Birefringence Analysis Research Articles

Birefringence Analysis of Photonic-Bandgap Fibers Using the Hexagonal Yee's Cell

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A full-vectorial finite-difference scheme utilizing the hexagonal Yee's cell is used in this paper to analyze the modes of photonic-bandgap fibers with <formula formulatype="inline"><tex Notation="TeX">${\rm C}_{6v}$</tex> </formula> symmetry. Because it respects the fiber's native symmetry, this method is free from any numerical birefringence. We also incorporate in it techniques for reducing the memory requirement (up to 3 to 4 times) and computational time, in particular by exploiting some of the symmetry properties of these fibers. Using sub-pixel averaging, we demonstrate quadratic convergence for the fundamental mode's effective index dependence on spatial resolution. We show that this method can be used to calculate the beat length of PBFs in which a birefringence is introduced by applying a small unidirectional stretch to the fiber cross section along one of its axes. Abrupt variations of the modeled fiber geometries with spatial resolution lead to oscillatory beat length convergence behavior. We can obtain a better estimate for beat length by averaging these oscillations. We apply a strong perturbation analysis to the fiber's unperturbed mode, calculated by our finite-difference method, to perform this averaging in a rigorous way. By fitting a polynomial to the predicted beat lengths as a function of grid spacing, we obtain an accurate estimate of the beat length at zero grid spacing. Reasonable convergence for the beat length is observed using a single processor with 8 GB of memory. </para>

Terahertz imaging: applications and perspectives

Terahertz (THz) spectroscopy, and especially THz imaging, holds large potential in the field of nondestructive, contact-free testing. The ongoing advances in the development of THz systems, as well as the appearance of the first related commercial products, indicate that large-scale market introduction of THz systems is rapidly approaching. We review selected industrial applications for THz systems, comprising inline monitoring of compounding processes, plastic weld joint inspection, birefringence analysis of fiber-reinforced components, water distribution monitoring in polymers and plants, as well as quality inspection of food products employing both continuous wave and pulsed THz systems.

Analysis of photoinduced birefringence in azo-dye doped films by a fast imaging technique

In photo-birefringent films, the relationship ρ( I) between optical retardation ρ and pump irradiance I may be obtained with imaging techniques applied within a pump–probe setup. However, measurement of ρ( I) are reported only at long irradiation times and low time-resolution. In this paper we describe a polariscopic imaging technique with higher sensitivity (by a factor of ∼ 30), where the probe beam is focused on the entrance pupil of the camera (“Maxwellian view”). The technique is applied to an azo-dye doped polymeric film, obtaining the continuous ρ( I) curve after irradiation times from 10 ms to 240 ms. Exponential functions are fitted against the experimental data both as a function of time and irradiance.

Quantifying strain birefringence halos around inclusions in diamond

The pressure and temperature conditions of formation of natural diamond can be estimated by measuring the residual stress that an inclusion remains under within a diamond. Raman spectroscopy has been the most commonly used technique for determining this stress by utilising pressure-sensitive peak shifts in the Raman spectrum of both the inclusion and the diamond host. Here, we present a new approach to measure the residual stress using quantitative analysis of the birefringence induced in the diamond. As the analysis of stress-induced birefringence is very different from that of normal birefringence, an analytical model is developed that relates the spherical inclusion size, Ri, host diamond thickness, L, and measured value of birefringence at the edge of the inclusion, to the peak value of birefringence that has been encountered; to first order. From this birefringence, the remnant pressure (Pi) can be calculated using the photoelastic relationship, where qiso is a piezo-optical coefficient, which can be assumed to be independent of crystallographic orientation, and n is the refractive index of the diamond. This model has been used in combination with quantitative birefringence analysis with a MetriPol system and compared to the results from both Raman point and 2D mapping analysis for a garnet inclusion in a diamond from the Udachnaya mine (Russia) and coesite inclusions in a diamond from the Finsch mine (South Africa). The birefringence model and analysis gave a remnant pressure of 0.53 ± 0.01 GPa for the garnet inclusion, from which a source pressure was calculated as 5. 7 GPa at 1,175°C (temperature obtained from IR analysis of the diamond host). The Raman techniques could not be applied quantitatively to this sample to support the birefringence model; they were, however, applied to the largest coesite inclusion in the Finsch sample. The remnant pressure values obtained were 2. 5 ± 0.1 GPa (birefringence), 2.5 ± 0.3 GPa (2D Raman map), and 2.5-2.6 GPa (Raman point analysis from all four inclusions). However, although the remnant pressures from the three methods were self-consistent, they led to anomalously low source pressure of 2.9 GPa at 1,150°C (temperature obtained from IR analysis) raising serious concerns about the use of the coesite-in-diamond geobarometer. © 2010 Springer-Verlag.

