Birefringence Properties Research Articles

Effect of Titanium Oxide (TiO2) Nanoparticles on the Opto-Mechanical Properties of Polyethylene Terephthalate (PET) Fibers

Polyethylene terephthalate (PET) is widely used in various applications due to its excellent mechanical properties and chemical resistance. However, PET fibers still lack specific features and functionalities that can be improved via nano-additives, particularly metal oxides. In this study, we investigate the effect of adding TiO2 nanoparticles to PET to form PET/TiO2 fibers and examine their opto-mechanical properties. This study utilizes optical interferometric techniques to assess how mechanical stretching influences the optical and mechanical properties of PET fibers treated with TiO2 nanoparticles. A Mach–Zehnder interferometric setup, integrated with a versatile device capable of mechanically stretching samples, is used to achieve this task. Variations in refractive index and birefringence along the longitudinal axis of undrawn and drawn PET/TiO2 fibers are examined. The research meticulously explores the fluctuations and spatial variations in the refractive index and birefringence properties, exhibiting anisotropy in optical behavior, along the longitudinal axis of unstretched and stretched PET/TiO2 fibers. The findings and outcomes derived from this comprehensive study provide substantive information that can facilitate the enhancement and optimization of the coupled optical and mechanical properties of materials explicitly engineered for advanced applications.

LaAgSiS4: Increasing Optical Birefringence in Rare Earth Chalcogenide by Addition of Planar [AgS3] Groups.

Optoelectronic materials with excellent birefringent properties are of significant importance in the fields of optical communications and laser technology. Recently, rare earth (RE) chalcogenides with anisotropic [RESn] groups have been proven to be high-performance infrared birefringent materials. Herein, we demonstrate that the addition of planar groups can further increase the birefringence in RE chalcogenides, as realized by incorporating planar [AgS3] groups into the RE-I-IV-S4 family for the first time. The newly obtained LaAgSiS4 compound shows higher polarity anisotropy than its homologue LaLiSiS4 and LaKSiS4, which resulted in a larger birefringence (0.12@600 nm) at least twice as large as that of the latter two compounds (0.05/0.06@600 nm). The structure-property relationship of LaAgSiS4 was investigated through structural analysis and first-principles calculations. The results indicate that the increased optical birefringence in LaAgSiS4 originates from the synergic effects of the distorted [LaSn] polyhedra and planar [AgS3] triangles. This work provides an effective strategy for enhancing optical birefringence in IR chalcogenides.

Minimize flow-induced uncertainty in polarization sensitive optical coherence tomography imaging using eigen decomposition.

Blood flow alters the scattering behavior of penetration light, causing instability in the polarization state to emerge at the underlying tissue during polarization-sensitive optical coherence tomography (PSOCT). We propose an eigen decomposition method to meet this challenge, where the static and dynamic scattering signals are separated for PSOCT to provide the polarization measurements of the tissue of interest that is located beneath the blood flow. Using flow phantoms made by Intralipid solution and 3D-printed birefringent material, we show the flow-induced effects on the measurements of sample birefringent properties of optical axis, phase retardation, and degree of polarization uniformity. We demonstrate the usefulness of the proposed method through in vivo imaging of the human nail fold.

Measuring linear birefringence via rotating-sample transmission Stokes spectropolarimetry

