Journal articles: 'Birefringence'

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Wang, Ning, and Xiao Xia Li. "The Electrically Controlled Birefringence Measurement Influence of Liquid Crystal Caused by Absorption Effect in Infrared Region." Advanced Materials Research 875-877 (February 2014): 467–71. http://dx.doi.org/10.4028/www.scientific.net/amr.875-877.467.

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The electrically controlled birefringence of nematic liquid crystal BL-009 was measured by polarized interference method. The influence of LC absorption effect, the birefringence variation, is discussed in this paper. The experiments results showed the influence to birefringence is big in infrared region. Not only the birefringence value is greatly different with that of unconsidering absorption effect, but also the gradient changing of birefringence curves is obvious. Furthermore, the electrically controlled birefringences of two conditions are compared when the absorption coefficients of ordinary light and the extraordinary light are nearly same and greatly different. The analysis demonstrated the approximate method of absorption coefficient is feasible.

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Afsharan, Hadi, Dilusha Silva, Chulmin Joo, and Barry Cense. "Non-Invasive Retinal Blood Vessel Wall Measurements with Polarization-Sensitive Optical Coherence Tomography for Diabetes Assessment: A Quantitative Study." Biomolecules 13, no. 8 (August 8, 2023): 1230. http://dx.doi.org/10.3390/biom13081230.

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Diabetes affects the structure of the blood vessel walls. Since the blood vessel walls are made of birefringent organized tissue, any change or damage to this organization can be evaluated using polarization-sensitive optical coherence tomography (PS-OCT). In this paper, we used PS-OCT along with the blood vessel wall birefringence index (BBI = thickness/birefringence2) to non-invasively assess the structural integrity of the human retinal blood vessel walls in patients with diabetes and compared the results to those of healthy subjects. PS-OCT measurements revealed that blood vessel walls of diabetic patients exhibit a much higher birefringence while having the same wall thickness and therefore lower BBI values. Applying BBI to diagnose diabetes demonstrated high accuracy (93%), sensitivity (93%) and specificity (93%). PS-OCT measurements can quantify small changes in the polarization properties of retinal vessel walls associated with diabetes, which provides researchers with a new imaging tool to determine the effects of exercise, medication, and alternative diets on the development of diabetes.

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Winterstein, Donald F., Gopa S. De, and Mark A. Meadows. "Twelve years of vertical birefringence in nine‐component VSP data." GEOPHYSICS 66, no. 2 (March 2001): 582–97. http://dx.doi.org/10.1190/1.1444950.

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Since 1986, when industry scientists first publicly showed data supporting the presence of azimuthal anisotropy in sedimentary rock, we have studied vertical shear‐wave (S-wave) birefringence in 23 different wells in western North America. The data were from nine‐component vertical seismic profiles (VSPs) supplemented in recent years with data from wireline crossed‐dipole logs. This paper summarizes our results, including birefringence results in tabular form for 54 depth intervals in 19 of those 23 wells. In the Appendix we present our conclusions about how to record VSP data optimally for study of vertical birefringence. We arrived at four principal conclusions about vertical S-wave birefringence. First, birefringence was common but not universal. Second, birefringence ranged from 0–21%, but values larger than 4% occurred only in shallow formations (<1200 m) within 40 km of California’s San Andreas fault. Third, at large scales birefringence tended to be blocky. That is, both the birefringence magnitude and the S-wave polarization azimuth were often consistent over depth intervals of several tens to hundreds of meters but then changed abruptly, sometimes by large amounts. Birefringence in some instances diminished with depth and in others increased with depth, but in almost every case a layer near the surface was more birefringent than the layer immediately below it. Fourth, observed birefringence patterns generally do not encourage use of multicomponent surface reflection seismic data for finding fractured hydrocarbon reservoirs, but they do encourage use of crossed‐dipole logs to examine them. That is, most reservoirs were birefringent, but none we studied showed increased birefringence confined to the reservoir.

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Bai, Zhiyong, Chun-Li Hu, Dongmei Wang, Lehui Liu, Lizhen Zhang, Yisheng Huang, Feifei Yuan, and Zhoubin Lin. "[Al(H2O)6](IO3)2(NO3): a material with enhanced birefringence induced by synergism of two superior functional motifs." Chemical Communications 56, no. 78 (2020): 11629–32. http://dx.doi.org/10.1039/d0cc04813e.

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A new strongly birefringent material was developed, and its strong birefringence was attributed to the synergy of the effects of its two superior birefringence-favourable anionic FBUs, namely (NO₃)⁻ and (IO₃)⁻ groups.

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Chen, Jianbang, Mengfan Wu, Jie Zhang, and Xuchu Huang. "Linear unit BN₂: a novel birefringence-enhanced fundamental module with sp orbital hybridization." RSC Advances 12, no. 23 (2022): 14757–64. http://dx.doi.org/10.1039/d2ra02135h.

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The linear unit BN2 is discovered as a novel birefringence-enhanced fundamental module. Particularly, Ca3(BN2)N exhibits a large birefringence (0.411 at 1064 nm), which is about 2.0–3.5 times of the commercial used birefringent crystals, such as α-BaB2O4, CaCO3 and YVO4.

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Li, Jian Hua, Fei Huang, Yi Yang, Bao Fu Zhang, and Hua Zhou. "High Birefringent Terahertz Photonic Crystal Fiber Based on Material-Filled Structure." Applied Mechanics and Materials 462-463 (November 2013): 599–603. http://dx.doi.org/10.4028/www.scientific.net/amm.462-463.599.

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A novel kind of high birefringent terahertz (THz) photonic crystal fibers (PCFs) with material-filled structure is proposed in this paper. Based on the material-filled technology, which different materials are selectively filled into four air holes of the inner first circle near the central core in the designed THz PCFs, high birefringence are obtained from the structural and material-filled induced asymmetry in large frequency ranges near 1THz. Modal birefringence with different structural parameters and diverse refractive indices of the filled materials are investigated by plane wave expansion (PWE) method. The numerical results show that high birefringence up to 10-3can be obtained and its structure is simpler than that of the early proposed highly birefringent THz PCFs. It is helpful for PCFs design and real fabrication in the potential THz applications.

