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A new polarization–interference biomedical diagnostic three-dimensional (3D) Jones-matrix technology with digital Fourier reconstruction of layered maps of optical anisotropy (thesiograms) of dehydrated films (facies) of biological fluids of human organs is presented and experimentally tested. An original model of layered phase scanning of polycrystalline architectonics of supramolecular networks of biological fluid facies is proposed for the purpose of theoretical justification and prognostic use of the obtained results. On its basis, algorithms of Jones-matrix reconstruction of thesiograms of birefringence and dichroism of facies of synovial fluid, bile and blood are found. As a result, layered thesiograms of linear and circular birefringence and dichroism of facies with different spatial–angular architectonics of supramolecular networks are experimentally obtained for the first time. Within the framework of statistical analysis of experimental data, new objective markers (asymmetry and excess of optical anisotropy parameter distributions) for diagnostics of pathological changes in the optical anisotropy of biological fluid facies were defined and clinically tested. As a result, an excellent level of balanced accuracy of the developed polarization–interference Jones-matrix method of layer-by-layer reconstruction of thesiograms of polycrystalline supramolecular networks in differential diagnostics of bile facies (cholelithiasis), synovial fluid (reactive synovitis–septic arthritis) and whole blood (follicular adenoma–papillary thyroid cancer) was achieved. [ABSTRACT FROM AUTHOR]

Optical vortices have the tremendous potential to increase data capacity by leveraging the extra degree of freedom of orbital angular momentum. On the other hand, anisotropic 2D materials are promising building blocks for future integrated polarization‐sensitive photonic and optoelectronic devices. Here, highly anisotropic third‐harmonic optical vortex beam generation is demonstrated with fork holograms patterned on ultrathin 2D germanium arsenide flakes. It is shown that the anisotropic nonlinear vortex beam generation can be achieved independent of the fork grating orientation with respect to the crystallographic orientation. Furthermore, 2D fork hologram is designed to generate multiple optical vortices having different topological charges with strong anisotropic responses. These results pave the way toward the advancement of 2D material‐based anisotropic nonlinear optical devices for future applications in photonic integrated circuits, optical communication, and optical information processing. [ABSTRACT FROM AUTHOR]

As an exceptional optical gene, the [PO4] tetrahedron is indispensable in the field of optical crystals due to its gain in the band gap of solid materials. However, the high symmetry of [PO4] tetrahedron hinders the achievement of large optical anisotropy in the lattice for phosphate crystal forms. In this work, the heteroleptic tetrahedra strategy, which involves replacing some of the oxygen atoms on regular oxy‐tetrahedra, is proven to be a feasible approach for preserving the wide transmission of the original [PO4] tetrahedra and improving the polarizability anisotropy. Based on this, eight methylphosphates are designed and synthesized for the phosphate system by substituting a [CH3] group for the O atom on the [PO4] tetrahedra. Theoretically, as compared to [PO4] units, [CH3PO3] and [CH3PO3H] units can improve the polarizability anisotropy, particularly [CH3PO3H] units, which have the potential to be birefringence‐active. The strong birefringence (exp. 0.108@546.1 nm) and short deep‐UV cutoff edge (195 nm) of nonmetallic methylphosphates [C(NH2)3][CH3PO3H] in the series suggest that it may be a possible short‐wave UV birefringent crystal. In addition to providing new birefringence‐active units for optical material design, this study validates the viability of modifying tetrahedra to improve inherent short board of nearly rigid [PO4] tetrahedra in phosphate family. [ABSTRACT FROM AUTHOR]

Black phosphorus (BP) is a layered orthorhombic crystal with uniquely arranged atoms forming a crumpled honeycomb lattice. This special atomic arrangement gives BP unique optical anisotropy, which is expected to be widely used in polarized optics. However, conventional image analysis used to study its anisotropy is complex and inefficient. This paper proposed a machine-learning-based approach to conveniently identify black phosphorus's optical anisotropy features. Red–green–blue (RGB) values were extracted from regions of interest (ROI) with a consistent thickness by the detection algorithm, and then the data were processed to obtain a sample eigenvalue data set. Variations in the RGB values of the optical image directly reflect changes in the ability of black phosphorus to reflect polarized light. RGB was converted to grayscale, and it was found that they both change periodically with the rotation angle. Subsequently, redundant data were eliminated by meticulously assessing feature importance, reducing generalization errors. The performance of the models was evaluated in terms of accuracy, recall, F1_Score, and area under the receiver operating characteristic curve (AUC-ROC), all of which were found to be consistently above 0.9. Machine learning algorithmic models can accurately classify BP images with different rotation angles to identify the optical anisotropy features of BP. Machine learning algorithms can automatically learn from the data and improve the algorithms, bolstering problem-solving efficiency and precision. This minimizes human and material resource waste from experimental errors, fostering interdisciplinary synergy between materials science and artificial intelligence. [ABSTRACT FROM AUTHOR]