Linear birefringence is a fundamental property of optically anisotropic media, defined by the difference in refractive index experienced by light polarized along orthogonal directions. It is usually manifested in microscopically aligned molecular systems, where a preferential direction of light–matter interaction is created. For instance, the anisotropic structure of calcite crystal causes the famous double-refraction phenomenon. Another common example is commercial adhesive tapes, which are polymeric materials possessing birefringent properties due to their manufacturing processes. The intrinsic relation between birefringence and molecular alignment forges a new analytical route to study materials such as polymeric thin films. Therefore, the capacity of measuring linear birefringence and its fast axis is of paramount importance for the science of anisotropic molecular systems. In this contribution, a comprehensive approach to acquire linear birefringence using rotating-sample transmission Stokes spectropolarimetry is presented and applied to transparent adhesive tapes as a case study. The experimental setup comprises a thermal light source and a spectropolarimeter capable of determining wavelength distributions of Stokes parameters. The samples are carefully aligned in a rotating mount and subjected to a fixed broadband vertically polarized light beam. Then, the transmitted light is analyzed using a rotating retarder type of spectropolarimeter. Through systematic variation of the sample’s angular position, the Stokes parameters of transmitted light are measured for each transmitted wavelength as a function of the sample’s angular position. The linear retardance and fast axis direction relative to the tape’s long axis are then determined from the modulation of Stokes parameters over sample rotation. The model derivation, experimental procedure, and signal processing protocol are described in detail, and the approach is verified with a simple correlation between linear retardance and the number of stacked layers of tape.

Na(C2H10N2)2[Zn3(PO4)2(H0.5PO4)]2: A Short-Wave Ultraviolet Open-Framework Zincophosphate Exhibiting Substantial Optical Dispersion Ability.

The exploration of short-wave ultraviolet (SUV; λ < 280 nm) transparent phosphates with substantial birefringence is crucial for the advancement of SUV laser industry. Despite their SUV transparency and potential for constructing materials with large birefringence, open-framework (OF) phosphates have rarely been explored for their birefringent properties. Herein, through a systematic exploration in this field, a new ethylenediamine-based OF zincophosphate, Na(C2H10N2)2[Zn3(PO4)2(H0.5PO4)]2 (NEZPO), has been developed. NEZPO exhibits remarkable SUV transparency and significant birefringence (Δn = 0.060 at 546 nm), highlighting the potential for the development of benign SUV crystals within the OF phosphates family.

(Cd)SO4 doping on L-Valine crystal for the enhancement of opto-electronic and laser properties

L-Valine is a good molecular platform to induce NLO properties for Laser application and considerable laser properties can be improved by injecting suitable electron administrated substitutional groups. This work is an attempt to make laser properties enhancement by increasing Cd solvent concentration on L-Valine compound. The recorded XRD peaks addressed the significant increment of laser properties of the composite crystal. The results obtained for pure L-Valine was; a=5.221 (Å), b=6.910 (Å) and c=4.994 (Å) and associated indices of refraction was n1=1.511, n2=1.583 and n3=1.599. The results of 2% CdSO4; a=5.580 (Å), b=7.011 (Å) and c=5.091 (Å) and associated indices of refraction was n1=1.561, n2=1.612 and n3=1.633. For 5% CdSO4; a=5.599 (Å), b=7.831 (Å) and c=5.659 (Å) and associated indices of refraction was n1=1.588, n2=1.661 and n3=1.699. For 10 % CdSO4; a=5.592 (Å), b=7.612 (Å) and c=5.822 (Å) and associated indices of refraction was n1=1.661, n2=1.693 and n3=1.593. For 15 % CdSO4; a=5.551 (Å), b=6.332 (Å) and c=4.734 (Å) and associated indices of refraction was n1=1.501, n2=1.599 and n3=1.593. The non linear refractive index was changed from 3.891 X 10-8 cm2/W to 4.231 X 10-8 cm2/W for 2%, 5%, 10% respectively and Third order non linear optical susceptibility (χ(3)) was ranged from 4.621X10‑6 esu to 5.091X10‑6 esu. The restored chemical potential for non linear optical (NLO) and birefringence properties was found to be improved. The scattering capability of homo nuclear and hetero nuclear bonds along with the CdSO4 voids was identified for attaining non linear scattering process.

