Optomechanical variations in cold‐drawn thermally treated polypropylene fibers

A two‐beam polarizing interference microscope with a microstrain device was used for measuring some optical and mechanical parameters for polypropylene (PP) fibers at room temperature (28 ± 1°C). The changes in the molecular orientation were evaluated to obtain orientation factors f₂(θ), f₄(θ), f₆(θ), 〈P₂(cos θ)〉, 〈P₄(cos θ)〉, and crystalline and amorphous orientation functions F_c and F_a, respectively. The shrinkage factor, uniaxial tension, true stress, molar refractivity R, surface reflectivity R′, the crosslink density N_s, the chain entanglement density N_c, the segment anisotropy γ_s, and the number of chains N′ were calculated. In addition, the shrinkage stress was found to increase with the increase of draw ratio. The dielectric constant ε, the dielectric susceptibility η, the average work per chain w′, and the constants of the stress–birefringence equation were obtained. Comparison between Hermans's optical orientation functions and the corrected formulas by de Vries are given. The values of fully oriented refractive indices n₁ and n₂ were found. The generalized Lorentz–Lorenz equation given by de Vries was used to determine the structural parameters of PP fibers. An empirical formula was suggested to correlate the changes in the evaluated parameters with different draw ratios, and its constants were determined. The study demonstrated changes on the molecular orientation factors and evaluated microstructural parameters as a result of an applied cold‐drawing process. Relationships between the calculated parameters and the draw ratios, together with microinterferograms were presented for illustration. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 729–738, 2003     

Magneto‐optical effects of Ge‐Ga‐Sb(In)‐S chalcogenide glasses with diamagnetic responses

The Faraday effects of Ge‐Ga‐Sb(In)‐S serial chalcogenide glasses were investigated at the wavelengths of 635, 808, 980, and 1319 nm, respectively. The compositional dependences were analyzed and associated influencing factors including the absorption edge, the concentration of Sb³⁺/In³⁺ ions, and the wavelength dispersion of refraction index were discussed. 80GeS₂·20Sb₂S₃ composition glass was found to have the largest Verdet constant (V=0.253, 0.219, 0.149, and 0.065 min·G^?1·cm^?1 for wavelengths 635, 808, 980, and 1319 nm, respectively) in these glasses, which is larger than that of commercial diamagnetic glasses (Schott, SF 6, V=0.069 min·G^?1·cm^?1@633 nm, for example). Sb³⁺ ions with high polarizability possessing s²‐sp electron jumps involving ¹S₀→¹P₁, ³P_0,1,2 transitions are responsible for large Verdet constant, and Becquerel rule is proved to be an effective guidance for estimating the Verdet constant and further optimizing the compositions in chalcogenide glasses.     

A novel chalcohalide fiber with high nonlinearity and low material zero-dispersion via extrusion

High nonlinear fibers with low zero-dispersion wavelength (ZDW), high laser power tolerance and large band-gap are urgent for all-optical-band supercontinuum (SC) generations. Widely used chalcogenide fibers usually have a large ZDW and low laser power tolerance, and thus are not ideal for such purpose. Here, an ultra-low material ZDW chalcohalide (ChH) glass fiber with high nonlinearity as well as high laser power tolerance has been fabricated successfully via a novel peeling-off-extrusion method. The step-index fiber has double-cladding structure, the inner cladding is GeGaSe-CsI glass and the outer one is GeSbS jacket. The core glass has an ultra-low material ZDW of 3.5 μm and large absorption edge of 2.0 eV. The nonlinear refractive index is 6.67 × 10⁻¹⁸ m²/W @1.55 μm. Broadband SC generation covering 1.05-13.0 μm is demonstrated in this novel ChH fiber. Such glass fiber with high nonlinearity, wide transparent range, low ZDW and high laser damage threshold is promising for the applications in the mid-infrared.     

