High Birefringence Research Articles

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 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.

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.

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.

New Series of Hydrogen-Bonded Liquid Crystal with High Birefringence and Conductivity.

Liquid crystals with high dielectric anisotropy, low operational thresholds, and significant birefringence (Δn) represent a key focus in soft matter research. This work introduces a novel series of hydrogen-bonded liquid crystals (HBLCs) derived from 4-n-alkoxybenzoic, 4-alkoxy-3-fluorobenzoic derivatives (nOBAF), 4-alkoxy-2,3-fluorobenzoic derivatives (nOBAFF), and 2-fluoro-4-nitrobenzoic acid. The HBLCs were characterized using Fourier transform infrared spectroscopy, and their thermal behavior was evaluated via differential scanning calorimetry. Optical observations were conducted using polarized optical microscopy. The results indicate that mixtures containing benzoic acid with a bilateral fluorine substituent exhibit both SmA and SmC phases, while those with a unilateral fluorine substituent exhibit nematic and SmA phases. Moreover, an increase in the length of the alkoxy chain results in an expanded mesophase temperature range. This study demonstrates that the presence of a fluorine substituent and the incorporation of an NO2 group in the molecular structure result in an increase in dielectric permittivity, DC conductivity, dielectric anisotropy, and birefringence.

Design and Study of Low Loss, High Birefringence Quasi-Symmetric Hollow-Core Anti-Resonant Fiber

Design and Study of Low Loss, High Birefringence Quasi-Symmetric Hollow-Core Anti-Resonant Fiber

Highly birefringent anti-resonant hollow-core fiber with meniscoid nested structure.

We propose a meniscoid nested anti-resonant hollow-core fiber (MAF), wherein the fourfold rotational symmetry structure enables high birefringence and low loss in dual-wavelength range. Numerical investigation and simulation for variations in wall thickness along orthogonal directions are conducted, through which a formulated optimization criterion revealing the relationship between minimum difference in wall thickness and birefringence of 10-5 is obtained. A parameter of beat length to loss ratio η is defined to evaluate MAF performance with respect to birefringence and confinement loss (CL). With optimized MAF structure, the birefringence and CL are improved to 3.62 × 10-5 and 8.5 dB/km at 1.06 µm, 9.83 × 10-5 and 204.1 dB/km at 1.55 µm, respectively. Meanwhile, the bandwidths extend to 172 nm at 1.06 µm and 216 nm at 1.55 µm, and the superior bending resistance characteristics are validated. Our work offers valuable guidance for designing and optimizing highly birefringent anti-resonant hollow-core fiber (ARF), and the proposed MAF has great potential in polarization-dependent transmission and interferometric fiber gyroscopes.

Anti-Resonant Hollow-Core Fibers with High Birefringence and Low Loss for Terahertz Propagation

A new type of anti-resonant hollow-core fiber for terahertz waveguides is proposed. By introducing central support pillars and an elliptical structure, the fiber achieves high birefringence while maintaining low confinement loss and low material absorption loss. The fiber structure is optimized through simulation using the finite element method. The optimized fiber exhibits a birefringence of up to 1.22 × 10−2 at a frequency of 1 THz, with a confinement loss of 8.34 × 10−6 dB/cm and a material absorption loss of 7.17 × 10−3 dB/cm. Furthermore, when the bending radius of the fiber is greater than 12 cm, the bending loss of the anti-resonant optical fiber at 1 THz is less than 1.36 × 10−4 dB/cm, demonstrating good bending resistance and high practical value. It is expected to play a significant role in optical communication systems.

Study on mode properties of GaAs-based hybrid plasmonic terahertz waveguides

Terahertz (THz) fields are increasingly being used to address the critical challenges associated with achieving high data rates and rapid communication. In this study, a hybrid plasmonic THz waveguide is designed and analysed operating in the 2.5–3.5 THz frequency range. The waveguide is constructed using gallium arsenide as the high-refractive-index core, surrounded by aluminium arsenide and silver placed on a high-density polyethylene (HDPE) substrate. Graphene is strategically positioned between the HDPE layers to enhance light confinement. The mode properties of the proposed waveguide are simulated with Comol Multiphysics using the finite-element method and show unique characteristics. Observation of the simulated results at 2.5–3.5 THz reveals a high effective refractive index of 3.79, a maximum effective mode area of 1.88 mm2, a high birefringence of 0.2, a low dispersion of 0.10 ps THz−1 cm−1, a high mode field diameter of 15.8 mm, a high beat length of 123 mm and a low confinement loss of 1.79 × 10−9 mm−1. These features make the proposed waveguide suitable for applications in photonic integrated circuits for THz communications.

A silicon nitride (Si3N4) filled PCF containing high birefringence and nonlinearity for optical applications

A silicon nitride (Si3N4) filled PCF containing high birefringence and nonlinearity for optical applications

Highly anisotropic and stretchable birefringent elastomers for multicolored strain displays

The birefringent response of elastomer materials with rich polarized interference colors is promising in the field of stretchable optical areas. Increasing the accessible change number of interference colors during stretching birefringent materials is important for optical strain display. Here, we can fabricate birefringent elastomers with multicolor response of polarized interference color via compositing with highly oriented cellulose nanocrystals (CNCs), transparent one-dimensional biomass nanocrystals with excellent birefringent properties, which exhibit sensitive, reversible, and controllable changes of interference color during stretching in perpendicular to the orientation of the CNCs. Employing a layer-by-layer shearing process of CNC aqueous dispersion, solvent exchange of monomers, and in-situ polymerization, we can produce birefringent elastomers with high optical path difference (>1500 nm) due to the high birefringence (2.81 × 10−3) and high thickness (within 1 mm). In addition, the high retardation of the birefringent elastomers is conducive to more interference color changes when stretching perpendicularly to the direction of oriented CNCs. Then, we demonstrate this birefringent material capable of fabricating a polarized-optical strain display by utilizing the multicolored responses during the stretching process.

High birefringence low loss nearly zero flat dispersion similar to slotted core photonic crystal fibers

Abstract Studying high-performance photonic crystal fibers (PCF) is of significant scientific importance for terahertz (THz) waveguide systems. This study introduces a novel PCF design with a core composed of the smallest sub-wavelength units resembling a slotted structure, aiming to achieve high birefringence and low loss. The optical properties of the proposed PCF are analyzed through simulations, yielding impressive results. The PCF exhibits an ultra-high birefringence of 0.07848, a minimum limiting loss of 10−17 dB/cm, and an effective material loss as low as 0.04251 cm−1. Moreover, it demonstrates near-zero flat dispersion of −0.012 ± 0.074 ps/THz/cm over a broad frequency range of 1.2–2.2 THz. This fiber stands out by not only providing high birefringence but also by striking an optimal balance among birefringence, transmission loss, and dispersion for THz waveguides. The implications of this work are profound for the development of THz communication systems, THz polarization-maintaining transmission, and sensing applications. Furthermore, it established an important benchmark for the design of THz-PCFs that prioritize high birefringence, low loss, and near-zero flat dispersion, offering an essential reference for future research and development in this field.