High Birefringence Research Articles

Dual Lone Pair Strategy for High Birefringence in Antimony(III)-Based Tellurite Sulfates with Short-Wave UV Transparency.

We present two novel antimony(III)-based tellurite sulfate crystals, Sb2(TeO3)(SO4)2-P1̅ (I) and Sb2(TeO3)(SO4)2-P21/c (II), synthesized using a dual lone pair strategy that incorporates Sb3+ and Te4+ ions into a sulfate framework. This approach significantly enhances the birefringence of these compounds, with values of 0.11 and 0.10 at 546 nm, respectively, surpassing those of many previously reported mixed alkali metal/alkaline earth metal sulfates and tellurites. Both compounds also exhibit excellent UV transparency with cutoff edges at 292 and 294 nm, making them promising candidates for short-wave UV optical applications. Structural and theoretical analyses reveal that the enhanced birefringence arises from the synergistic effects of the stereochemically active lone pairs of Sb3+ and Te4+, which contribute to the optical anisotropy. This work highlights the potential of dual SCALP elements in improving the optical properties of sulfate-based crystals and provides new insights into designing high-performance optical materials with tailored properties for advanced UV technologies.

Ferroelectric Nematic Liquid Crystals Showing High Birefringence.

High birefringence nematic liquid crystals are particularly demanded for adaptive optics applications in the infrared spectrum because it enable a thinner cell gap for achieving fast response time and improved diffraction efficiency. The emerging ferroelectric nematic liquid crystals have attracted widespread interest in soft matter due to their unique combination of ferroelectricity and fluidity. However, the birefringence, which is one of the most important optical parameters in electro-optic devices, is not large enough (<0.25) in most ferroelectric nematic materials. Here, a polar liquid crystal molecule library containing more than 60 molecules with a highly rigid and fluorinated nature is developed. The introduction of triple bonds constructs a long π-electron conjugated mesogen skeleton, significantly improving the birefringence of polar liquid crystal phases. The birefringence and dispersion properties are systematically studied, demonstrating a strong dependence on chemical structures and the type of polar phases. Furthermore, through multi-component mixing, polar liquid crystal mixtures with ultra-wide temperature range and excellent stability at or near room temperature are obtained. They possess much higher birefringence than the existing ferroelectric liquid crystal materials. The unique combination of high birefringence and fluidic ferroelectricity is expected to promote the application of polar liquid crystals in electro-optic technologies.

Hybrid hexa-octagonal photonic crystal fiber with excellent guiding properties for sensing and communication applications

Abstract A novel hybrid hexa-octagonal photonic crystal fiber (PCF) is designed by integrating a hexagonal arrangement of elliptical air holes in the core using soft glass and an octagonal lattice of circular air holes in the cladding. This study presents a comparative analysis of the fiber parameters, including confinement loss, non-linearity, effective area, birefringence, and chromatic dispersion, for two configurations: (i) hybrid hexa-octagonal PCF with a horizontal arrangement of air holes in the core, and (ii) hybrid hexa-octagonal PCF with a vertical arrangement of air holes in the core. Both configurations are examined by varying the pitch size, arrangement, and shape of air holes while maintaining identical design and operational features. Simulations are conducted using the full vector finite element method (FEM). Numerical results indicate that the confinement loss for vertically and horizontally arranged air holes is 1.098 × 10−5 dB km−1 and 1.0743 × 10−5 dB km−1, respectively. High birefringence values of 0.07366 and 0.00434, and chromatic dispersion values of −3404.665 ps nm−1 km and −3391.6705 ps nm−1 km, respectively, are obtained at an operating wavelength of 1.55 µm, making the fiber suitable for sensing and communication applications. The designed hexa-octagonal PCF has potential applications in the fiber optic sensing due to its assorted features.