The principles and effectiveness of the method of laser polarization interferometry of dehydrated blood films (facies) for the differential diagnosis of thyroid pathology have been studied. For this purpose, a theoretical description of the processes of formation and layer-by-layer phase scanning of the polarization structure of speckle fields in the blood facies of donors and patients with nodular goiter, autoimmune thyroiditis, and papillary cancer has been developed for the first time. A statistical analysis of holographically reconstructed maps of polarization ellipticity of the singly scattered component of the speckle field was conducted. Based on this analysis, the most sensitive markers for the diagnosis and differentiation of thyroid pathology were identified. Excellent diagnostic accuracy (91%–93%) and very good differentiation accuracy (86%–89%) were achieved for nodular goiter, autoimmune thyroiditis, and papillary cancer. [ABSTRACT FROM AUTHOR]

Nanostructured metamaterials can offer optical properties beyond what is achievable in conventional media, such as negative refraction or sub‐wavelength imaging. Due to their structural anisotropy, the class of high aspect ratio metamaterials is of interest for the possibility of achieving hyperbolic optical properties, i.e., both metallic and dielectric behavior based on the excitation direction. Although investigated numerically, the fabrication of tailor‐made metamaterials is complex or often beyond the reach of current technology. For wire metamaterials composed of aligned metallic nanowires in a dielectric matrix, since the free carrier concentration in metals is fixed, light‐matter interaction cannot be adjusted after fabrication. Here, metamaterials based on plasmonic ITO nanotubes with controllable hyperbolic response are introduced. The synthesis is achieved by a template‐based liquid‐phase technique. The tuning mechanism is based on controlling the carrier density in ITO via oxygen vacancy concentration. The process is reversible, the photonic features are activated by creating oxygen vacancies and can be switched off by filling them up again. Further, it is shown that the carrier concentration can also be controlled via a static electric field. Optical simulations support the experimental findings and highlight the parameters that determine the optical response of the metamaterial. [ABSTRACT FROM AUTHOR]

Polarimetric infrared (IR) detection bolsters IR thermography by leveraging the polarization of light. Optical anisotropy, i.e., birefringence and dichroism, can be leveraged to achieve polarimetric detection. Recently, giant optical anisotropy is discovered in quasi‐1D narrow‐bandgap hexagonal perovskite sulfides, A1+xTiS3, specifically BaTiS3 and Sr9/8TiS3. In these materials, the critical role of atomic‐scale structure modulations in the unconventional electrical, optical, and thermal properties raises the broader question of the nature of other materials that belong to this family. To address this issue, for the first time, high‐quality single crystals of a largely unexplored member of the A1+xTiX3 (X = S, Se) family, BaTiSe3 are synthesized. Single‐crystal X‐ray diffraction determined the room‐temperature structure with the P31c space group, which is a superstructure of the earlier reported P63/mmc structure. The crystal structure of BaTiSe3 features antiparallel c‐axis displacements similar to but of lower symmetry than BaTiS3, verified by the polarization dependent Raman spectroscopy. Fourier transform infrared (FTIR) spectroscopy is used to characterize the optical anisotropy of BaTiSe3, whose refractive index along the ordinary (E ⊥ c) and extraordinary (E ‖ c) optical axes is quantitatively determined by combining ellipsometry studies with FTIR. With a giant birefringence Δn ∼ 0.9, BaTiSe3 emerges as a new candidate for miniaturized birefringent optics for mid‐wave infrared to long‐wave infrared imaging. [ABSTRACT FROM AUTHOR]