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Ohkita, H., A. Tagaya, and Y. Koike. "Synthesis of a Zero-Birefringence Polymer Doped with an Inorganic Birefringent Crystal." Solid State Phenomena 99-100 (July 2004): 143–48. http://dx.doi.org/10.4028/www.scientific.net/ssp.99-100.143.

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Birefringence induced by the orientation of polymer main chains during injectionmoulding or extrusion processing restricts the application of optical polymers to optical devices that require the polarization state of incident light to be maintained. To compensate this birefringence of polymers we propose using the “birefringent crystal dopant method” - homogeneous doping with an opposite birefringent needle-like crystal. Strontium carbonate (SrCO3) was selected for this purpose and synthesized, with a length of about 200nm and a width of about 20nm. SrCO3 was doped into poly(MMA/BzMA= 78/22(wt./wt.)) film. The film was uniaxially drawn at 130°C and 4mm/min. For the first time, the positive birefringence of the drawn copolymer film at a wavelength of 633nm was compensated by doping with 0.3wt.% of SrCO3 without loss of transparency and thermostability.

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Tiner, J. D. "Birefringent Spores Differentiate Encephalitozoon and Other Microsporidia from Coccidia." Veterinary Pathology 25, no. 3 (May 1988): 227–30. http://dx.doi.org/10.1177/030098588802500307.

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Tissue sections containing protozoa with birefringent spores indicate an infection by microsporidia. Hematoxylin and cosin (HE) does not affect spore birefringence, but some special stains (Goodpasture, Brown and Brenn, or Gram) obscure it. Encephalitozoon cuniculi from an infected puppy, Glugea stephani from the winter flounder Pseudopleuronectes americanus. and Plistophora sp. from the Japanese eel Anguilla japonica all have birefringent spores. Encephalitozoon was studied first and then the two genera from fishes were included for comparison. Small masses of newly formed spores (pseudocysts) line Glugea cysts and then merge into the contents of the cyst as it enlarges and bulges through the intestinal musculature to become subserosal. The birefringence of Plistophora is present in fully mature spores contained in pseudocysts, but may disappear when the spores are released and become involved in granulomas. Coccidians from various hosts were always non-birefringent. Whenever a protozoan organism in a tissue could be either microsporidian or coccidian, a test for birefringence, if positive, resolves the question. There may be no need to use a special stain.

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Wang, Jinhui, Xinyuan Zhang, Fei Liang, Zhanggui Hu, and Yicheng Wu. "Co-crystal AX·(H3C3N3O3) (A = Na, Rb, Cs; X = Br, I): a series of strongly anisotropic alkali halide cyanurates with a planar structural motif and large birefringence." Dalton Transactions 50, no. 33 (2021): 11555–61. http://dx.doi.org/10.1039/d1dt02217b.

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Zeng, Jian Hui, Xu You Li, and Wen Bin Hu. "A Novel High-Birefringent Photonic Crystal Fiber and its Polarization Maintaining Properties." Advanced Materials Research 760-762 (September 2013): 185–89. http://dx.doi.org/10.4028/www.scientific.net/amr.760-762.185.

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A novel high-birefringent photonic crystal fiber (PCF) was proposed and analyzed by full-vector finite element method (FEM). The modal field and birefringence properties were investigated. All of air holes in proposed PCF are round, and their diameters are the same. It is greatly reduce the difficulty of fabrication. According to the results of numerical analysis, it can be observed that the mode birefringence of this novel PCF can be easily achieve the order of 10-3at 1.55μm. This research provides effective theoretical method for the fabrication, development and construction of high-birefringence photonic crystal fiber.

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Abghari, Arefe, Raelyn M. Sullivan, Lukas T. Hergt, and Douglas Scott. "Constraints on cosmic birefringence using E-mode polarisation." Journal of Cosmology and Astroparticle Physics 2022, no. 08 (August 1, 2022): 033. http://dx.doi.org/10.1088/1475-7516/2022/08/033.

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Abstract A birefringent universe could show itself through a rotation of the plane of polarisation of the cosmic microwave background photons. This is usually investigated using polarisation B modes. Here we point out an independent method for extracting the birefringence angle using only temperature and E-mode signals. We forecast that, with an ideal cosmic-variance-limited experiment, we could constrain a birefringence angle of 0.3° with 3σ statistical significance, which is close to the current constraints using B modes. We explore how this method is affected by the systematic errors introduced by the polarisation efficiency. In the future, this could provide an additional way of checking any claimed B-mode derived birefringence signature.

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Mutailipu, Miriding, Min Zhang, Bingbing Zhang, Zhihua Yang, and Shilie Pan. "The first lead fluorooxoborate PbB5O8F: achieving the coexistence of large birefringence and deep-ultraviolet cut-off edge." Chemical Communications 54, no. 49 (2018): 6308–11. http://dx.doi.org/10.1039/c8cc02694g.

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Kefer, Stefan, Tobias Limbach, Natalie Pape, Kathrin Klamt, Bernhard Schmauss, and Ralf Hellmann. "Birefringence in Injection-Molded Cyclic Olefin Copolymer Substrates and Its Impact on Integrated Photonic Structures." Polymers 16, no. 2 (January 5, 2024): 168. http://dx.doi.org/10.3390/polym16020168.

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This contribution quantifies the birefringence within injection-molded cyclic olefin copolymer plates and discusses its impact on the mechanical properties of the plates. It also focuses on the impact of birefringence on integrated waveguides and Bragg gratings and provides fabrication guidelines for such structures. The anisotropy in all three dimensions of the workpiece is examined by means of polarimetry and a prism coupler. It is found that the birefringence is inhomogenously distributed within the workpieces, whereas the maximum birefringence not only varies locally, but also depends on the observation direction. Overall, a maximum birefringence of 10 × 10−4 is found at the plate’s surface near the injection gate. The anisotropy then reduces exponentially towards the center of the workpiece and saturates at 1.8 × 10−4, in a depth of 0.4 mm. Thus, the birefringence strongly affects near-surface photonic structures. It is found that, depending on their orientation and the local birefringence of the substrate, waveguides and Bragg gratings fabricated with comparable parameters behave completely differently in terms of polarization-dependent optical attenuation, cross-sectional intensity distribution and Bragg reflection signal. For example, the support of the TM mode can vary between total loss and an optical attenuation of 0.9 dB × cm−1. In consequence, this study underlines the importance of quantifying the birefringent state of an injection-molded cyclic olefin copolymer workpiece if it is supposed to serve as a substrate for integrated photonic structures. The study furthermore demonstrates that birefringence effects can be omitted by burying the photonic structures deeper into the volume of the thermoplastic.