Novel gallate-based oxide and oxyfluoride glasses with wide transparency,high refractive indices,and low dispersions

The glass-forming region of a BaO-La₂O₃-Ga₂O₃ ternary system was confirmed and BaF₂-BaO-La₂O₃-Ga₂O₃ new oxyfluoride glasses were prepared by a containerless processing. We also analyzed the physical, thermal, and optical properties of new oxide and oxyfluoride glasses. The direct effects of the substitution of oxygen by fluorine and the effect of BaO and La₂O₃ on the refractive index and Abbe number were discussed on the basis of electronic polarizability and resonance wavelength of oscillator. The refractive indices increased with increasing La₂O₃ concentration because La₂O₃ increased the electronic polarizabilities. Abbe number increased with increasing BaO and fluorine concentration because of the decrease in resonance wavelength of oscillator. By the combination of the BaO, La₂O₃, and fluorine in the gallate glass system, we could obtain novel oxide and oxyfluoride glasses with high refractive index (1.81-1.95) and high Abbe number (31-55). The absorption edge in UV region shifted to the shorter wavelength and IR cut-off wavelength shifted to the longer wavelength with increasing fluorine. Therefore, wide transparent glass was obtained from 262 nm to 11.3 μm.     

Role of tellurium addition on the linear and non-linear optical,structural, morphological properties of Ag60-xSe40Tex thin films for nonlinear applications

The tellurium (Te)-doped Ag_60-xSe₄₀Te_x (x = 0%, 5%, 10%, 15%) thin films of thickness ∼800 nm were prepared from the bulk sample by thermal evaporation method on a glass substrate. The X-ray diffraction study revealed the amorphous nature of the films whereas the change in vibrational modes was noticed from the Raman spectroscopy. The composition of the films was verified by energy dispersive X-ray analysis and the surface morphology pictures were taken by field emission scanning electron microscopy and atomic force microscope. The changes in optical properties (linear and non-linear) with Te addition were studied from UV-Visible spectroscopy data and related empirical formulas. The addition of Te reduced the bandgap values significantly and the reduction in transmission resulted in the increase of the linear refractive index. The decrease in optical bandgap is due to an increase in disorder while the width of the tail in the gap increased with Te%. The optical density, dispersion energy, extinction coefficient, carrier concentration, dielectric constant, oscillator wavelength increased while the oscillator energy, oscillator strength, optical electronegativity decreased with Te content. The electrical susceptibility increased with Te content. The non-linear susceptibilities and the non-linear refractive index increased which is good for the nonlinear photonic devices.     

Intrinsic second-order nonlinearity in chalcogenide glasses containing HgI2

Frequency conversion using nonlinear optical (NLO) crystals is widely used in advanced photonic technologies to produce coherent light in the spectral regions where the available laser sources are missing. Isotropic glasses usually do not show second order nonlinear processes like second harmonic or difference frequency generation (SHG, DFG) except for temporarily induced anisotropy under external stimuli. Here, we show that a HgI₂–Ga₂S₃–GeS₂ homogeneous glass exhibits a strong intrinsic SHG response comparable with that of the well-known NLO single crystal LiNbO₃. The origin of this extremely rare phenomenon seems to be noncentrosymmetric bent HgI₂ molecules embedded in a sulfide glassy host. Taking into account the unique properties of chalcogenide glasses (wide IR transmission, low phonon density, unlimited ability to be modified changing the appropriate glass properties, fiber drawing and thin layer design), the observed phenomenon opens up the possibility of creating fundamentally new devices for mid-IR photonics.     

Ga2S3‐Sb2S3‐CsI chalcohalide glasses for mid‐infrared applications

In this study, a new chalcohalide glass system, Ga₂S₃‐Sb₂S₃‐CsI, is reported. It has a glass‐forming domain composed of ~0‐35 mol% Ga₂S_3, ~15‐95 mol% Sb₂S₃, and ~0‐55 mol% CsI. The glasses have a wide transparent window of ~0.7‐13.5 μm, high third‐order nonlinear refractive indices of ~1.7‐8.7×10^?14 cm²/W @ 1.55 μm, and relatively short zero group‐velocity‐dispersion wavelengths of 3.8‐5.15 μm. The glasses can dissolve more than 2 mol% active ions (e.g., Dy³⁺), and the doped glasses show intense emissions in the mid‐infrared. These superior properties demonstrate their good potentials for mid‐infrared applications such as thermal imaging, nonlinear photonics and lasers.     