Polarimetric infrared (IR) detection bolsters IR thermography by leveraging the polarization of light. Optical anisotropy, i.e., birefringence and dichroism, can be leveraged to achieve polarimetric detection. Recently, giant optical anisotropy is discovered in quasi‐1D narrow‐bandgap hexagonal perovskite sulfides, A1+xTiS3, specifically BaTiS3 and Sr9/8TiS3. In these materials, the critical role of atomic‐scale structure modulations in the unconventional electrical, optical, and thermal properties raises the broader question of the nature of other materials that belong to this family. To address this issue, for the first time, high‐quality single crystals of a largely unexplored member of the A1+xTiX3 (X = S, Se) family, BaTiSe3 are synthesized. Single‐crystal X‐ray diffraction determined the room‐temperature structure with the P31c space group, which is a superstructure of the earlier reported P63/mmc structure. The crystal structure of BaTiSe3 features antiparallel c‐axis displacements similar to but of lower symmetry than BaTiS3, verified by the polarization dependent Raman spectroscopy. Fourier transform infrared (FTIR) spectroscopy is used to characterize the optical anisotropy of BaTiSe3, whose refractive index along the ordinary (E ⊥ c) and extraordinary (E ‖ c) optical axes is quantitatively determined by combining ellipsometry studies with FTIR. With a giant birefringence Δn ∼ 0.9, BaTiSe3 emerges as a new candidate for miniaturized birefringent optics for mid‐wave infrared to long‐wave infrared imaging. [ABSTRACT FROM AUTHOR]

Polarized light is critical for a wide range of applications in modern optics. However, its generation and modulation typically require additional optical comments, which hinders device compactness. Herein, an air‐stable Tin(IV)‐based hybrid metal halide, (C10H9N2O)2SnCl6, composed of [C10H9N2O]+ cations and isolated [SnCl6]2− octahedra is reported. Notably, (C10H9N2O)2SnCl6 exhibits a robust birefringence of 0.50@550 nm that is evidently larger than those of commercially used crystals, which enables efficient modulation of polarized light. Moreover, it possesses a broad polarized blue emission in the range of 374–600 nm with a peak at 426 nm. Theoretical and structural studies reveal that the high optical anisotropy for large birefringence and directly polarized emission of (C10H9N2O)2SnCl6 is ascribed to the cooperative effect of distortion of [SnCl6]2− and high π‐conjugation of [C10H9N2O]+ in parallel arrangement. This work may provide new thoughts on designing and realizing the miniaturization of polarization‐resolved optoelectronic devices. [ABSTRACT FROM AUTHOR]

The understanding of the optical characteristics and the influence of thermally induced crystallization is vital to evaluate newly synthesized organic semiconductors for their potential applications. Variable‐angle spectroscopic ellipsometry (VASE) is employed to determine the complex dielectric function of two recently developed discrete oligomers based on naphthalene diimide (NDI) and bithiophene (T2), applying an anisotropic optical model. It is shown that the as‐cast films are optically near‐isotropic, while the annealed films exhibit pronounced anisotropies with respect to the orientation of the π−π* transition. Differences between the two distinct molecules are observed and discussed. The degree of optical anisotropy is quantified using the average molecular orientation angle φ, associated with the orientation of the π−π* transition dipole, and the related orientation order parameter S. The molecules are shown to form crystallites of several microns in size upon annealing. Imaging ellipsometry is thus additionally employed to study their optical anisotropy on a microscopic scale, and the agreement with results from macroscopic measurements is evaluated. [ABSTRACT FROM AUTHOR]

Optical anisotropic (e.g., birefringent) crystals can manipulate the polarization of light and thus are widely applied in modern optical fields. Common birefringent crystals are almost exclusively limited to inorganic oxides with small birefringence. Here, a new 1D hybrid halide perovskite PZPbCl3 (PZ = phenazine) is reported, which consists of perfectly parallel Pb–Cl chains and PZ cations. Remarkably, polarized optical observations show that even a PZPbCl3 crystal with micrometer thickness can modulate the polarized light efficiently. Furthermore, PZPbCl3 exhibits exceptional birefringence up to 0.65@546 nm, which is significantly larger than that of commercial oxide crystals. According to first‐principles calculations and polarizability anisotropy analyses, it is found that this birefringence is mainly ascribed to the linear polymerization of π‐conjugated rings in PZ cations. Due to the rich physical properties and structural diversity of hybrid perovskites, it is believed that the introduction of excellent birefringence into the hybrid perovskites will bring unprecedented opportunities to the future explorations of polarization‐dependent functional materials. [ABSTRACT FROM AUTHOR]

The lattice geometry of natural materials and the structural geometry of artificial materials are crucial factors determining their physical properties. Most materials have predetermined geometries that lead to fixed physical characteristics. Here, the demonstration of a carbon nanotube network serves as an example of a system with controllable orientation achieving on‐demand optical properties. Such a network allows programming their optical response depending on the orientation of the constituent carbon nanotubes and leads to the switching of its dielectric tensor from isotropic to anisotropic. Furthermore, it also allows for the achievement of wavelength‐dispersion for their principal optical axes – a recently discovered phenomenon in van der Waals triclinic crystals. The results originate from two unique carbon nanotubes features: uniaxial anisotropy from the well‐defined cylindrical geometry and the intersection interaction among individual carbon nanotubes. The findings demonstrate that shaping the relative orientations of carbon nanotubes or other quasi‐one‐dimensional materials of cylindrical symmetry within a network paves the way to a universal method for the creation of systems with desired optical properties. [ABSTRACT FROM AUTHOR]