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Chen, Xinglong, Fangfang Zhang, Yunjing Shi, Yanzhou Sun, Zhihua Yang, and Shilie Pan. "MBaYB6O12(M = Rb, Cs): two new rare-earth borates with large birefringence and short ultraviolet cutoff edges." Dalton Transactions 47, no. 3 (2018): 750–57. http://dx.doi.org/10.1039/c7dt04223j.

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Kwon, Oh-Tae, Geonwoo Kim, Hyungjin Bae, Jaeyeol Ryu, Sikwan Woo, and Byoung-Kwan Cho. "Development of a Mercury Bromide Birefringence Measurement System Based on Brewster’s Angle." Sensors 23, no. 9 (April 23, 2023): 4208. http://dx.doi.org/10.3390/s23094208.

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Mercury bromide (Hg2Br2) has been used to develop acousto-optic tunable filters (AOTFs) because it has several advantages, including a high refractive index, a broad optical bandwidth, and a relatively high figure of merit. Therefore, the measurement of its birefringence is a highly important factor for ensuring AOTF quality. However, for single crystals, it is difficult (at the millimeter scale) to quantify the birefringence using an ellipsometer, as this equipment is only designed to conduct measurements on thin films. In this study, a simple birefringence measurement system for Hg2Br2 was developed based on Brewster’s angle at the millimeter scale. The planar distributions of the Hg2Br2 crystal along the (100), (010), and (001) planes were used in the experiments. The developed measurement system can measure the reflected light intensity of the Hg2Br2 crystal depending on the incidence angles (rotations at 0.01125° steps) and can calculate the ordinary and extraordinary refractive indices and birefringence. The calculated birefringence of the Hg2Br2 crystal was 0.8548; this value exhibits an error of 0.64% compared with a value of 0.86 reported in the literature. The developed measurement system demonstrates the ability to be used to evaluate the quality of birefringent single crystals.

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Ademgil, Huseyin. "Highly birefringent large mode area photonic crystal fiber-based sensor for interferometry applications." Modern Physics Letters B 30, no. 36 (December 30, 2016): 1650422. http://dx.doi.org/10.1142/s0217984916504224.

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In this work, highly birefringent large mode area (LMA) photonic crystal fiber (PCF) structure for interferometric sensor applications is proposed. The effective mode area, birefringence and the sensitivity coefficient of the proposed PCF structure by employing the full vectorial finite element method (FV-FEM) have been thoroughly investigated. The numerical results have shown that proposed structure simultaneously offers high birefringence of order 10[Formula: see text], adequately LMA and high sensitivity for various liquid analytes by employing the elliptical liquid core holes.

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Liu, Shuo, Yuanwei Li, Rui Ma, Linwan Zhao, Jiaqi lv, and Xiaolong Dong. "Study on the High-Birefringence Hollow-Core Anti-Resonant Fiber with Semicircular Cladding." International Journal of Optics 2021 (May 21, 2021): 1–10. http://dx.doi.org/10.1155/2021/5520142.

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For the purpose of satisfying the demands of polarization-maintaining fibers for fiber optic gyroscopes, this article proposes a semicircular cladding birefringent hollow-core anti-resonant fiber. The influence of structural parameters on the birefringence, loss, and bending loss of the fiber is studied. The simulation results demonstrate that at 1550 nm, the ultimate loss of the fundamental mode of x and y polarization is 1.76 dB/m and 0.93 dB/m, respectively. The birefringence can reach 1 × 10−4, and the wavelength range of birefringence greater than 10−4 can reach 60 nm. This indicates that it has excellent bending properties. The proposed optical fiber has excellent performance in polarization maintenance and can supply ideas for the research of high-precision fiber optic gyroscopes and other optical devices.

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Tian, Jing, Heng Yao, Maxime Cavillon, Enric Garcia-Caurel, Razvigor Ossikovski, Michel Stchakovsky, Celine Eypert, Bertrand Poumellec, and Matthieu Lancry. "A Comparison between Nanogratings-Based and Stress-Engineered Waveplates Written by Femtosecond Laser in Silica." Micromachines 11, no. 2 (January 24, 2020): 131. http://dx.doi.org/10.3390/mi11020131.

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This paper compares anisotropic linear optical properties (linear birefringence, linear dichroism, degree of polarization) and performances (absorption coefficient, thermal stability) of two types of birefringent waveplates fabricated in silica glass by femtosecond laser direct writing. The first type of waveplate is based on birefringence induced by self-organized nanogratings imprinted in the glass. One the other hand, the second design is based on birefringence originating from the stress-field formed around the aforementioned nanogratings. In addition to the provided comparison, the manufacturing of stress-engineered half waveplates in the UV-Visible range, and with mm-size clear aperture and negligible excess losses, is reported. Such results contrast with waveplates made of nanogratings, as the later exhibit significantly higher scattering losses and depolarization effects in the UV-Visible range.

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Dong, Hui, Hailiang Zhang, and Dora Juan Juan Hu. "Polar Decomposition of Jones Matrix and Mueller Matrix of Coherent Rayleigh Backscattering in Single-Mode Fibers." Sensors 24, no. 6 (March 8, 2024): 1760. http://dx.doi.org/10.3390/s24061760.

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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.

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Clark, Alexander T., Sophia D’Anna, Jessy Nemati, Phillip Barden, Ian Gatley, and John Federici. "Evaluation of Fossil Amber Birefringence and Inclusions Using Terahertz Time-Domain Spectroscopy." Polymers 14, no. 24 (December 15, 2022): 5506. http://dx.doi.org/10.3390/polym14245506.