Nanocolumnar Metamaterial Platforms: Scaling Rules for Structural Parameters Revealed from Optical Anisotropy

AbstractNanostructures represent a frontier where meticulous attention to the control and assessment of structural dimensions becomes a linchpin for their seamless integration into diverse technological applications. However, determining the critical dimensions and optical properties of nanostructures with precision still remains a challenging task. In this study, by using an integrative and comprehensive methodical series of studies, the evolution of the depolarization factors in the anisotropic Bruggeman effective medium approximation (AB‐EMA) is investigated. It is found that these anisotropic factors are extremely sensitive to the changes in critical dimensions of the nanostructure platforms. In order to perform a systematic characterization of these parameters, spatially coherent, highly‐ordered slanted nanocolumns are fabricated from zirconia, silicon, titanium, and permalloy on silicon substrates with varying column lengths using glancing angle deposition (GLAD). In tandem, broad‐spectral range Mueller matrix spectroscopic ellipsometry data, spanning from the near‐infrared to the vacuum UV (0.72–6.5 eV), is analyzed with a best‐match model approach based on the anisotropic Bruggeman effective medium theory. The anisotropic optical properties, including complex dielectric function, birefringence, and dichroism, are thereby extracted. Most notably, the research unveils a generalized, material‐independent inverse relationship between depolarization factors and column length. It is envisioned that the presented scaling rules will permit accurate prediction of optical properties of nanocolumnar thin films improving their integration and optimization for optoelectronic and photonic device applications. As an outlook, the highly porous nature and extreme birefringence properties of the fabricated columnar metamaterial platforms are further explored in the detection of nanoparticles from the cross‐polarized integrated spectral color variations.

Origin of the anisotropic Beer–Lambert law from dichroism and birefringence in β -Ga2O3

The anisotropic optical absorption edge of β-Ga2O3 follows a modified Beer–Lambert law having two effective absorption coefficients. The absorption coefficient of linearly polarized light reduces to the least absorbing direction beyond a critical penetration depth, which itself depends on polarization and wavelength. To understand this behavior, a Stokes vector analysis is performed to track the polarization state as a function of depth. The weakening of the absorption coefficient is associated with a gradual shift of linear polarization to the least absorbing crystallographic direction in the plane, which is along the a-exciton within the (010) plane or along the b-exciton in the (001) plane. We show that strong linear dichroism near the optical absorption edge causes this shift in β-Ga2O3, which arises from the anisotropy and spectral splitting of the physical absorbers, i.e., excitons. The linear polarization shift is accompanied by a variation in the ellipticity due to the birefringence of β-Ga2O3. Analysis of the phase relationship between the incoming electric field to that at a certain depth reveals the phase speed as an effective refractive index, which varies along different crystallographic directions. The critical penetration depth is shown to be correlated with the depth at which the ellipticity is maximal. Thus, the anisotropic Beer–Lambert law arises from the interplay of both the dichroic and birefringent properties of β-Ga2O3.

(Invited) High Temperature Exciton Properties in Aggregated Single-Walled Carbon Nanotubes

Individual single-walled carbon nanotubes (SWCNTs) at high temperatures have been reported to generate narrow-band thermal radiation in the near-infrared region due to thermally robust excitonic effects [1,2]. This phenomenon potentially offers a new opportunity for utilizing exciton properties in thermal engineering such as thermophotovoltaic energy harvesting requiring excellent wavelength selective near-infrared thermal emitter. However, for its realistic applications in macroscale, it is necessary to make the distinct exciton effect available under high temperature conditions in macroscopic assemblies of SWCNTs. As a first step toward this goal, we have recently determined broadband complex refractive index spectra of single-chirality SWCNT membranes in which SWCNTs are aligned two-dimensionally in a plane [3] and reported their birefringent properties [4]. In the presentation, we will discuss the change in the optical spectra of SWCNT assemblies with increasing temperature, as well as how the aggregation states affect the exciton properties. [1] T. Nishihara, A. Takakura, Y. Miyauchi, and K. Itami, Nat. Commun. 9, 3144 (2018). [2] S. Konabe, T. Nishihara, and Y. Miyauchi, Opt. Lett. 46, 3021 (2021). [3] T. Nishihara, A. Takakura, M. Shimasaki, K. Matsuda, T. Tanaka, H. Kataura, and Y. Miyauchi, Nanophotonics 11, 1011 (2022). [4] H. Wu, T. Nishihara, A. Takakura, K. Matsuda, T. Tanaka, H. Kataura, and Y. Miyauchi, Carbon, in press.