The LD conversion offers great potential in providing an additional degree of freedom that may be beneficial to novel polarization‐wavelength‐selective detectors and optical switching. However, conventional crystals with optical anisotropy typically show unidirectional LD over a broad wavelength range and the materials with LD conversion behavior remain scarce. Here, by combining angle‐resolved polarized optical absorption measurements and theoretical calculations, this study demonstrates that quasi‐1D Weyl semimetal (TaSe4)2I single crystal shows unique LD conversion phenomenon at the wavelength of 1064 nm. Meanwhile, (TaSe4)2I persists giant linear optical anisotropy due to the intrinsic feature of 1D [TaSe4] chains along the c‐axis. Additionally, the (TaSe4)2I nanoribbon exhibits anisotropic second harmonic generation (SHG). These results hold significant importance to facilitate the development of topological photonics and novel photonic devices applications based on topological semimetals. [ABSTRACT FROM AUTHOR]

Porous semiconductors have garnered significant attention owing to their distinctive physical and chemical properties. In this study, optical anisotropy is presented in porous germanium (PGe) on a Si (001) substrate. Both n‐ and p‐type PGe, achieved through bipolar electrochemical etching, exhibit optical anisotropy along the Ge <001> direction, as determined by spectroscopic ellipsometry. Birefringence and depolarization factors are controllable by adjusting the etching parameters and doping concentration of the epitaxial Ge layer. The gradient porosity and pore distribution in PGe can be well captured by the optical models. The findings of optical anisotropy in PGe‐on‐Si hold promise for applications in optical elements or sensors for gas or biomolecules. [ABSTRACT FROM AUTHOR]

Tetrahedral oxygenated groups with large highest occupied molecular orbital‐lowest unoccupied molecular orbital (H gaps such as [SO4] are beneficial for deep ultraviolet (DUV) transmission but usually make against generating sufficient birefringence due to the small polarizability anisotropy. Thus, it is extremely difficult to obtain DUV transmission and large birefringence simultaneously in the search for DUV birefringent materials in sulfates. Herein, two new ammonium‐rare earth metal sulfates, NH4Y(SO4)2·H2O and NH4YSO4F2, with DUV transmission are presented. Meanwhile, both exhibit greatly elevated birefringence through the involvement of NH4+ units, compared to Y2(SO4)3·8H2O. Their optical properties are further investigated by theoretical calculations, and the effect of the introduction of NH4+ into yttrium sulfate on optimizing the structures and properties is discussed. This work may provide a new perspective for further exploration of DUV birefringent materials in tetrahedral oxygenated group sulfates. [ABSTRACT FROM AUTHOR]

In this study, the structural, optical, and elastic properties of tetragonal MgTa2O6 and orthorhombic MgNb2O6 were determined using the Wien2k and ABINIT computational programs with the aid of density functional theory. The results imply that both compounds are classified as wide band gap semiconductor with 4.143 eV (for MgTa2O6) and 3.653 eV (for MgNb2O6) with PBEsol-GGA + TB-mBJ approximation. The findings of bulk modulus, shear modulus, Young modulus, Poisson's ratio, and anisotropy factors were determined and discussed in detail. The ductile behavior and the mechanism of structural stability were also explained. [ABSTRACT FROM AUTHOR]

Multi-phase vertically aligned nanocomposite (MP-VAN) thin films represent a promising avenue for achieving complex multifunctionality, exploring novel interfacial phenomena, and enabling complex metamaterial designs and exploration. In this study, a novel self-assembled all-oxides three-phase VAN system was conceptualized and fabricated utilizing pulsed laser deposition (PLD) with a single composite target. Detailed microstructural analysis reveals the presence of three distinct phases: LiNbO3, CeO2−x, and LiNbCe1−xOy within the MP-VAN films. Subsequently, ferroelectric, dielectric, optical anisotropy, and magnetic properties were systematically investigated to showcase the multifunctionality inherent in these films. This work presents a pioneering approach to designing and realizing MP-VAN systems, and opens up opportunities for tailoring the complex three-dimensional (3D) physical properties and property coupling of VAN films towards diverse device applications. [ABSTRACT FROM AUTHOR]