Effect of Sb addition on SbxSn1-xS thin films: The structural,morphological, and linear/nonlinear optical changes for optoelectronic applications

The current paper reports the changes in the structural and optical properties of antimony-doped tin sulfide ternary (Sb_xSn_1-xS) (x = 0, 0.05, 0.1, 0.15, 0.2) thin films synthesized by the thermal evaporation technique on a glass substrate. Structural characterization techniques such as X-ray diffraction and Raman spectroscopy of the prepared sample revealed that the thin films are crystalline in nature. The nanoflake-like structure was found from the surface morphological analysis performed by field emission scanning electron microscopy. The concentration of the compositional elements was confirmed from the energy dispersive X-ray analysis. The linear and nonlinear optical parameters were calculated by using the transmission data obtained from UV–vis spectroscopy in the range of 800–1100 nm. The optical measurements showed an increase in transmittance and shifting of the absorption edge. The optical bandgap increased (1.239–1.378 eV) and the refractive index decreased with the increase of Sb concentration, satisfying the Moss rule. The nonlinear susceptibility and the nonlinear refractive index (n₂) decreased with Sb content. The changes in both linear and nonlinear parameters by varying the antimony doping concentration could be helpful for controlling the optical properties of Sb_xSn_1-xS thin films and could be a suitable candidate for many photonics and optoelectronic applications.     

Interpreting the optical properties of oxide glasses with machine learning and Shapely additive explanations

Due to their excellent optical properties, glasses are used for various applications ranging from smartphone screens to telescopes. Developing compositions with tailored Abbe number (V_d) and refractive index at 587.6 nm (n_d), two crucial optical properties, is a major challenge. To this extent, machine learning (ML) approaches have been successfully used to develop composition–property models. However, these models are essentially black boxes in nature and suffer from the lack of interpretability. In this paper, we demonstrate the use of ML models to predict the composition-dependent variations of V_d and n_d. Further, using Shapely additive explanations (SHAP), we interpret the ML models to identify the contribution of each of the input components toward target prediction. We observe that glass formers such as SiO₂, B₂O₃, and P₂O₅ and intermediates such as TiO₂, PbO, and Bi₂O₃ play a significant role in controlling the optical properties. Interestingly, components contributing toward increasing the n_d are found to decrease the V_d and vice versa. Finally, we develop the Abbe diagram, using the ML models, allowing accelerated discovery of new glasses for optical properties beyond the experimental pareto front. Overall, employing explainable ML, we predict and interpret the compositional control on the optical properties of oxide glasses.     

Preparation and refractive index characterization of chalcogenide glasses with gradient refractive index

Infrared gradient refractive index (GRIN) lenses have great application value and potential in multispectral imaging systems. This study reports various chalcogenide axial GRIN glasses prepared using the hot-pressing diffusion method. It is worth noting that the S4–S60 GRIN sample has a difference in refractive index (RI) Δn of greater than 0.3 and a diffusion depth of about 5 mm, which is the deepest diffusion depth reported in chalcogenide glass to date. In addition, the linear portion in the profile of the GRIN sample has a RI difference of 0.15 and a thickness of 1.2 mm. The effects of the temperature, concentration difference, and diffusion time on the sample diffusion process are discussed. The dispersion properties of the GRIN samples were further calculated, providing a new option for correcting chromatic aberrations in optical systems. In addition, a method for the indirect nondestructive characterization of sample RI using the Raman intensity ratio is proposed, and the reliability of the method is verified by practical experiments, which is convenient for the subsequent measurement of the GRIN profile.     