Highly birefringent and low loss anti-resonant hollow-core fiber with stadium-shaped nested structure

Abstract We propose a stadium-shaped nested anti-resonant hollow-core fiber (SSAF), designed to enable high birefringence and low loss in the near-infrared bands. Numerical investigation and simulation for variations in parameters of stadium-shaped nested structure are conducted, and confinement loss (CL) is reduced by parameters optimization while birefringence of 10−4 is maintained. With optimized SSAF structure, the birefringence and CL are improved to 1.39 × 10−4 and 26.5 dB km−1 at 1.38 µm, 1.28 × 10−4 and 2.64 dB km−1 at 1.55 µm, respectively. Meanwhile, it exhibits favorable single-mode characteristics and achieves a high high-order mode extinction ratio of up to 103, and the superior bending resistance characteristics are validated. Our work offers valuable guidance for designing and optimizing highly birefringent SSAF anti-resonant fiber, and the proposed SSAF has great application potential in polarization-dependent transmission and interferometric fiber gyroscope.

Fast and large refractive index switching of optically isotropic liquid crystal films

ABSTRACT Polymer Dispersed Liquid Crystals (PDLCs) consist of low molecular weight liquid crystal (LC) droplets embedded in a polymer matrix. Nano-PDLCs are a special type of PDLCs where the LC droplet sizes are in the nanometre range. For normal incidence of light, the nano-PDLC has a voltage dependent, isotropic refractive index that could be used to make polarisation independent tunable lenses. Here, we report the effect of chiral dopant on haze, switching time and field-induced variation of the refractive index δn E of PDLC materials having a high birefringence ( Δn = 0.38 at 550 nm ) nematic liquid crystal dispersed in a polymer matrix. As an effect of the chiral dopant, δn decreases slightly from 0.05 to 0.037 at E = 10 V / μm , however the relaxation time and the haze decrease to a much larger extent from 2.5 ms to 0.3 m s, and from 50% to less than 10% at 550 nm, respectively. These improvements are due to the sub-micrometer helical pitch in the LC droplets that reduces the size of the LC droplets well below 1 µm, leading to nano-PDLC with sub-millisecond switching time and low haze.

Vinyl Ketones Containing Fluorene Skeletons for Acrylic Resins with High Refractive Index and Negative Birefringence

Vinyl Ketones Containing Fluorene Skeletons for Acrylic Resins with High Refractive Index and Negative Birefringence

Broadband high birefringence and single-polarization hollow-core anti-resonant fibers with an elliptical-like core

Due to the light-guiding mechanism of hollow-core anti-resonant fibers (HC-ARFs), the low overlap between core modes and anti-resonant layers poses a challenge in achieving high birefringence. To address this issue, we propose three high-birefringence HC-ARFs with an elliptical core and varying cladding compositions and conduct a detailed optimization and analysis for structure (c). Simulation results demonstrate that structure (a) and structure (b) provide high birefringence, broadband, and low-loss transmission properties. Specifically, structure (a) achieves a birefringence greater than 1.3×10−4 over a 680 nm wavelength range, and structure (b) achieves a birefringence greater than 1.6×10−4 over a 580 nm wavelength range, both maintaining fundamental mode (FM) loss below 1 dB/m. Structure (c) enhances birefringence by an order of magnitude and offers excellent single-polarization properties by introducing high-refractive-index material. At 1.55μm, structure (c) achieves a birefringence of 0.98×10−3, with a low FM loss for x-polarization of 0.01 dB/m and a polarization extinction ratio (PER) of 57450. Additionally, structure (c) exhibits low bend loss in the x-direction, with only 0.06 dB/m for a bend radius of 6 cm.