Materials with large birefringence (Δn, where n is the refractive index) are sought after for polarization control (e.g., in wave plates, polarizing beam splitters, etc.), nonlinear optics, micromanipulation, and as a platform for unconventional light-matter coupling, such as hyperbolic phonon polaritons. Layered 2D materials can feature some of the largest optical anisotropy; however, their use in most optical systems is limited because their optical axis is out of the plane of the layers and the layers are weakly attached. This work demonstrates that a bulk crystal with subtle periodic modulations in its structure-Sr9/8 TiS3 -is transparent and positive-uniaxial, with extraordinary index ne = 4.5 and ordinary index no = 2.4 in the mid- to far-infrared. The excess Sr, compared to stoichiometric SrTiS3 , results in the formation of TiS6 trigonal-prismatic units that break the chains of face-sharing TiS6 octahedra in SrTiS3 into periodic blocks of five TiS6 octahedral units. The additional electrons introduced by the excess Sr form highly oriented electron clouds, which selectively boost the extraordinary index ne and result in record birefringence (Δn > 2.1 with low loss). The connection between subtle structural modulations and large changes in refractive index suggests new categories of anisotropic materials and also tunable optical materials with large refractive-index modulation.

The combination of rigid (AlO 6) and deformable (MoO 6 and TeO 3) groups leads to a robust birefringent crystal (Al 2 Te 2 MoO 10) for compact optical polarization components which could efficiently divide one incident light into two polarized beams. [Display omitted] There is a pressing demand for the development of novel birefringent crystals tailored for compact optical components, especially for crystals exhibiting large birefringence across a range of temperatures. This has commonly been achieved by introducing various deformable groups with high polarizability anisotropy. In this study, we combined both rigid and deformable groups to synthesise a new birefringent crystal, Al 2 Te 2 MoO 10 , which demonstrates an exceptional birefringence value of 0.29@550 nm at room temperature. Not only is this higher birefringence than that of commercial crystals, but Al 2 Te 2 MoO 10 exhibits excellent birefringence stability over a wide temperature range, from 123 to 503 K. In addition, the first-principles theory calculations and structural analyses suggest that although the rigid AlO 6 groups do not make much contribution to the prominent birefringence, they nonetheless played a role in maintaining the structural anisotropy at elevated temperatures. Based on these findings, this paper proposes a novel structural design strategy to complement conventional approaches for developing optimal birefringent crystals under various environmental conditions. [ABSTRACT FROM AUTHOR]

The novel ternary 2D material Bi2O2Se exhibits numerous unique properties in the optical discipline due to its distinctive structure, rendering it of significant research importance and application potential in the domains of new‐generation microelectronics, optoelectronic sensors, and multidimensional optical recognition. However, the optical anisotropy and multidimensional angular resolution of Bi2O2Se have yet to be investigated under the condition of 3D spatial variation of incidence angle. Herein, the spatial optical sensing of the few‐layer Bi2O2Se is investigated under 3D spatially varying incidence conditions using a combination of polarized Raman spectroscopy and multidimensional angle‐resolved spectroscopy. By manipulating the incident angle conditions and adjusting the sample placement angle, a comprehensive optical characterization of materials from diverse spatial orientations is conducted. It is observed that few‐layer Bi2O2Se exhibits a systematically transformed multidimensional spatial photoresponse within visible and near‐infrared wavelengths. This demonstrates the capability of Bi2O2Se as photosensitive semiconductors for 3D stereo optical detection. Furthermore, finite difference time domain simulations reveal that the spatial optical anisotropy of few‐layer Bi2O2Se can be manifested under 3D variable‐angle incidence conditions. The work serves as a crucial guide for the future of Bi2O2Se in anisotropic integrated optics applications, based on polarization‐based chiral recognition. [ABSTRACT FROM AUTHOR]

Borates have garnered a lot of attention in the realm of solid‐state chemistry due to their remarkable characteristics, in which the synthesis of borates with isolated [BO3] by adding rare‐earth elements is one of the main areas of structural design study. Five new mixed‐metal Y‐based rare‐earth borates, Ba2ZnY2(BO3)4, KNa2Y(BO3)2, Li2CsY4(BO3)5, LiRb2Y(BO3)2, and RbCaY(BO3)2, have been discovered using the high‐temperature solution approach. Isolated [BO3] clusters arranged in various configurations comprise their entire anionic framework, allowing for optical anisotropy tuning between 0.024 and 0.081 under 1064 nm. In this study, we characterize the relative placements of their [BO3] groups and examine how their structure affects their characteristics. The origin of their considerable optical anisotropy has been proven theoretically. This study unequivocally demonstrates that even a slight alteration to borates′ anionic structure can result in a significant improvement in performance. [ABSTRACT FROM AUTHOR]