Structure and physical properties of Ge15Sb20Se65‐xSx glasses

We explored the structure and physical properties of Ge₁₅Sb₂₀Se_65‐xS_x (with x = 0, 16.25, 32.5, 48.75, and 65) glasses in order to screen the best compositions for the applications in photonics, since the laser damage thresholds in Se‐based glasses are too low although their optical nonlinearities are high. We found that, linear and nonlinear refractive index of the glasses decreased, but glass transition temperature T_g, optical bandgap E_g and the laser damage threshold increased with increasing S content. We further employed Raman scattering and high‐resolution X‐ray photoelectron spectra to probe the structure of the glasses. Through the analysis of the evolution of the different structural units in the glasses, it was concluded that, the heteropolar bonds (Ge–Se/S, Sb–Se/S) were dominated in these glasses. With the increase in chalcogen Se/S ratio, the number of the Se‐related chemical bonds (Ge–Se, Sb–Se and Se–Se) increased and that of S‐related chemical bond (Ge–S, Sb–S and S–S) decreased gradually, and Ge was prior to bond with S rather than Se. The elemental substitution thus had negligible effect on the glass structure. The change of the physical properties was mainly due to the difference of the strength of the chemical bonds between S–Ge(Sb) and Se–Ge(Sb).     

Lignin-based carbon fibers for composite fiber applications

Carbon fibers have been produced for the first time from a commercially available kraft lignin, without any chemical modification, by thermal spinning followed by carbonization. A fusible lignin with excellent spinnability to form a fine filament was produced with a thermal pretreatment under vacuum. Blending the lignin with poly(ethylene oxide) (PEO) further facilitated fiber spinning, but at PEO levels greater than 5%, the blends could not be stabilized without the individual fibers fusing together. Carbon fibers produced had an over-all yield of 45%. The tensile strength and modulus increased with decreasing fiber diameter, and are comparable to those of much smaller diameter carbon fibers produced from phenolated exploded lignins. In view of the mechanical properties, tensile 400–550 MPa and modulus 30–60 GPa, kraft lignin should be further investigated as a precursor for general grade carbon fibers.     

Infrared GRIN GeS2–Sb2S3–CsCl chalcogenide glass–ceramics

Chalcogenide glasses show a unique potential for creating gradient refractive index (GRIN) lenses, which would reduce the size and weight of infrared thermal imaging system and remain/improve its performance. Here, we propose a new method that forms a GRIN chalcogenide glass–ceramics (GCs) by creating low refractive index (n) CsCl nanocrystals within a high n GeS₂–Sb₂S₃ glass matrix. After specific gradient thermal treatment, the GRIN structure of Δn ∼ 0.04 was formed through the gradient precipitation of CsCl. This work would pave a new path to design the GRIN chalcogenide GCs through a selective crystallization of halide crystals with low n.     

High Brightness 2.2–12 μm Mid‐Infrared Supercontinuum Generation in a Nontoxic Chalcogenide Step‐Index Fiber

An environment friendly nonlinear chalcogenide glass fiber with a Ge‐Sb‐Se core and a Ge‐Se cladding is fabricated for bright broadband mid‐infrared (MIR) supercontinuum (SC) generation. The fabricated Ge‐Sb‐Se/Ge‐Se fiber with a core diameter of 6 μm shows zero group velocity dispersion at ~4.2 μm and ~7.3 μm. By pumping the fiber with a length of 11 cm at 4.485 μm with 330 fs pulses, we achieve a SC covering the 2.2–12 μm spectral range and with an output average power of ~17 mW. This bright broadband SC source is promising for high‐resolution MIR spectroscopy.     

单模塑料光导纤维

综述了单模塑料光导纤维的制作原理及现有的制作技术 ,讨论了各种类型单模塑料光导纤维在传感、通讯、光信息处理等方面的应用     

Preparation of heat‐resistant gradient‐index polymer optical fiber rods based on poly(N‐isopropylmaleimide‐co‐methyl methacrylate)

Using the interfacial gel polymerization method, a heat‐resistant gradient‐index polymer optical fiber (GI POF) was developed based on the copolymer of methyl methacrylate (MMA) and N‐isopropylmaleimide (IPMI) as the matrix material and bromobenzene (BB) as dopant. The gradient distribution of IPMI in the GI POF rod was determined by element analysis. IPMI had great advantage in improving glass transition temperature (T_g) and forming a gradient‐index profile. There was a significant enhancement in the heat‐resistant property in comparison with a conventional GI POF rod. The combination of high thermal stability and easy fabrication makes the novel BB–IPMI–MMA system very suitable for heat‐resistant GI POF. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 280–283, 2003     

Compositional dependence of the optical properties of novel Ga–Sb–S–XI (XI = PbI2, CsI,AgI) infrared chalcogenide glasses