Modeling and analysis of birefringence in magneto-optical thin film made by SiO2/ZrO2 doped with ferrite of cobalt

The zero-birefringence condition is an important requirement for magneto-optical waveguide devices. It has been analyzed by means of Film Mode Matching method (FMM). The modelling is based on geometrical adjustments of the rib waveguide and especially the etch depth, which is a critical parameter in the design of rib waveguide. We determine the waveguide dimensions that would allow the same propagation constants for both polarizations TE and TM, and we have found that there are more choices for waveguide dimensions to produce birefringence-free waveguides and single-mode rib waveguide simultaneously.

Polarized Light Microscopic Analysis of Bone Formation After Inhibition of Cyclooxygenase 1 and 2

Potassium diclofenac is a potent nonsteroidal anti-inflammatory drug (NSAID) and COX isoforms (COX-1 and COX-2) inhibitor. Quantitative analysis of birefringence with polarized light microscopy is a useful method to investigate the macromolecular orientation and organization of collagen fibers in connective tissues. The aim of this research was to analyze the collagen structure and maturation in bone formed after potassium diclofenac administration, during first molar orthodontic movement. Sixty Wistar rats were divided in two equal groups (N = 30): control (C) and potassium diclofenac (PD). The animals in Group C received 0.9% saline solution and the PD group received potassium diclofenac Cataflam (5 mg/kg). Animals were sacrificed 3, 7, or 14 days after a NiTi unilateral closed-coil spring was stretched between the upper right first molar and the incisors. The first molar area was fixed, decalcified, and histologically processed using picrosirius pigment. The collagen birefringence of bone turnover was analyzed by phase retardation. Two-way ANOVA and Tukey's test showed that optical retardation was influenced by time and treatment. There was increase in the collagen organization over time. On the third day, the C group showed better collagen organization than the PD group. Potassium diclofenac interfered in collagen maturation, reducing fibril organization in the initial phase of orthodontic movement.

1701 ArFエキシマレーザー光源用フッ化カルシウム単結晶チャンバウィンドウの使用環境下における複屈折解析(OS17. 電子デバイス・電子材料と計算力学(1),オーガナイズドセッション講演)

1701 ArFエキシマレーザー光源用フッ化カルシウム単結晶チャンバウィンドウの使用環境下における複屈折解析(OS17. 電子デバイス・電子材料と計算力学(1),オーガナイズドセッション講演)

The role of the matrix-filler affinity on morphology and properties of polyethylene/clay and polyethylene/ compatibilizer/clay nanocomposites drawn fibers

AbstractIn this work the structural variations and mechanical performance of polyethylene/clay nanocomposite drawn fibres, also in the presence of compatibilizer, such as a commercial maleic anhydride grafted polyethylene, PEgMA, was studied. In the isotropic state both systems show intercalated morphology.After spinning and cold drawing, by adding the nanoparticles, the tensile strength as a function of the draw ratio increases and this rise is more pronounced for the filled compatibilized system. The reduction of the elongation at break, on the contrary, is about the same for all the examined samples. The orientation of the macromolecules, evaluated by measurements of the birefringence and calorimetric analysis, is similar for all the samples, but the filled, drawn fibres show a higher level of intercalation and, in particular, some exfoliation, more and more pronounced with the draw ratio and in presence of compatibilizer, as a consequence of the application of the extensional (at low and high temperature) flow. For the three components system with greater affinity between the polymer matrix and clay, the extensional flow is more efficient. The initial intercalated morphology changes to some more intercalation and finally, at the highest anisotropic condition in the presence of the PEgMA, evolves to delaminated clay structure.