Chirality is one of the most mysterious symmetry transformations. Very readily broken in biological systems, it is practically absent in naturally occurring inorganic materials and is very challenging to create artificially. Chiral optical wavefronts are often used for the identification, control, and discrimination of left‐ and right‐handed biological and other molecules. Thus, it is crucially important to create materials capable of chiral interaction with light, which would allow one to assign arbitrary chiral properties to a light field. This study utilizes van der Waals technology to assemble helical homostructures with chiral properties (e.g., circular dichroism). Because of the large range of van der Waals materials available, such helical homostructures can be assigned with very flexible optical properties. The approach is demonstrated by creating helical homostructures based on multilayer As2S3${\rm As}_2{\rm S}_3$ (arsenic trisulfide), which offers the most pronounced chiral properties even in thin structures due to its strong biaxial optically anisotropy. The work showcases that the chirality of an electromagnetic system may emerge at an intermediate level between the molecular and the mesoscopic one due to the tailored arrangement of non‐chiral layers of van der Waals crystals and without additional patterning. [ABSTRACT FROM AUTHOR]

The elastic, vibrational, and electro-optical properties of WSe2 using the first-principles approach have been explored in this study. The lattice parameters of WSe2 are consistent with the available results. The structural stability of WSe2 has been proven by satisfying the stability conditions and from the phonon dispersion spectra. According to the elastic constants and moduli, WSe2 is a material with a high level of machinability, rather soft, mechanically and elastically anisotropic, and brittle in nature. The relatively lower values of the thermodynamic parameters suggest that WSe2 could be an excellent option as a thermal barrier coating (TBC) material. The overlap of the acoustic and optical modes of phonons in the lower frequency region is responsible for the enhancement of the anharmonicity of the crystal and hence reduces the thermal conductivity. WSe2 is an indirect band gap material with band gap values 0.88 (LDA) and 1.329 eV (sX-LDA) with small values of carrier effective mass. Therefore, WSe2 could be a potential candidate for electronic device applications. The optical investigation revealed that the material has a high refractive index, dielectric constant, and absorption coefficient, and considerable optical anisotropy. According to the reflectivity spectra, WSe2 could be employed as an anti-reflection coating material. By examining the optical properties, it can be noted that WSe2 is widely used to develop wave-guides, photonic devices, photovoltaic cells, and other optoelectronic devices. [ABSTRACT FROM AUTHOR]

Perfect light transmission into a dielectric at the Brewster angle is one of the simplest effects of macroscopic electromagnetism. The common wisdom states that absorption in the dielectric violates Brewster angle and leads to a non‐vanishing reflection. Yet, incorporating anisotropy may recover perfect transmission of p‐polarized light into the absorbing medium. Unlike the ordinary "lossless" Brewster angle, perfect transmission in this case is accompanied by phase singularities of the reflection amplitude. In this paper, phase singularities and the associated topological charges are theoretically examined as emerging in the wavelength‐incidence angle space upon perfect transmission into absorbing uniaxial dielectrics. The analytical criterion of perfect light transmission into an anisotropic medium is derived, phase singularities are demontrated in these scenarios, and their dynamics are studied as a function of material parameters. Finally, by lowering the symmetry of the problem, this phenomenon is translated into a different parameter space of wave vector components, and illustrate the feasibility of this phenomenon with available optically anisotropic materials. The results may become valuable for the development of novel analog computing schemes and holography approaches. [ABSTRACT FROM AUTHOR]

Perfect absorbers, widely utilized in solar energy‐harvesting devices, optical communications, sensors, displays, and filters, achieve 100% light absorption. However, perfect absorbers employing micro/nanostructures encounter challenges such as high cost and complexity in simulation and fabrication. Here, novel wavelength‐linearly‐dependent and polarization‐sensitive perfect absorbers utilizing optically anisotropic germanium selenide (GeSe) are proposed. A simple and cost‐effective GeSe‐SiO2‐Si multilayered optical thin film is constructed and optimized to achieve destructive interference, leading to perfect absorption. The operating wavelength can be linearly tuned from 900 nm to 1300 nm by adjusting the GeSe thickness from 125 nm to 200 nm. Leveraging the significant optical anisotropy, the polarization angle is introduced as an additional parameter to dynamically and finely control the operating wavelength, enabling the creation of polarization‐sensitive perfect absorbers. Experimental results validate the feasibility of fabricating and dynamically modulating the proposed wavelength‐linearly‐dependent and polarization‐sensitive perfect absorbers. This study introduces a novel approach for designing and fabricating reconfigurable perfect absorbers utilizing low‐symmetry materials, facilitating mass production and on‐chip integrated systems. [ABSTRACT FROM AUTHOR]