Design and error analysis of simple terahertz high birefringence microstructured fiber

Abstract High birefringence fibers are significant in the terahertz technology field, serving as waveguides for terahertz transmission. They are applicable in various fields such as communication, imaging. Integrating metal microstructures into polymer microstructured optical fibers can effectively modulate the transmission characteristics of the fiber, enhancing birefringence and reducing loss, thereby achieving better performance compared to traditional single-material fibers. This paper presents a structurally simple terahertz high birefringence microstructured fiber, where the introduction of gold microstructures enhances the birefringence of fiber, with a maximum birefringence of up to 1.089 × 10−2. We also discuss several manufacturing errors that may occur during the fiber fabrication process. The results indicate that the designed fiber exhibits significant manufacturing tolerance. Variations in the thickness and angle of the gold microstructures, as well as the angular offset of the elliptical cladding wall, peak-to-valley errors, and changes in the aspect ratio of the elliptical tube, have relatively minor effects on the overall transmission performance. The research findings provide insights for designing subsequent high birefringence terahertz fibers, thereby propelling advancements in this field. They offer a theoretical basis for the preparation of related microstructured fiber structures and provide valuable understanding for optimizing fiber manufacturing processes.

Graph neural network guided design of novel deep-ultraviolet optical materials with high birefringence

Graph neural network guided design of novel deep-ultraviolet optical materials with high birefringence

Design of simple circular photonic crystal fiber having ultra-large negative dispersion and high birefringence for dispersion compensation

Design of simple circular photonic crystal fiber having ultra-large negative dispersion and high birefringence for dispersion compensation

Broadband and tunable fiber polarizer based on a graphene photonic crystal fiber.

The recent flourishing development of two-dimensional (2D) graphene has sparked considerable interest and extensive research on graphene-based optical fiber polarizers. However, studies on graphene-optical fiber polarizers focused on the structure with graphene films attached to side-polished fibers, which face challenges such as low birefringence of 10-6, low polarization extinction ratio (PER), and narrow polarizing window of tens of nanometers. Here, a fiber polarizer based on a graphene-photonic crystal fiber (Gr-PCF) is proposed firstly, which exhibits high birefringence of ∼2.5 × 10-3, high PER of ∼111 dB/mm, broad polarizing window of >400 nm, and tunable polarization states. Graphene or graphene/hBN/graphene (Gr/hBN/Gr) heterojunctions are attached to the surface of two square holes in the PCF to make one of the polarizing modes attenuate significantly. The tunability of the Fermi level (EF) in Gr/hBN/Gr enables the proposed device to function as a polarizer or a polarization-maintaining fiber. The combination of PCF's endless single-mode feature and graphene's broadband optical response feature enables the fiber polarizer to exhibit a wide spectrum range with single-mode transmission characteristics.

A Novel High Birefringence Single Elliptic Photonic Quasicrystal Fiber

This A novel single elliptical photonic quasi-crystal fiber (PQF) structure based on ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) is proposed. There is a single elliptical air hole at the fiber core and a ten-fold Person-type quasi-crystal structure distributed in the outer layer. The birefringence and confinement loss (CL) of the PQF are numerically proposed in short-wavelength infrared region (SWIR) based on finite element method. The high birefringence is achieved thanks to a single ellipse near the fiber core breaking the symmetry of the structure. Fluoride materials ZBLAN have lower CL in SWIR than traditional quartz glass. The birefringence of this novel PQF can be maintained above 10-2, which will have great potential in optical devices.

The electronic structure and optical properties of BaBiBO4, a promising compound with high birefringence

Birefringence is a crucial parameter for various advanced optical devices like birefringent crystals, and nonlinear optical materials. In this paper, the electronic structures and optical properties of centrosymmetric BaBiBO4 are investigated using the first-principles method. The results show that BaBiBO4 could be a good birefringent compound whose birefringence is 0.195 @ 1064 nm and 0.266 @ 532 nm. The spin–orbit-coupling effect plays an important role in electronic structures, leading to downshift and band splitting of the conduction band, resulting in a reduced bandgap of 3.32 eV and enhanced birefringence. The projected density of states and real-space atom-cutting results reveal that BiO5 groups with asymmetric distribution of stereochemical active lone pairs and the staggered parallel arrangement of the BO3 groups give the main contribution to birefringence.

Hybrid Anapole Induced Chirality in Metasurfaces.