A comparative analysis of the zona pellucida birefringence of fresh and frozen–thawed human embryos

The cryopreservation of human embryos is thought to induce alteration in the glycoprotein matrix and lead to zona change. However, this assumption has been full of controversies till now. The objective of this study was to evaluate the effect of cryopreservation on zona pellucida of human embryos. Fresh (n=106, from 40 patients) and frozen-thawed embryos (n=123, from 40 patients) were obtained from consenting patients who received conventional IVF and ICSI treatment. The birefringence of zona pellucida in human fresh and frozen-thawed embryos was imaged and quantitatively analyzed using polarized light microscopy before embryo transfer. There was no significant difference in retardance and thickness of the zona pellucida multilaminar structure between the two groups. Pregnancy and implantation rates of transferred fresh and frozen-thawed embryos were also compared. No significant difference was found in the rates of clinical pregnancy (47.5 vs 37.5%) and implantation (24.5 vs 23.2%) between the two groups. This study suggests that there is no significant change in the zona pellucida birefringence of human embryos before and after cryopreservation.

Comparative Studies of Crystalline Orientation and Morphology of Injection Molded Polyolefin Parts

Abstract We have studied the structural characteristics of the cross-sections of injection molded parts of various crystalline polyolefins including polyethylene (PE), isotactic polypropylene (PP), isotactic poly(butene-1) (PB1) and isotactic poly(4-methylpentene-1) (P4MP1). Polarized light microscopy, birefringence and wide angle x-ray diffraction pole figure analysis were used to investigate the samples. In most cases, high orientations were observed near the mold wall and isotropic molded part cores were found. However, highly oriented mold core regions were found in P4MP1. Significantly different types of crystalline orientation near the mold wall were observed among the various polyolefins. We represent the development of these differences through the components of a crystalline orientation tensor which represent changes in the state of orientation between melts in the mold prior to crystallization and the final crystalline molded part.

Birefringence simulation of annealed ingot of magnesium fluoride single crystal

We developed a method for simulating birefringence of an annealed ingot of MgF 2 single crystal for lithography optics. This method provides the optical path difference caused by crystal symmetry and residual stress existing in the crystal. The method consists of the heat conduction analysis, the residual stress analysis and the birefringence analysis. Because there exists no experimental data on the inelastic behavior of MgF 2 single crystal, the residual stress was estimated with the elastic thermal stress analysis using the finite element method by assuming a stress-free temperature. In this analysis, the temperature dependence of material properties and crystal anisotropy were taken into account. In the birefringence analysis, the distributions of optical path difference were calculated by an approximate method using the result of the residual stress analysis. This approximate method uses the average stress along the wave normal and is equivalent to the exact method in case of low stress dealt with the present study. In this analysis, it is possible to consider both the intrinsic birefringence and the stress birefringence in any crystal orientation. The distribution of the optical path difference in the annealed ingot obtained from the present calculation agrees qualitatively with that of the experiment. Its calculated value also agrees reasonably well with that of the experiment, when a stress-free temperature is adequately selected.

Phase-matched pure χ^(3) third-harmonic generation in noncentrosymmetric BiB_3O_6

Third-harmonic generation (THG) has been investigated in the monoclinic BiB(3)O(6). The symmetry and birefringence analysis revealed that there are phase-matching conditions for the direct third-order nonlinear process, where the cascading second-order processes are precluded by the zero effective nonlinearity. The first phase-matched pure chi((3)) THG in a noncentrosymmetric crystal is presented together with the improved Sellmeier and thermo-optic dispersion formulas.

Birefringence analysis in photonic crystal fibers with germanium-doped core

We present the results of numerical analysis of birefringence in photonic crystal fibers with germanium-doped inclusions in the core. In such fibers, geometrical birefringence induced by holey cladding interplays with the birefringence induced by shape and composition of doped inclusions. The latter gives rise also to stress birefringence associated with different thermal expansion coefficients in doped and non-doped regions. In our analysis, we consider elliptical and circular inclusions and demonstrate that, by proper selection of the inclusions' geometry, it is possible to increase significantly the phase modal birefringence to a level greater than 10−4 in the short wavelength range. Moreover, it is possible to shape the dispersion of the phase modal birefringence in such a way that the group birefringence crosses zero value at a certain wavelength.