A solution to the direct ellipsometry problem is presented for a single-layer model of an isotropic substrate–anisotropic film in the case of the orientation of the film optical axis in the plane of incidence. Analytical expressions for calculating the ellipsometric parameters of such a structure are obtained. A simple numerical algorithm is proposed for determining the ordinary () and extraordinary () refractive indices of a bulk crystal under various measurement conditions. The inverse problem of determining , , and the film thickness when changing the azimuth of the optical axis is considered. The correlation of the required parameters for such a problem is discussed. [ABSTRACT FROM AUTHOR]

The principles and effectiveness of the method of laser polarization interferometry of dehydrated blood films (facies) for the differential diagnosis of thyroid pathology have been studied. For this purpose, a theoretical description of the processes of formation and layer-by-layer phase scanning of the polarization structure of speckle fields in the blood facies of donors and patients with nodular goiter, autoimmune thyroiditis, and papillary cancer has been developed for the first time. A statistical analysis of holographically reconstructed maps of polarization ellipticity of the singly scattered component of the speckle field was conducted. Based on this analysis, the most sensitive markers for the diagnosis and differentiation of thyroid pathology were identified. Excellent diagnostic accuracy (91%–93%) and very good differentiation accuracy (86%–89%) were achieved for nodular goiter, autoimmune thyroiditis, and papillary cancer.

Combining π‐conjugated and non‐π‐conjugated groups is an important strategy for synthesizing new nonlinear optical (NLO) crystals. However, the second harmonic generation (SHG) response and optical anisotropy can be limited by improper spatial alignment of these functional groups in the crystal structure. In this work, it is revealed that non‐π‐conjugated [NH2SO3] group acts as both hydrogen bond donor and acceptor, effectively regulating the 2D planar structure formed by π‐conjugated [C4N3H6] groups. The resulting organic–inorganic hybrid crystal C4N3H6SO3NH2 exhibits a strong SHG response (2.5 × KDP), large optical anisotropy (0.233@546 nm), and blue‐violet and green fluorescence near 360 and 520 nm, respectively. This work expands the methodology for creating new NLO crystals through organic–inorganic hybridization, while also showcasing the potential of C4N3H6SO3NH2 as a multifunctional optical material. [ABSTRACT FROM AUTHOR]

Significance: The interference-holographic method of phase scanning of fields of scattered laser radiation is proposed. The effectiveness of this method for the selection of variously dispersed components is demonstrated. This method made it possible to obtain polarization maps of biological tissues at a high level of depolarized background. The scale-selective analysis of such maps was used to determine necrotic changes in the optically anisotropic architectonics of biological tissues. Objective: Development and experimental approbation of layered phase polarimetry of repeatedly scattered fields in diffuse layers of biological tissues. Application of scale-selective processing of the found coordinate distributions of polarization states in various phase sections of object fields. Determination of criteria (markers) for histological differential diagnosis of the causes of necrotic changes in optical anisotropy of biological tissues. Approach: We used a synthesis of three instrumental and analytical methods. Polarization-interference registration of laser radiation scattered by a sample of biological tissue. Digital holographic reconstruction and layered phase scanning of distributions of complex amplitudes of the object field. Analytical determination of polarization maps of various phase cross-sections of repeatedly scattered radiation. Application of wavelet analysis of the distributions of polarization states in the phase plane of a single scattered component of an object field. Determination of criteria (markers) for differential diagnosis of necrotic changes in biological tissues with different morphological structure. Two cases are considered. The first case is the myocardium of those who died as a result of coronary heart disease and acute coronary insufficiency. The second case is lung tissue samples of deceased with bronchial asthma and fibrosis. Results: A method of polarization-interference mapping of diffuse object fields of biological tissues has been developed and experimentally implemented. With the help of digital holographic reconstruction of the distributions of complex amplitudes, polarization maps in various phase sections of a diffuse object field are found. The wavelet analysis of azimuth and ellipticity distributions of polarization in the phase plane of a single scattered component of laser radiation is used. Scenarios for changing the amplitude of the wavelet coefficients for different scales of the scanning salt-like MHAT function are determined. Statistical moments of the first to fourth orders are determined for the distributions of the amplitudes of the wavelet coefficients of the azimuth maps and the ellipticity of polarization. As a result, diagnostic markers of necrotic changes in the myocardium and lung tissue were determined. The statistical criteria found are the basis for determining the accuracy of their differential diagnosis of various necrotic states of biological tissues. Conclusions: Necrotic changes caused by "coronary artery disease--acute coronary insufficiency" and "asthma--pulmonary fibrosis" were demonstrated by the method of wavelet differentiation with polarization interference with excellent accuracy. [ABSTRACT FROM AUTHOR]