Characterization of polarization properties of colorectal cancer using decomposition Mueller matrix method

Rectal cancer is the third most prevalent cancer diagnosed and is traditionally screened using colonoscopy. Meanwhile, polarization characteristic measurement has emerged as an attractive alternative in recent years owing to its deep analysis of the structure of samples and non-invasive nature. Accordingly, this study employed the Mueller matrix decomposition method to measure the effective optical parameters of 100 slices from 20 healthy rectal tissue samples and 100 slices from 20 cancerous rectal tissue samples. The mean values and expression levels of the linear birefringence, circular birefringence, linear dichroism, circular dichroism, and depolarization index properties of the samples were compared using t-tests and ANOVA tests. The experimental results showed that the linear birefringence, orientation angle of linear dichroism, and values of linear dichroism and circular dichroism showed significant differences between the different tissue types. Thus, these parameters may serve as useful biomarkers for the diagnosis of rectal cancer.

Characteristics Of Partially Pregelatinized Sago Starch Extruded Under Various Conditions Using A Twin Screw Extruder Without A Die

Abstract This study aims to obtain the characteristics of PPSS as a binder extruded in a twin-screw extruder (TSE) without a die under 9 extrusion conditions selected from a systematic review. The Successive conditions: moisture content, last zone of barrel temperature, and screw speed for each condition were recorded. Respectively, the values were 32%, 60⁰C, 100 rpm for PPSS 1; 22%; 120⁰C; 250 rpm for PPSS 2; 22%, 100⁰C, 250 rpm for PPSS 3; 16%, 135⁰C, 150 rpm for PPSS 4; 10%, 160⁰C, 200 rpm for PPSS 5; 28.8%;, 100⁰C, 220 rpm for PPSS 6; 30%, 80⁰C, 200 rpm for PPSS 7; 25.2%, 97.5⁰C, 250 rpm for PPSS 8, and 30%; 135⁰C; 160 rpm for PPSS 9. The study informed that the degree of gelatinization (DG), water solubility index (WSI), water absorption index (WAI), and swelling power (SP) of PPSS 6 were the highest among the others but its bulk density (BD), degree of whiteness (DW), maximum viscosity (MV), and enthalpy were the lowest. Scanning electron microscopy showed that PPSS granules were irregular compared to their natural oval shape. Starch granule crystallinity indicated that some crystallines became amorphous and some increased (PPSS 3 and 4) while birefringence properties almost disappeared entirely.

Homoatomic Polychalcogenide Nonlinear Optical Anionic Groups with Ultra-Large Optical Anisotropy.

Functional assembly of nonlinear optical (NLO) motifs with a large optical anisotropy is vital to the development of advanced NLO and birefringent materials. In this work, we highlight that, in addition to heteroatomic NLO motifs, homoatomic anionic clusters formed by aggregated anions (S, Se, Te) exhibit diverse chain-, ring-, and cage-like chemical structures as well as one-, two-, and three-dimensional motif alignments. The rich structural chemistry enables homoatomic polychalcogenides (HAPCs) to exhibit asymmetric structural features and anisotropic optical properties, with great potential for NLO and birefringent performance. Focusing on totally 55 binary HAPCs A2Qn (n = 2, 3, 4, 5; A = Na, K, Rb, Cs; Q = S, Se, Te) and their ternary analogues, we employ the state-of-the-art first-principles approach to systematically investigate the modulation evolution of their NLO and birefringent properties. Remarkably, Rb2Te3 and Na2TeSe2 exhibit rarely colossal birefringence (>1.0@10 μm) and NLO effects (>20 × AgGaS2), much larger than conventional NLO chalcogenides. Na2Te3 presents the largest birefringence to date (∼3.48@1, 2.72@2, 2.34@10 μm), indicating the unique structural superiority of HAPC in terms of ultra-large birefringence. By mining the intrinsic mechanism, the HAPC anionic groups are identified as novel mid-infrared NLO "material genes", furnishing unique NLO and birefringent performance for the design of novel optoelectronic materials.

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.