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Using a cross-polarization transmission geometry, stress maps for the normalized birefringence and intrinsic stress direction of polymeric materials may be obtained using terahertz nondestructive evaluation. The analysis method utilizes a deconvolution method to determine the arrival times and amplitude of the cross-polarized terahertz pulses through a birefringent material. Using amber (a naturally occurring polymer) as a material of interest, stress maps show that inclusion-free Lebanese amber samples behave as classic uniaxial birefringent (photoelastic) materials whose principal stress directions, as inferred in the terahertz spectral range, agree well with visible photoelasticity measurements. Since amber samples, depending upon their source, may be either transparent or opaque to visible light, comparing birefringence measurements in the visible and terahertz spectral ranges cross-validates the stress measurements, thereby establishing a strong and unique stress analysis methodology for visibly opaque samples. While the material of interest for this paper is amber, the method is generally applicable for any terahertz-transparent polymer. The cross-polarization experimental configuration enables stress levels within the amber matrix to be visualized while also outlining highly localized regions of stress surrounding inclusions. Birefringence stress maps clearly show localized increases in stress magnitude and directional changes surrounding inclusions.

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Lin, Samuel I. En. "Stress Birefringence in Photonic Crystal Fibers Used in a Novel Field Installable LC Type Optical Connector." Key Engineering Materials 364-366 (December 2007): 404–7. http://dx.doi.org/10.4028/www.scientific.net/kem.364-366.404.

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Photonic crystal fibers (PCFs) have recently attracted a great deal of interest because of their unique characteristics and many controllable features. They include a wide range of single mode operation, highly birefringent characteristics (~10-3), high-power light transmission, etc. The field-installable LC connectors tend to be of the larger connector types in the fiber-to-the-home (FTTH) distribution units. In these designs, fibers are clamped inside a splice assembly and are stressed within the connector. In this research, we first developed a novel cam-type mechanism for field-use LC connector. The fiber stress was analyzed via a commercial available finite element program. The stress birefringence distributions of single mode fiber and air-silica based PCFs were calculated by stress photoelastic effect. We further studied the effect of air-hole size on the stressinduced birefringence of PCFs. The results indicate that stress-induced birefringence decreases as air-hole size increase. On the other hand, the birefringence increases as applied clamping force increases on the single mode fiber.

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Rumpa, Ramin Chapa. "Ultra-High Birefringence Property and Low Confinement Loss of Circular Photonic Crystal Fiber for Telecommunication Application." International Journal for Research in Applied Science and Engineering Technology 12, no. 3 (March 31, 2024): 3366–81. http://dx.doi.org/10.22214/ijraset.2024.58219.

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Abstract: A redesigned PCF structure with minimal confinement loss and high birefringence is proposed in this research paper. It employs a circular lattice arrangement with one ring of identical air holes. High birefringence and low confinement loss are two of the properties that have been numerically studied using the finite element method with circular perfectly matched layer boundary conditions. By adjusting the hole size and spacing, it is possible to achieve both properties simultaneously. At an excitation wavelength of 1550 nm, a numerically obtained modal birefringence of 2.3179×10-2 is observed. Simultaneously, by methodically evaluating the cladding rings, the center-to-center distance between the air holes, and the number of cladding rings with equal diameters, a minimal confinement loss (<10-1) may be achieved. Additionally, the suggested PCF verifies that it is feasible to acquire. Our extremely birefringent fiber can be controllably created thanks to the development of birefringence with structural modifications. The suggested structure has better optical characteristics, making it a potential contender for sensing and broadband dispersion correction.

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Heyl, Jeremy, and Ilaria Caiazzo. "Strongly Magnetized Sources: QED and X-ray Polarization." Galaxies 6, no. 3 (July 21, 2018): 76. http://dx.doi.org/10.3390/galaxies6030076.

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Radiative corrections of quantum electrodynamics cause a vacuum threaded by a magnetic field to be birefringent. This means that radiation of different polarizations travels at different speeds. Even in the strong magnetic fields of astrophysical sources, the difference in speed is small. However, it has profound consequences for the extent of polarization expected from strongly magnetized sources. We demonstrate how the birefringence arises from first principles, show how birefringence affects the polarization state of radiation and present recent calculations for the expected polarization from magnetars and X-ray pulsars.

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Tan, Melissa, Alexander T. Martin, Alexander G. Shtukenberg, and Bart Kahr. "Tuning the optical isotropic point of mixed crystals of ethylenediammonium sulfate/selenate." Journal of Applied Crystallography 53, no. 1 (February 1, 2020): 51–57. http://dx.doi.org/10.1107/s1600576719015863.

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In anisotropic crystals, optical isotropic points are wavelengths where linear birefringence disappears because the refractive indices for both eigenmodes are accidentally equivalent. Here, the optical isotropic point of ethylenediammonium selenate (EDSe) is tuned by generating a solid-solution series of EDSe doped with sulfate. Mueller matrix polarimetry and single-crystal X-ray diffraction are used to correlate changes in linear birefringence with the crystal composition of EDS x Se1−x . A scheme for using mixed crystals with isotropic points as tunable birefringent optical bandpass filters is proposed and their performance is modeled.

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KIM, AHYOUNG, J. W. WU, S. H. HAN, BYOUNGCHOO PARK, and HIDEO TAKEZOE. "ELECTRO-OPTIC AND ELECTRO-GYRATION EFFECTS IN CHIRAL MOLECULAR SYSTEMS." Journal of Nonlinear Optical Physics & Materials 13, no. 03n04 (December 2004): 397–404. http://dx.doi.org/10.1142/s0218863504002018.

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The linear electro-optic (EO) and electro-gyration (EG) effects are studied in an optically active material systems including Bi 12 SiO 20 (BSO) oxide and bent-core liquid crystals. In an isotropic BSO sample, the breaking of intrinsic centro-symmetry allowed the EO modulation of the refractive index. In a mixture of bent-shaped liquid crystalline molecules having both optical activity and birefringence, the observed intensity modulation is investigated, which is related to the nonlinear optical responses of both the optical rotatory power and the birefringence. Both the linear EO and EG effects are understood in terms of the superposition principle of linear and circular birefringences.

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Fan, Hua, Meguya Ryu, Reo Honda, Junko Morikawa, Zhen-Ze Li, Lei Wang, Jovan Maksimovic, Saulius Juodkazis, Qi-Dai Chen, and Hong-Bo Sun. "Laser-Inscribed Stress-Induced Birefringence of Sapphire." Nanomaterials 9, no. 10 (October 3, 2019): 1414. http://dx.doi.org/10.3390/nano9101414.