A novel family of Ga₂S₃–Sb₂S₃–XI (XI = PbI₂, CsI, AgI) was investigated to understand the role of metal halides and exploit new chalco‐halide glasses for infrared optics. The dependence of the thermal properties, infrared optical properties, and structural information of the novel family on different metal–iodines was investigated. Results showed that metal halides increase the glass stability but decrease the glass network connectivity. The compositional dependence of the short‐wave cut‐off edge is associated with the electronegativity difference between the cations and anions of the metal halides. Raman study showed that the metal–iodine modified the glass structure mainly through the iodide content, and the cations dissolved in the glass network mostly as charge compensators for the aperiodic network. For the glasses in the series Ga₂S₃–Sb₂S₃–XI–Dy³⁺, Dy³⁺ emission increased in the PbI₂‐ and CsI‐doped glasses but decreased in the AgI‐doped glass due to the combined effect of dysprosium and oxygen. For all that, these novel glasses are highly promised for use in infrared optics.     

Determination of refractive index profile of partially and highly oriented fibers using double refracting interference microscopy

Double refracting polarizing interference microscope designed by Pluta is used with a suggested method to determine the refractive index profile and birefringence profile of partially and highly oriented fibers. The application of this method depends on using Pluta polarizing interference microscope in two positions (crossed position for the duplicated images and subtractive position for the nonduplicated image of the fiber). The mathematical representation of the suggested method is given. The refraction of the light beam inside the fibers is taken into consideration while measuring the fringe shift profile. The refractive index profiles of polypropylene fiber with draw ratio 3.5 are determined using the conventional method. The results are compared with those obtained with the suggested method and found to be in good agreement. The suggested method is applied to determine the refractive index profile of poly(aryl ether ether ketone) partially oriented fiber and poly(ethylene terephthalate) highly oriented fiber. The diffraction of He–Ne laser beam is used to determine the average diameters of these fibers. Microinterferograms are given for illustration. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2341–2347, 2003     

Optothermal properties of fibers. IX. Study changes of optical parameters by multiple-beam technique due to thermal annealing for natural silk fibers

Multiple-beam Fizeau fringes were used for studying the effect of the annealing process on the refractive indices and birefringence of natural silk fibers (best yellow Italian silk, Ford & Co. Ltd). Silk fibers were annealed at a constant time of 2 h with different annealing temperatures ranging from 60 to 160 ± 1°C. A scanning electron microscope was used for measuring the cross-sectional shape and a longitudinal view of the natural silk fibers. The Becke-line method was used for measuring the skin refractive indices and the birefringence of the natural silk fibers. The thermal coefficient of the refractive index, Cauchy dispersion constants, dispersive power, dielectric constant at infinity, polarizability per unit volume, isotropic polarizability, and isotropic refractive index were determined interferometrically. Microinterferograms and curves are given for illustration. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1495–1504, 1998     

Role of Bismuth incorporation on the structural and optical properties in BixIn35-xSe65 thin films for photonic applications

The present paper investigated the influence of Bi concentration on the structural, linear, and non-linear optical properties of thermally evaporated Bi_xIn_35-xSe₆₅ (x = 0, 5, 7, 10, 15 at %) thin films. The structural analysis by the XRD measurements showed the crystalline nature at 7 and 15% Bi while the other concentrations showed amorphous nature. The corresponding bonding change was analyzed by Raman spectroscopy. The optical study by UV-Vis spectroscopy showed the decrease in transmittance and an increase in absorbance property. The linear optical parameters such as absorption coefficient, extinction coefficient, optical density increased while skin depth decreased with Bi additives. The direct, as well as the indirect optical bandgap, decreased along with the decrease in the Tauc parameter. The variation is well explained on the basis of density of defect states by the Mott and Davis model. The non-linear refractive index and non-linear susceptibility increased significantly with Bi % which is good for non-linear optical applications. The static linear refractive index as calculated by the Dimirov and Sakha empirical relation showed an incremental behavior with Bi% concentration and satisfied Moss's rule. The surface structure and elemental concentration were analyzed by FESEM and EDX analysis. The result of the above investigation suggests that these materials can be used as an absorbing layer for several optoelectronic and photonic applications.