based on SSFS and LSSI.

A linear self-reference spectral interferometry has been proposed to measure the distribution of polarization-maintaining photonic crystal fiber (PM-PCF) birefringence over a wide wavelength range combined with the soliton self-frequency shift and birefringence effect. The birefringence of PM-PCF is measured experimentally over the range of 800-970 nm, which is larger than 5×10-4 and shows a segmented change trend. The air micropore structure has a significant effect on the characteristics of PM-PCF, which makes it have a highly nonlinear coefficient, and at the same time, changes the dispersion and birefringence distributions of the PM-PCF. The distribution of PM-PCF birefringence, measured by experiment, provides a new dimension for the design of PM-PCF, which is helpful for a detailed fiber model and an iterative optimization of fiber structure.

Birefringent properties of the cornea measured by a Mueller type polarimeter in healthy adults and children.

Mueller type polarimeter was used for in vivo measurements of the anisotropic parameters (retardation and azimuth angle) of corneas. To determine birefringence, corneal thickness was measured with a Scheimpflug camera (Corvist ST). The retardation distributions in the nasal-temporal cross-section in both children (N=7) and adults (N=38) groups occurred asymmetrical. The asymmetry in birefringence distributions was observed only in adults group. The geometrical analysis of the first order isochromes in both age groups showed the asymmetry of its shapes. The changes of symmetry in birefringent properties with age may have potential relationship with changing corneal biometry.