The interaction between light and matter, particularly chirality, plays a pivotal role in modern science and technology. Typically, metasurfaces achieve chiro-optical effects by coupling electric and magnetic dipoles in specific orientations. In this work, the design and optimization of an asymmetric H-shaped metasurface is explored to induce hybrid anapole (HA) for optical activity. When the symmetry of the metasurface structure is disrupted, the design can simultaneously excite first-order and pseudo high-order HA under illumination with a specific circular polarization, both occurring within the same spectral regime. This results in high reflection for one circular polarization and a significant reduction in reflection for the orthogonal polarization, thereby exhibiting exceptional chiro-optical activity. Moreover, the HA-based chiral metasurface demonstrates strong polarization control capabilities, as verified by Stokes parameter analysis, revealing high birefringence and a pronounced dependence on the incident polarization angle. These results provide valuable insights for the design and optimization of HA metasurfaces for advanced optical applications and polarization control, paving the way for new developments in chiral nanophotonics.

High birefringent slotted core slotted cladding porous core PCF for THz waveguide

A novel design featuring a porous core photonic crystal fiber (PC-PCF) is proposed in this paper for terahertz (THz) waveguide application. This work uses finite element method (FEM) and a boundary condition related to perfectly matched layer (PML) for analyzing the guiding properties. This methodology is supported by a fiber type featuring a slotted core and slotted cladding, utilizing Zeonex as the material. It offers high birefringence valued at 0.0978, small confinement loss of 10−14 dB/cm, a meager amount of effective material loss (EML) valued at 0.011697 dB/cm and a very high core power fraction (CPF) of 67.156%. Additionally, it shows a flattened pattern of dispersion measuring 0.4 ± 0.2 ps/THz/cm at an extensive frequency range of 0.5 THz to 2 THz. Other significant waveguide properties: effective refractive index, numerical aperture (NA), V-parameter, effective area, spot size, and beam divergence of the suggested fiber are numerically analyzed and conferred thoroughly. Regarding its mode of operation, the proposed fiber primarily functions in multimode, but it can also operate in single mode for higher porosity levels and lower core diameters. This unique characteristic renders the proposed PC-PCF structure well-suited for a broad range of applications, offering versatility as to its mode of operation.

Yb-doped tapered double-clad fibers with polarization maintenance for half-kW power amplifiers.

Amplifying short pulses directly within a single fiber laser system has proven to be a challenging task, primarily due to thermally induced transverse mode instabilities and detrimental nonlinear effects. Another demanding aspect is preserving the linear polarization state at high power levels, which is even more pronounced for ultra-large-mode area fibers. This study demonstrates significant advancement in the direct amplification of narrow linewidth short pulses from tens of mW to several hundreds of Watts in a single-stage amplification, maintaining a high degree of linear polarization at the maximum output power. Through a comprehensive experimental investigation, two distinct types of Ytterbium-doped tapered double-clad fibers (T-DCFs), namely, PANDA (PT-DCF), with high built-in birefringence, and spun (sT-DCF), with ultra-low built-in birefringence, are examined. The unique geometrical architecture of the amplifiers is exploited for the realization of a compact and highly efficient picosecond fiber-based laser system, achieving more than 75% slope efficiency. In a single amplification stage, 50 ps pulses at a repetition rate of 20 MHz and an average power of 65 mW are amplified up to 457 W and 573 W of average power using PT-DCF and sT-DCF amplifiers, respectively. Both amplifiers exhibit near diffraction limited beam quality, M2 < 1.4 at the highest power level. At the maximum power levels, the system maintains a high degree of linear polarisation, achieving ∼ 90% and ∼ 94% for the sT-DCF and PT-DCF, respectively. These ultra-large mode area fiber amplifiers are verified as versatile solutions for direct amplification of short pulses up to half-kW level with excellent spectral, spatial, and polarization characteristics.