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Birefringence of 3 × 10 - 3 is demonstrated inside cross-sectional regions of 100 μ m, inscribed by axially stretched Bessel-beam-like fs-laser pulses along the c-axis inside sapphire. A high birefringence and retardance of λ / 4 at mid-visible spectral range (green) can be achieved using stretched beams with axial extension of 30–40 μ m. Chosen conditions of laser-writing ensure that there are no formations of self-organized nano-gratings. This method can be adopted for creation of polarization optical elements and fabrication of spatially varying birefringent patterns for optical vortex generation.

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Huband, S., D. S. Keeble, N. Zhang, A. M. Glazer, A. Bartasyte, and P. A. Thomas. "Crystallographic and optical study of LiNb1 − xTaxO3." Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 73, no. 3 (June 1, 2017): 498–506. http://dx.doi.org/10.1107/s2052520617004711.

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Powders of lithium niobate-tantalate across the full compositional range have been made and crystals grown using a lithium vanadate flux growth technique. The Li-content of a lithium tantalate crystal has been determined using the zero-birefringence temperature and Curie measurements, confirming the Li content is between that of congruent and stoichiometric crystals. X-ray diffraction measurements show the Nb/Ta displacement and octahedral tilt both decrease as the Ta content is increased. This also results in a decrease in the lattice parameters from lithium niobate to lithium tantalate. Birefringence measurements on the crystals as a function of temperature have been used to determine the point that the crystals become zero-birefringent, and by comparison with the structural studies have confirmed that it is not related to a phase transition and the structures remain polar through the zero-birefringence points.

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Tang, Ru-Ling, Xin Lian, Wen-Dong Yao, Wenlong Liu, and Sheng-Ping Guo. "K₃Na(TaF₇)(SiF₆): a mixed-anion pentanary fluoride with zero-dimensional anions exhibiting a large band gap." Dalton Transactions 50, no. 45 (2021): 16562–67. http://dx.doi.org/10.1039/d1dt03320d.

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A pentanary fluoride K3Na(TaF7)(SiF6) having a zero-dimensional anionic framework representing a new type of chemical composition and structure exhibits a large band gap and larger birefringence compared to the commercial birefringent crystal MgF2.

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Greco, Alessandro, Nicola Bartolo, and Alessandro Gruppuso. "Cosmic birefrigence: cross-spectra and cross-bispectra with CMB anisotropies." Journal of Cosmology and Astroparticle Physics 2022, no. 03 (March 1, 2022): 050. http://dx.doi.org/10.1088/1475-7516/2022/03/050.

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Abstract Parity-violating extensions of Maxwell electromagnetism induce a rotation of the linear polarization plane of photons during propagation. This effect, known as cosmic birefringence, impacts on the Cosmic Microwave Background (CMB) observations producing a mixing of E and B polarization modes which is otherwise null in the standard scenario. Such an effect is naturally parametrized by a rotation angle which can be written as the sum of an isotropic component α 0 and an anisotropic one δα(n̂). In this paper we compute angular power spectra and bispectra involving δα and the CMB temperature and polarization maps. In particular, contrarily to what happens for the cross-spectra, we show that even in absence of primordial cross-correlations between the anisotropic birefringence angle and the CMB maps, there exist non-vanishing three-point correlation functions carrying signatures of parity-breaking physics. Furthermore, we find that such angular bispectra still survive in a regime of purely anisotropic cosmic birefringence, which corresponds to the conservative case of having α o = 0. These bispectra represent an additional observable aimed at studying cosmic birefringence and its parity-violating nature beyond power spectrum analyses. They provide also a way to perform consistency checks for specific models of cosmic birefringence. Moreover, we estimate that among all the possible birefringent bispectra,〈δαTB〉and〈δαEB〉are the ones which contain the largest signal-to-noise ratio. Once the cosmic birefringence signal is taken to be at the level of current constraints, we show that these bispectra are within reach of future CMB experiments, as LiteBIRD.

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Kudryashov, Sergey, Alexey Rupasov, Roman Zakoldaev, Mikhail Smaev, Aleksandr Kuchmizhak, Alexander Zolot’ko, Michail Kosobokov, Andrey Akhmatkhanov, and Vladimir Shur. "Nanohydrodynamic Local Compaction and Nanoplasmonic Form-Birefringence Inscription by Ultrashort Laser Pulses in Nanoporous Fused Silica." Nanomaterials 12, no. 20 (October 15, 2022): 3613. http://dx.doi.org/10.3390/nano12203613.

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The inscription regimes and formation mechanisms of form-birefringent microstructures inside nano-porous fused silica by tightly focused 1030- and 515-nm ultrashort laser pulses of variable energy levels and pulsewidths in the sub-filamentary regime were explored. Energy-dispersion X-ray micro-spectroscopy and 3D scanning confocal Raman micro-spectroscopy revealed the micro-tracks compacted by the multi-shot laser exposure with the nanopores hydrodynamically driven on a microscale to their periphery. Nearly homogeneous polarimetrically acquired subwavelength-scale form-birefringence (refractive index modulation ~10−3) was simultaneously produced as birefringent nanogratings inside the microtracks of wavelength-, energy- and pulsewidth-dependent lengths, enabling the scaling of their total retardance for perspective phase-modulation nanophotonic applications. The observed form-birefringence was related to the hierarchical multi-scale structure of the microtracks, envisioned by cross-sectional atomic-force microscopy and numerical modeling.

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Sukharenko, Vitaly, and Roger Dorsinville. "Polarization Sensitive Imaging with Qubits." Applied Sciences 12, no. 4 (February 15, 2022): 2027. http://dx.doi.org/10.3390/app12042027.