Relationship between dermal birefringence and the skin surface roughness of photoaged human skin

The dermal degeneration accompanying photoaging is considered to promote skin roughness features such as wrinkles. Our previous study demonstrated that polarization-sensitive spectral domain optical coherence tomography (PS-SD-OCT) enabled noninvasive three-dimensional evaluation of the dermal degeneration of photoaged skin as a change in dermal birefringence, mainly due to collagenous structures. Our purpose is to examine the relationship between dermal birefringence and elasticity and the skin morphology in the eye corner area using PS-SD-OCT. Nineteen healthy male subjects in their seventees were recruited as subjects. A transverse dermal birefringence map, automatically produced by the algorithm, did not show localized changes in the dermal birefringence in the part of the main horizontal wrinkle. The averaged upper dermal birefringence, however, showed depth-dependent correlation with the parameters of skin roughness significantly, suggesting that solar elastosis is a major factor for the progress of wrinkles. Age-dependent parameters of skin elasticity measured with Cutometer did not correlate with the parameters. These results suggest that the analysis of dermal birefringence using PS-SD-OCT enables the evaluation of photoaging-dependent upper dermal degeneration related to the change of skin roughness.

SKS splitting measurements beneath Northern Apennines region: A case of oblique trench-retreat

We present here the new observations of seismic anisotropy obtained from SKS birefringence analysis. We studied 27 teleseismic earthquakes recorded by the temporary seismic network of RETREAT project in the Northern Apennines region. For each station–event couple we calculate the anisotropic parameters (delay time and fast-polarization direction) by minimizing the energy in the transverse component. Our measurements confirm the existence of two domains. The Tuscany domain, on the south-west with respect to the Apennines, shows mostly NW–SE fast axes directions, with a rotation toward E–W direction moving toward the Tyrrhenian Sea. The Adria domain, north-east of the Apennines orogen, shows more scattered measurements, with prevailing N–S to NNE–SSW directions, also with back-azimuthal dependence. The transition between the two domains is abrupt in the northern part of the study region but more gradual in the southern part. Measured delay times (1.8 s on average) suggest that the detected anisotropy is located principally in the asthenosphere. Beneath the Adria domain, where the presence of a double-layer structure seems consistent, a lithospheric contribution is plausible. An interpretation in terms of ongoing mantle deformation suggests a differential evolution of the trench-retreat process along the Northern Apennines orogen. The orogen-parallel anisotropy in the study region is beneath the inner part of the belt instead of beneath its crest and no orogen-normal measurements are found in the Tuscany side. Compared to the anisotropy pattern of the typical slab retreat seen in southern part of the Northern Apennines, in the northernmost one the anisotropy suggests that an oblique trench-retreat has occurred, possibly linked to Northern Apennines retreat since 5 Ma.

In vivo Three-Dimensional Birefringence Analysis Shows Collagen Differences between Young and Old Photo-Aged Human Skin

Polarization-sensitive optical coherence tomography (PS-OCT) permits non-invasive visualization of dermal birefringence, mainly due to collagenous structures. The purpose of this study is to use PS-OCT to assess intrinsic-age-related and photo-age-related differences in three-dimensional dermal birefringence. We measured dermal birefringence of the cheek skin and photo-protected interior upper arm skin from old and young volunteers. The algorithm that we used automatically produces the transversal dermal birefringence map from the polarization-sensitive OCT volume. This allowed quantitative comparison and visualization of the transverse distribution of the dermal birefringence. We found that dermal birefringence of the cheek skin was significantly smaller in the old group than in the young group (young group, 0.295+/-0.037 degrees microm(-1); old group, 0.207+/-0.03 degrees microm(-1); P=0.003), whereas the interior upper arm showed no age-dependent difference. The transversal map of the cheek showed a heterogeneous decrease in dermal birefringence due to photoaging. The maps suggested that the peripheral regions of some infundibula were surrounded by a strong collagen network. Three-dimensional analyses of dermal birefringence using PS-OCT help to quantify the diagnosis of photoaging.