Phase Transitions and Nonlinear Optical Property Modifications in BaGa4Se7.

Phase transitions can change the crystal structure and modify the physical properties of crystals. In this work, we investigate the phase transition behavior in BaGa4Se7, an important middle infrared (mid-IR) nonlinear optical (NLO) crystal, in the temperature range from room temperature to 1173 K. Interestingly, the BaGa4Se7 crystal undergoes a reversible ferroelastic phase transition at T = 528 K, resulting in the presence of a newly discovered phase (γ-phase) at the higher temperature. The experimental temperature dependence of optical birefringence, as well as the first-principles birefringence and NLO coefficients, reveals that the γ-phase exhibits larger birefringence and better NLO properties compared with those of the low-temperature phase (α-phase). This work demonstrates that phase-transition-induced structural modification can improve the mid-IR NLO properties, which would provide an effective avenue to obtain materials with good optoelectronic performance.

Design, synthesis and characterization of high refractive index aromatic polyesters containing fluorene and thioether groups

9,9-bis(4-hydroxyphenyl)fluorene (BPF) is a highly structurally symmetric bisphenol with excellent optical properties of low birefringence and high refractive index, however, the glass transition temperature ( Tg) of its polyester is high ( Tg&gt;300°C), which makes it difficult to be thermally processed and limits its application. On the other hand, 4,4′-Thiobis (2-methylphenol) (T2MP) has a flexible thioether group, its introduction not only brings high refractive index, but also can appropriately reduce the Tg of the polymer. Therefore, by combining the advantages of both of them, we prepared aromatic polyesters with high refractive index and stabilization. This study provides a route that can appropriately reduce Tg without loss of refractive index.

Slab waveguide communication study using Finite Difference Method (FDM) with fourth-order compact scheme

An accurate and efficient semi-vectorial mode solver, examining Electric (E) and Magnetic (H) fields, is utilized to explore the communication characteristics of various slab waveguides. This approach relies on the Finite Difference Method (FDM) using uniform grid points, employing a Higher (Fourth) Order Compact type technique coupled with Conjugate Gradient (CG) iteration. The present study is an extension of the previous work where various aspects of E- and H-field propagations through rib-strucured waveguide was analyzed successfully. By incorporating the refractive index profile of the slab structure, excellent functionality of the waveguide is demonstrated here in Electric field by utilizing the concepts of normalized index and effective or modal index, confinement factor, and the modal birefringence properties which proves to be critical for potential applications in photonic integrated circuits. The materials chosen for the purpose are AlGaAs-GaAs and GeSi which play a vital role in characterizing the waveguides’performances through simulation using MATLAB. The use of surface and contour plots aids in visualizing the distribution of corresponding field within the guided modes. This analysis significantly contributes in understanding the waveguide's behavior and confinement capability during the field propagation. Most importantly, the variations of the waveguides’performance indices with their structure parameters help to identify their optimized values for fabrication to enhance the transmission efficiency of the waveguide.

Characterization of Physicochemical Properties of Annealed Corn Flour and Starch: A Verification of Meta‐Analysis

AbstractThis study examines the effects of annealing process (temperature 50 °C, moisture content of 80%, for 20 h) on physicochemical characteristics (proximate composition, content of resistant starch (RS) and amylose, degree of starch digestibility, shape and size of starch granules, crystallinity, and starch gelatinization profile) of corn flour and corn starch. Two stages of experiment are as follows: 1) verifying the results of the meta‐analysis of corn starch and flour modification by annealing method and 2) analyzing their physicochemical properties. As a result, annealing significantly improves RS content in both groups, reaching 14.18% in annealed corn flour (AF) (compared to 3.27% in native corn flour (NF)) and 21.87% in annealed corn starch (AS) (compared to 3.82% in native corn starch (NS)). The present work also confirms that the treatment unaltered birefringence properties of all samples. Moreover, pasting properties of corn starch and flour demonstrate remarkable changes. The peak viscosity of AS and NS is higher than AF and NF. In addition, gelatinization seems to occur at similar temperature, but needs extra time for starting gelatinization. XRD analysis reveals A‐type crystalline for all samples, while FTIR analysis evidenced that annealing process alters the regions of amorphous and crystalline.