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We compare reconstructed quantum state images of a birefringent sample using direct quantum state tomography and inverse numerical optimization technique. Qubits are used to characterize birefringence in a flat transparent plastic sample by means of polarization sensitive measurement using density matrices of two-level quantum entangled photons. Pairs of entangled photons are generated in a type-II nonlinear crystal. About half of the generated photons interact with a birefringent sample, and coincidence counts are recorded. Coincidence rates of entangled photons are measured for a set of sixteen polarization states. Tomographic and inverse numerical techniques are used to reconstruct the density matrix, the degree of entanglement, and concurrence for each pixel of the investigated sample. An inverse numerical optimization technique is used to obtain a density matrix from measured coincidence counts with the maximum probability. Presented results highlight the experimental noise reduction, greater density matrix estimation, and overall image enhancement. The outcome of the entanglement distillation through projective measurements is a superposition of Bell states with different amplitudes. These changes are used to characterize the birefringence of a 3M tape. Well-defined concurrence and entanglement images of the birefringence are presented. Our results show that inverse numerical techniques improve overall image quality and detail resolution. The technique described in this work has many potential applications.

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Inoue, Tadashi, Kazuyuki Fujiwara, Deug-Soo Ryu, Kunihiro Osaki, Michiaki Fuji, and Kazuo Sakurai. "Viscoelasticity and Birefringence of Low Birefringent Polyesters." Polymer Journal 32, no. 5 (May 2000): 411–14. http://dx.doi.org/10.1295/polymj.32.411.

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Lane, C., F. Baumann, and T. Rösgen. "Shear Rate Imaging Using A Polarization Camera And A Birefringent Aqueous Cellulose Nanocrystal Suspension." Proceedings of the International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics 20 (July 11, 2022): 1. http://dx.doi.org/10.55037/lxlaser.20th.140.

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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.

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Wang, Xiu Ping, and Zhong Jiao He. "Highly Birefringent Extruded Elliptical-Hole Photonic Crystal Fiber." Advanced Materials Research 663 (February 2013): 387–91. http://dx.doi.org/10.4028/www.scientific.net/amr.663.387.

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Highly birefringent extruded elliptical-hole photonic crystal fibers (PCFs) with single defect and double defect are proposed and investigated, which are supposed to be achieved by extruding conventional triangular-lattice circular-hole PCFs. Comparative research on the birefringence and the confinement loss of the proposed PCFs with single defect and double defect is presented. Simulated results show that the proposed extruded elliptical-hole PCFs with single defect and double defect can be with high birefringence up to the order of 10-2. Confinement loss increases when the ellipticity of the air hole of the proposed PCFs increases, which nevertheless can be overcome by increasing the ring number or the area of the air holes in the fiber cladding.

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Wójcik, Waldemar, Zhengbing Hu, Yuriy Ushenko, Andrzej Smolarz, Iryna Soltys, Oleksander Dubolazov, Oleksander Ushenko, et al. "Optical Sensor System for 3D Jones Matrix Reconstruction of Optical Anisotropy Maps of Self-Assembled Polycrystalline Soft Matter Films." Sensors 24, no. 5 (February 29, 2024): 1589. http://dx.doi.org/10.3390/s24051589.

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Our work uses a polarization matrix formalism to analyze and algorithmically represent optical anisotropy by open dehydration of blood plasma films. Analytical relations for Jones matrix reconstruction of optical birefringence maps of protein crystal networks of dehydrated biofluid films are found. A technique for 3D step-by-step measurement of the distributions of the elements of the Jones matrix or Jones matrix images (JMI) of the optically birefringent structure of blood plasma films (BPF) has been created. Correlation between JMI maps and corresponding birefringence images of dehydrated BPF and saliva films (SF) obtained from donors and prostate cancer patients was determined. Within the framework of statistical analysis of layer-by-layer optical birefringence maps, the parameters most sensitive to pathological changes in the structure of dehydrated films were found to be the central statistical moments of the 1st to 4th orders. We physically substantiated and experimentally determined the sensitivity of the method of 3D polarization scanning technique of BPF and SF preparations in the diagnosis of endometriosis of uterine tissue.

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Cristoforetti, Alessandro, Michela Masè, and Flavia Ravelli. "Model-Based Approach for the Semi-Automatic Analysis of Collagen Birefringence in Polarized Light Microscopy." Applied Sciences 13, no. 5 (February 24, 2023): 2916. http://dx.doi.org/10.3390/app13052916.

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Collagen is a key determinant of physio-pathological processes in different tissues. Polarization light microscopy (PLM) of histological sections is the gold-standard for birefringence-based collagen quantification, but post-session image analysis can be time-consuming and subjective. We propose an efficient semi-automatic computational approach for the quantification of collagen content from the analysis of PLM images of birefringent histological sections. The method is based on a physical model of light-sample interaction and birefringence effect production. It combines the information of bright and dark-field PLM images to segment the luminal region and detect the birefringent signal associated with collagen in the tissue region. User input is limited to the selection of a threshold on an image subset and the supervision of the processing, enabling fast analysis of large datasets. Modeling of the birefringence signal compensates for variability factors related to sample processing and image acquisition, such as section thickness variability and nonuniform illumination and transmittance. As a proof-of-concept, the method was applied to human cardiac tissue PLM images, acquired in 14 cardiac surgery patients with different arrhythmic profiles. The method was able to detect a significantly larger amount and higher heterogeneity of fibrosis in the atrium of patients with as opposed to without atrial fibrillation (p < 0.05). The proposed method can be a valid aid to quicken and reinforce the analysis of large sets of PLM images for the quantification of collagen distribution in different tissues and pathologies.

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van Houten, H., W. A. von Marinelli, and J. J. M. Beenakker. "An Upper Limit for Birefringence in the Boundary Layer of a Heat Conducting Gas." Zeitschrift für Naturforschung A 40, no. 2 (February 1, 1985): 164–68. http://dx.doi.org/10.1515/zna-1985-0210.

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The Waldmann-Vestner theory for boundary layer effects in polyatomic gases in the nearhydrodynamic regime predicts that in a rarefield heat conducting gas the boundary layers will be birefringent due to the presence of second rank angular momentum polarization. An experiment has been set up in order to measure the birefringence as a function of the distance to the boundary. However, no effect could be detected for N2 and C02 within the sensitivity of the experiment. This corresponds to an upper limit for the birefringence, which is a factor 6 smaller than expected. These results are in contrast to the qualitative data reported earlier in the literature; no conclusions can be drawn, however, about the validity of the Waldmann-Vestner theory.