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Although the investigation of the propagation of electromagnetic waves in crystals dates back to the 19th century, the presence of singular optic axes in optically anisotropic materials has not been fully explored until now. Along such an axis, either a left or a right circular polarized wave can propagate without changing its polarization state. More generally, these singular optic axes belong to exceptional points (EPs) in the momentum space and correspond to a simultaneous degeneration of the eigenmodes and their propagation properties. Herein, a comprehensive discussion on EPs in optically anisotropic materials, their occurrence, and properties as well as the properties of the electromagnetic waves propagating along such EPs is presented. The presence of such EPs, their spatial and spectral distribution in bulk, and semi‐infinite and finite crystals are discussed. It is shown that the presence of interfaces has a strong impact on the presence of the EPs and their spatial distribution. At an EP, the propagation of an arbitrarily polarized wave cannot be described by a superposition of two eigenmodes, as typically described in textbooks. This leads to singularities if the reflection and transmission coefficients have to be calculated. Here, two approaches are presented to overcome these limitations. [ABSTRACT FROM AUTHOR]

Large birefringence is a crucial but hard‐to‐achieve optical parameter that is a necessity for birefringent crystals in practical applications involving modulation of the polarization of light in modern opto‐electronic areas. Herein, an oxyanion polymerization strategy that involves the combination of two different types of second‐order Jahn–Teller distorted units is employed to realize giant anisotropy in a covalent molybdenum tellurite. Mo(H2O)Te2O7 (MTO) exhibits a record birefringence value for an inorganic UV‐transparent oxide crystalline material of 0.528 @ 546 nm, which is also significantly larger than those of all commercial birefringent crystals. MTO has a UV absorption edge of 366 nm and displays a strong powder second‐harmonic generation response of 5.4 times that of KH2PO4. The dominant roles of the condensed polytellurite oxyanions [Te8O20]8− in combination with the [MoO6]6− polyhedra in achieving the giant birefringence in MTO are clarified by structural analysis and first‐principles calculations. The results suggest that polymerization of polarizability‐anisotropic oxyanions may unlock the promise of birefringent crystals with exceptional birefringence. [ABSTRACT FROM AUTHOR]

Self‐trapped exciton (STE) induced broad‐band emission (BE) has sparked considerable interest due to its potential applications in white‐light emitters and optoelectronics. This phenomenon is widely observed in organic–inorganic hybrid perovskites with soft lattice structures, and its physical origin is still under debate. Herein, strong sub‐bandgap STE emission with a large Stokes shift and a photoluminescence quantum yield of up to 9.2% in van der Waals (vdW) layered In4/3P2S6 is reported. Combining comprehensive optical characterizations and theoretical calculations, this concludes that defect‐assisted extrinsic STE is responsible for the BE. The excitonic state can be further localized by hydrostatic pressure, resulting in a threefold PL intensity enhancement. In addition, angle‐resolved polarized Raman demonstrates the anisotropic lattice dynamics in IPS, which may underpin the highly linear anisotropy of the STE emission. This work clarifies the defect, STE, and anisotropy coupling effect in vdW crystal, and provides innovative avenues to modulate the STE luminescence. [ABSTRACT FROM AUTHOR]

Self‐trapped exciton (STE) induced broad‐band emission (BE) has sparked considerable interest due to its potential applications in white‐light emitters and optoelectronics. This phenomenon is widely observed in organic–inorganic hybrid perovskites with soft lattice structures, and its physical origin is still under debate. Herein, strong sub‐bandgap STE emission with a large Stokes shift and a photoluminescence quantum yield of up to 9.2% in van der Waals (vdW) layered In4/3P2S6 is reported. Combining comprehensive optical characterizations and theoretical calculations, this concludes that defect‐assisted extrinsic STE is responsible for the BE. The excitonic state can be further localized by hydrostatic pressure, resulting in a threefold PL intensity enhancement. In addition, angle‐resolved polarized Raman demonstrates the anisotropic lattice dynamics in IPS, which may underpin the highly linear anisotropy of the STE emission. This work clarifies the defect, STE, and anisotropy coupling effect in vdW crystal, and provides innovative avenues to modulate the STE luminescence. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]