External electric field assisted energy band gap modulation and optical properties of SiGe/AsSb heterobilayers

In this work, first-principle calculations within Density Functional Theory (DFT) were performed to study the structural, electronic, and optical properties of eight different bilayer van der Waals (vdW) heterostructures composed of SiGe and AsSb monolayers. These heterobilayers exhibit large energy bandgap (90 meV–459 meV) with linear energy–momentum relationship, implying high charge carrier mobility. Application of external vertical electric field can effectively modulate the energy bandgap of these heterobilayers from 64 meV to 459 meV, depending on stacking orders. Our study shows that a moderate amount of electric field can almost linearly tune the energy bandgap, however, semiconductor to metal transition occurs beyond a certain limit. The mechanism of energy bandgap tuning by the external electric field was examined by studying differential charge density. The optical properties such as complex dielectric function, electron energy loss function, complex refractive index, reflectivity, absorption coefficient, and optical conductivity of these SiGe/AsSb heterobilayers are studied for parallelly and perpendicularly polarized incident light. Our research demonstrates that these heterostructures exhibit variable plasma frequency depending on the stacking order of the heterostructures, anisotropic reflectivity i.e., birefringence properties in response to the incident light's polarization. Also, they exhibit high refractive indices (∼3) and absorption coefficients (∼105 cm−1) from visible to ultraviolet incident light frequencies. Our study proposes several SiGe/AsSb heterobilayers with unique electronic and optical properties which may have potential applications in nanoscale electronic and optoelectronic applications.

Analysis of Polarization Angle on Holographic Recording Based on PQ/PMMA.

The polarization state of light waves significantly affects the quality of holographic recordings. This paper quantitatively analyzes the impact of different polarization states of signal and reference beams on the quality of holographic recordings in PQ/PMMA photopolymer systems during the holography process. By deriving the light field distribution of the interference between two light waves of different polarization states and introducing the interference fringe contrast and the modulation of the refractive index of the photopolymer, we established the relationship between the diffraction efficiency of PQ/PMMA photopolymer holographic gratings and the angle between polarization directions. Based on this relationship, simulations and experiments were conducted. The experimental results demonstrated that as the angle between the polarization directions increased, the diffraction efficiency of the material decreased, with the efficiency dropping to 24.69% of its original value when the angle increased from 0° to 50°. When the angle increased to 60°, the influence of polarization characteristics became gradually significant, and at 90°, it was entirely dominated by polarization characteristics. The photoinduced birefringence properties of the PQ/PMMA prepared in the measurement experiment were studied, and the polarization characteristics of the reconstructed light under polarization direction angles of 0°, 60°, and 90° were investigated. The results indicated that at a polarization direction angle of 60 degrees, the material exhibited a significant response to the polarization information of the signal light. Finally, holographic recordings of objects at different polarization direction angles were conducted, and the reconstructed images were used to visually reflect the impact of the polarization direction angle on the quality of holographic recordings.

Quantum imaging of biological organisms through spatial and polarization entanglement.

Quantum imaging holds potential benefits over classical imaging but has faced challenges such as poor signal-to-noise ratios, low resolvable pixel counts, difficulty in imaging biological organisms, and inability to quantify full birefringence properties. Here, we introduce quantum imaging by coincidence from entanglement (ICE), using spatially and polarization-entangled photon pairs to overcome these challenges. With spatial entanglement, ICE offers higher signal-to-noise ratios, greater resolvable pixel counts, and the ability to image biological organisms. With polarization entanglement, ICE provides quantitative quantum birefringence imaging capability, where both the phase retardation and the principal refractive index axis angle of an object can be remotely and instantly quantified without changing the polarization states of the photons incident on the object. Furthermore, ICE enables 25 times greater suppression of stray light than classical imaging. ICE has the potential to pave the way for quantum imaging in diverse fields, such as life sciences and remote sensing.