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De Araújo, H. P., and S. G. Dos Santos Filho. "Characterization of Birefringent Titanium-Oxide Thin Films Deposited by DC Sputtering." Journal of Integrated Circuits and Systems 12, no. 1 (December 28, 2017): 42–46. http://dx.doi.org/10.29292/jics.v12i1.449.

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This work presents the characterization of birefringent properties of titanium-oxide thin films using spectrophotometry and double-cavity Fabry-Perot structures. All films were deposited by DC sputtering over tilted substrates and the birefringence was characterized as a function of the deposition angle by the numerical difference between the refractive indexes for s- and p-polarized light beams. As a result, the highest value of birefringence (0.03) was obtained for samples tilted at 21º (having the normal axis as reference). A polarizing narrow-band Fabry-Perot filter centered at 400 and 700nm was designed by means of numerical simulations of the multilayer structures using a MATLAB© toolbox to solve the classical optical equations. Using this designed double-cavity Fabry-Perot structure [Ag(40nm) / TiO2(160nm) / Ag(40nm) / TiO2(164nm) / Ag(40nm)], transmittance ratios (Tp/Ts) for p- and s-polarized light beams resulted 1.70 at a wavelength of 699nm and 1.36 at another wavelength of 393nm (centers of the two narrow-band peaks), which corroborated the birefringent characteristics of the nearly-stoichiometric titania (TiO2) thin films.

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THATCHER, M. J., and M. J. MORGAN. "BIREFRINGENT ELECTROWEAK DEFECTS." International Journal of Modern Physics A 17, no. 14 (June 10, 2002): 1953–64. http://dx.doi.org/10.1142/s0217751x02010583.

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In this paper we examine the propagation of electromagnetic waves through electroweak textures and W-strings. The photon is associated with a negative mass squared term as a consequence of its coupling to the intermediate vector bosons from which the electroweak defect is constructed. The photon pseudo-mass depends on the polarization of the photon and results in electroweak defects exhibiting birefringent properties. We calculate the effective refractive index and birefringence length scale. The cosmological implications of birefringent electroweak defects are discussed.

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Slepkov, Aaron D. "Quantitative measurement of birefringence in transparent films across the visible spectrum." American Journal of Physics 90, no. 8 (August 2022): 625–34. http://dx.doi.org/10.1119/5.0087798.

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Common transparent polymer films, such as cellophane and household tape, are frequently used as examples of birefringent materials in textbooks and classroom demonstrations. Qualitatively, birefringence is often demonstrated by layering such films between crossed-polarizers. In this work, we describe an inexpensive experimental setup for the quantitative measurement of birefringence in common household films, suitable for senior high school or undergraduate labs. Whereas traditional approaches for polarization-based classroom experiments typically use monochromatic laser light, we encourage the combined use of an incoherent incandescent light source and a portable spectrometer. In addition, we demonstrate how any concomitant thin-film interference effects can be used to separately measure the optical thickness in the most heterogeneous and uniform films. Such measurement can then be used as an independent experimental confirmation of either the film's index of refraction or its thickness, given knowledge of the other. In an effort to provide examples for the data analysis procedures as well as to investigate a range of materials, we measure the birefringence across the visible spectrum of six common household polymer films, including thin kitchen wrap, cellophane, gift basket film, and common adhesive tapes.

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Li, Peng-Fei, Chun-Li Hu, Fang Kong, Shao-Ming Ying, and Jiang-Gao Mao. "Y2(Te4O10)(SO4): a new sulfate tellurite with a unique Te4O10 polyanion and large birefringence." Inorganic Chemistry Frontiers 8, no. 1 (2021): 164–72. http://dx.doi.org/10.1039/d0qi01130d.

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Y₂(Te₄O₁₀)(SO₄), featuring a unique (Te₄O₁₀)⁴⁻ polyanion, exhibits a large birefringence (0.124@1064), wide energy band gap (4.1 eV) and high thermal stability (>700 °C), which make it a potential birefringent material.

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Sharma, Mohit, Vaishali Dixit, S. Konar, Kawsar Ahmed, and Vigneswaran Dhasarathan. "Endlessly single-mode photonic crystal fiber with high birefringence for sensing applications." Modern Physics Letters B 34, no. 06 (January 31, 2020): 2050077. http://dx.doi.org/10.1142/s0217984920500773.

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A novel type of highly birefringent photonic crystal fiber is designed, which yields to promise a very large birefringence [Formula: see text] with flat dispersion at the operating wavelength 1550 nm. By employing the FDTD method, other properties, such as dispersion, walk-off effect and [Formula: see text]-parameters, are highly optimized using lattice period of air holes.

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Real, Eusebio, José Icardo, Gaspar Fernández-Barreras, José Revuelta, Marta Calvo Díez, Alejandro Pontón, José Gutiérrez, José López Higuera, and Olga Conde. "Identification of Human Pathological Mitral Chordae Tendineae Using Polarization-sensitive Optical Coherence Tomography." Sensors 19, no. 3 (January 28, 2019): 543. http://dx.doi.org/10.3390/s19030543.

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Defects of the mitral valve complex imply heart malfunction. The chordae tendineae (CTs) are tendinous strands connecting the mitral and tricuspid valve leaflets to the papillary muscles. These CTs are composed of organized, wavy collagen bundles, making them a strongly birefringent material. Disorder of the collagen structure due to different diseases (rheumatic, degenerative) implies the loss or reduction of tissue birefringence able to be characterized with Polarization Sensitive Optical Coherence Tomography (PS-OCT). PS-OCT is used to discriminate healthy from diseased chords, as the latter must be excised and replaced in clinical conventional interventions. PS-OCT allows to quantify birefringence reduction in human CTs affected by degenerative and rheumatic pathologies. This tissue optical property is proposed as a diagnostic marker for the identification of degradation of tendinous chords to guide intraoperative mitral valve surgery.

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Tsuchida, Satoshi, and Hiroshi Kuratsuji. "Stochastic theory of polarized light in nonlinear birefringent media: An application to optical rotation." International Journal of Modern Physics B 32, no. 12 (May 3, 2018): 1850147. http://dx.doi.org/10.1142/s0217979218501473.