Performance analysis of intracavity birefringence sensing

The performance of intracavity birefringence sensing by use of a standing-wave laser is theoretically analyzed when the cavity involves internal reflection. On the three-mirror compound cavity model, the condition for converting an optical path length into a laser frequency or a retardation into an optical beat frequency with good linearity and little uncertainty is derived as a function of the cavity parameters and is numerically analyzed.

Optical Anisotropy of Supported Lipid Structures Probed by Waveguide Spectroscopy and Its Application to Study of Supported Lipid Bilayer Formation Kinetics

Supramolecular conformation and molecular orientation was monitored during supported lipid bilayer (SLB) formation using dual polarization interferometry (DPI). DPI was shown to enable real time sensitive determination of birefringence of the lipid bilayer together with thickness or refractive index (with the other a fixed value). This approach removes differences in mass loading due to anisotropy, so the mass becomes solely a function of the lipid d n/d c value. DPI measurements show highly reproducible qualitative and quantitative results for adsorption of liposomes of different lipid compositions and in buffers with or without CaCl 2. The packing of solvent-free self-assembled SLBs is shown to differ from other preparation methods. Birefringence analysis accompanied by mass and thickness measurements shows characteristic features of vesicle adsorption and SLB formation kinetics previously not demonstrated by evanescent optical techniques, including indications of percolation-type rupture of clusters of liposomes on the surface and correlated adsorption kinetics induced by liposome charge repulsion. Our study demonstrates that understanding of mechanistic details for an adsorption process for which conformational changes and ordering occur can be elucidated using DPI and greatly enhanced by modeling of optical birefringence. The data is in some respects more detailed than what can be obtained with conventional biosensing techniques like surface plasmon resonance and complementary to methods such as the quartz crystal microbalance.

Stress distribution and induced birefringence analysis for pressure vector sensing based on single mode fibers

We propose a theoretical approach to analyze the pressure stress distribution in single mode fibers (SMFs) and achieve the analytical expression of stress function, from which we obtain the stress components with their patterns in the core and compute their induced birefringence. Then we perform a pressure vector sensing based on approximately 2 km SMF. Using Mueller matrix method we measure the birefringence vectors which are employed to compute the pressure magnitudes and their orientation. When rotating the pressure around the fiber, the corresponding birefringence vector rotates around a circle with double speed. Statistics show the average deviation of calculated pressure-magnitude to practical value is approximately 0.17 N and it is approximately 0.85 degrees for orientation.

Biglycan Is Required for Adaptive Remodeling After Myocardial Infarction

After myocardial infarction (MI), extensive remodeling of extracellular matrix contributes to scar formation and preservation of hemodynamic function. On the other hand, adverse and excessive extracellular matrix remodeling leads to fibrosis and impaired function. The present study investigates the role of the small leucine-rich proteoglycan biglycan during cardiac extracellular matrix remodeling and cardiac hemodynamics after MI. Experimental MI was induced in wild-type (WT) and bgn(-/0) mice by permanent ligation of the left anterior descending coronary artery. Biglycan expression was strongly increased at 3, 7, and 14 days after MI in WT mice. bgn(-/0) mice showed increased mortality rates after MI as a result of frequent left ventricular (LV) ruptures. Furthermore, tensile strength of the LV derived from bgn(-/0) mice 21 days after MI was reduced as measured ex vivo. Collagen matrix organization was severely impaired in bgn(-/0) mice, as shown by birefringence analysis of Sirius red staining and electron microscopy of collagen fibrils. At 21 days after MI, LV hemodynamic parameters were assessed by pressure-volume measurements in vivo to obtain LV end-diastolic pressure, end-diastolic volume, and end-systolic volume. bgn(-/0) mice were characterized by aggravated LV dilation evidenced by increased LV end-diastolic volume (bgn(-/0), 111+/-4.2 microL versus WT, 96+/-4.4 microL; P<0.05) and LV end-diastolic pressure (bgn(-/0), 24+/-2.7 versus WT, 18+/-1.8 mm Hg; P<0.05) and severely impaired LV function (EF, bgn(-/0), 12+/-2% versus WT, 21+/-4%; P<0.05) 21 days after MI. Biglycan is required for stable collagen matrix formation of infarct scars and for preservation of cardiac hemodynamic function.