Robust flexible hollow racetrack-shaped terahertz waveguide with single-polarization single-mode and low-loss by plasma aided hot-pressing method

A flexible single-polarization single-mode (SPSM) polymer/Ag-coated hollow waveguide with a racetrack-shaped cross-section was designed and prepared using a simple hot-pressing method and plasma treatment. The waveguide structural parameters were numerically optimized using the finite element method and the SPSM transmission can be achieved in a high birefringent (>0.8) hollow racetrack-shaped waveguide (HRW). The racetrack-like waveguides were facilely prepared by hot-pressing commercially available circular acrylonitrile butadiene styrene (ABS) and poly-ether-ether-ketone (PEEK) tubing, followed by plasma treatment and silver-plating. The HRW samples with a length of 40 cm were prepared, with a straight transmission loss of 1.74 and 1.68 dB/m at 0.1 THz, respectively, and the polarization degree is 99.9 %. When bent for 120° at a 10 cm radius or twisted by 90°, the waveguide samples have additional losses less than 0.22 and 0.14 dB/m, respectively, while the polarization degrees keep almost unchanged. After 200 h hydrothermal aging (85 RH%, 85 ℃) and 20 times high (85 ℃)/low (−40 ℃) temperature tests, the loss increase is less than 0.14 dB/m and the polarization degree remains unaffected. The HRW could be used in practice as a competitive substitute for traditional rectangular metal waveguides due to its high SPSM performance, lightweight, robustness, flexibility, and easy fabrication.

Effect of lateral substituents on the properties of polymerisable liquid crystals with bistolane core

ABSTRACT A new series of polymerisable liquid crystals based on bistolane core and different lateral substituent groups (F, Cl, CH3 and C2H5) were synthesised and characterised by1H-NMR and13C-NMR. The properties of these compounds were tested by DSC, POM and Abbe refractometer. The results indicate that all of these compounds display a stable nematic phase, and the introduction of lateral substituents has a significant impact on the phase behaviour and birefringence. As the size of lateral substituents gradually increases the clearing point and birefringence of the liquid crystals both show a decreasing trend. The birefringence of these new compounds reaches 0.36 ~ 0.49, which is about 2 ~ 3 times that of the commercial compounds RM257. These new polymerisable liquid crystals with extremely high birefringence provide a choice for developing devices based on planar optics.

Optimization of low-loss, high birefringence parameters of a hollow-core anti-resonant fiber with back-propagation neural network assisted hyperplane segmentation algorithm.

In engineering, optimizing parameters often involves computationally expensive tasks, especially when dealing with multi-dimensional variables and multiple performance metrics. This falls under the category of multi-objective black-box optimization. To address this, we propose two optimization algorithms for low and medium-dimensional spaces, incorporating relaxation conditions for hyperplane segmentation. For the specific parameter optimization of HC-ARF, we employed a two-stage approach. It combines a BP neural network as a surrogate model with a hyperplane separation optimization algorithm. This method efficiently optimizes both confinement loss (CL) and birefringence, using a weighted sum approach to identify their Pareto sets. We validate the effectiveness and stability of the surrogate model by comparing it with traditional optimization algorithms. Exhaustive experiments confirm the superiority of this algorithm and the results show that our optimized structure achieves impressive performance metrics, including a loss of 0.8 dB/m, a birefringence of 2.2×10-4, and a critical bending radius of 0.5 cm under optimal parameters.

Birefringence and Orientation Direction Control of Photoalignable Liquid Crystalline Copolymer Films Based on In Situ Modification of Mesogenic Groups.

Controlling the birefringence of optical films is imperative to fabricate thin birefringent optical devices. Here, new photoalignable liquid crystalline copolymers (PLCPs) with 4-formylphneyl benzoate (PA) and cinnamic acid (CA) side groups are synthesized, which attain high photoreactivity and controllability of the orientation direction. Additionally, the exposed films are treated with 2-aminofluorene (AF) for an in situ condensation of PA with AF to form a Schiff base with a high inherent birefringence. Birefringence of the photoaligned film can be controlled up to 0.45 without disturbing the photoinduced orientation structure.