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A stochastic theory is developed for the light transmitting the optical media exhibiting linear and nonlinear birefringence. The starting point is the two-component nonlinear Schrödinger equation (NLSE). On the basis of the ansatz of “soliton” solution for the NLSE, the evolution equation for the Stokes parameters is derived, which turns out to be the Langevin equation by taking account of randomness and dissipation inherent in the birefringent media. The Langevin equation is converted to the Fokker–Planck (FP) equation for the probability distribution by employing the technique of functional integral on the assumption of the Gaussian white noise for the random fluctuation. The specific application is considered for the optical rotation, which is described by the ellipticity (third component of the Stokes parameters) alone: (i) The asymptotic analysis is given for the functional integral, which leads to the transition rate on the Poincaré sphere. (ii) The FP equation is analyzed in the strong coupling approximation, by which the diffusive behavior is obtained for the linear and nonlinear birefringence. These would provide with a basis of statistical analysis for the polarization phenomena in nonlinear birefringent media.

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Peters, Winfried S., Reinhard Schnetter, and Michael Knoblauch. "Research note: Reversible birefringence suggests a role for molecular self-assembly in forisome contractility." Functional Plant Biology 34, no. 4 (2007): 302. http://dx.doi.org/10.1071/fp06281.

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Forisomes are contractile protein bodies that control the effective diameter of the sieve elements of the faboid legumes by reversible, Ca2+-driven changes of shape. Forisomes consist of fibrils; we inferred from available electron-microscopical data (which necessarily provide images of fixed, non-functional forisomes) that a reversible assembly of ordered fibrillar arrays might be involved in the contractile mechanism. Here we examined functional forisomes isolated from Vicia faba L. by differential interference contrast microscopy and polarisation microscopy. We found them birefringent in the longitudinally expanded but not in the contracted state, showing ‘parallel extinction’ with the direction of vibration of the slow ray coinciding with their long axis (positive birefringence). These findings met predictions derived from the theory of form birefringence in rodlet composite bodies, and supported the idea of molecular self-assembly as a factor in forisome contractility.

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Chiang, K. S., D. Wong, and P. L. Chu. "Strain-induced birefringence in a highly birefringent optical fibre." Electronics Letters 26, no. 17 (1990): 1344. http://dx.doi.org/10.1049/el:19900866.

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NOVAC, B. M., I. R. SMITH, and M. C. ENACHE. "Considerations of pressure induced birefringence in highly birefringent fibres." International Journal of Electronics 86, no. 8 (August 1999): 1031–35. http://dx.doi.org/10.1080/002072199133012.

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Dorohoi, Dana Ortansa, Mihai Postolache, Cristina Delia Nechifor, Dan Gheorghe Dimitriu, Raluca Marinica Albu, Iuliana Stoica, and Andreea Irina Barzic. "Review on Optical Methods Used to Characterize the Linear Birefringence of Polymer Materials for Various Applications." Molecules 28, no. 7 (March 26, 2023): 2955. http://dx.doi.org/10.3390/molecules28072955.

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Optical polymers are recognized for their high transparency, raised flexibility, low cost, and good film-forming ability; hence, they introduce a multitude of benefits in a wide range of devices, such as information storage, displays, optical communications, and filters. Among the optical properties, birefringence is an essential parameter in practical cases that demand the control of the state of polarization of light. This review is focused on describing some fundamental and applicative aspects concerning the optical birefringence of the polymer materials. First, elementary notions depicting the phenomenon of light double refraction in macromolecular media are provided. Furthermore, the most relevant optical techniques to determine birefringence are reviewed by highlighting the working principle and mathematical basis for computing this parameter. Then, a series of investigations of optically birefringent polymers are described, summarizing the most utilized approaches to induce light double refraction in such materials. The selected results are analyzed in relation to the pursued applications. In the end, the future of this scientific domain is briefly presented by establishing the research paths that need further exploration. Moreover, the novel directions that could be formulated and might contribute to certain considerable advancements in the materials employed in the modern optical technologies are mentioned.

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Sigaev, V. N., A. S. Lipatiev, S. S. Fedotov, S. V. Lotarev, A. S. Naumov, and D. M. Shevyakina. "POLARIZATION CONTROLLED BIREFRINGENCE IN LITHIUM ALUMINOSILI-CATE GLASS." Steklo i Keramika, no. 2 (2022): 3–7. http://dx.doi.org/10.14489/glc.2022.02.pp.003-007.

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The rise of polarization-controlled birefringence under a series of femtosecond laser pulses in the bulk of lithium silicate and lithium aluminosilicate glasstentatively attributed to the formation of nanogratings is demonstrated. The dependences of the retardance of the light passing through the modified regions on the parameter of laser radiation and the chemical composition of the glass are determined. It is shown that an increase of Al2O3 content at the expense of alkali content in glass composition leads to an increase in the minimum number of pulses for the formation of a birefringent region, as well as an increase in the retardance.

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McKinnon, M. M. "Birefringence as a Mechanism for the Broadening and Depolarization of Pulsar Average Profiles." International Astronomical Union Colloquium 160 (1996): 253–56. http://dx.doi.org/10.1017/s0252921100041634.

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Shortly after orthogonal modes of polarization were observed in pulsar radio emission (Manchester et al. 1975), a series of theoretical papers (Cocke & Pacholczyk 1976, Melrose & Stoneham 1977, Melrose 1979) were quick to point out that these abrupt, 90 degree transitions in polarization position angle could be explained by a propagation effect. More specifically, the plasma above pulsar polar caps may be birefringent. The orthogonal modes separate because they have different indices of refraction. So, as Allen & Melrose (1982) point out, the plasma is somewhat analogous to a terrestrial birefringent crystal, at least in the way it affects the ray paths of the modes. With very sensitive observations of individual pulse polarization, Stinebring et al. (1984) concluded that orthogonal modes are superposed, meaning they occur simultaneously. This observation is consistent with the birefringence hypothesis. Stinebring et al. also suggested that pulsars depolarize at high radio frequency via the superposed modes. Barnard & Arons (1986) expanded on the earlier theoretical work, and proposed that, in addition to orthogonal modes, birefringence could account for the broadening of pulsar average profiles at low radio frequency and their depolarization at high frequency. The purpose of this paper is to further investigate the suggestions of Stinebring et al. and Barnard & Arons.

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Journal articles on the topic 'Birefringence'

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