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Enhancement of nonlinear optical and thermal properties of polyurethanes by modifying the chromophores with fused heterocyclic and pyrimidine rings
摘要： This article describes the synthesis of substituted triazolo[3,4-b]-thiadiazole heterocycles based nonlinear optical (NLO) responsive chromophores. To enhance the NLO properties of the chromophores, the pyrimidine ring was introduced with an appropriate π-bonding. With these chromophores, different series of polyurethanes were prepared by condensation with tolylene-2,4-diisocyanate and 3,30-dimethoxy-4,40-biphenylene diisocyanate. The structure of the resulting chromophores and polyurethanes was confirmed using Fourier transform infrared, proton nuclear magnetic resonance, and Carbon Hydrogen Nitrogen (CHN) analyzer. The inherent viscosities (ηinh) of the polyurethanes measured by Ubbelohde viscometer were in the range of 0.2324–0.2760 dl/g. Thermal behavior of the polyurethanes was investigated using differential scanning calorimetry and thermogravimetric analysis. The molecular orientation in polyurethane films was induced by a corona poling, and this was ascertained using ultraviolet-visible spectrophotometer and atomic force microscope. The thicknesses and refractive indices of thin films were determined by an Ellipsometer. Polyurethanes exhibited excellent solubility in most of the common organic solvents. The second harmonic generation (SHG) coefficients (d33) of the poled polyurethanes ranged from 63.20 and 95.32 pm/V at 532 nm. None of the polyurethanes showed SHG decay below 100°C, and retained 95% of the signal even up to 500 h. The resulting enhanced NLO efficiency and longer temporal stability make these polyurethanes as promising candidates for photonic devices.
关键词： Polyurethanes,Second harmonic generation,Chromophores,Thermal stability,Nonlinear optical materials
更新于2025-09-23 15:19:57
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Photonic and Electronic Properties of Fluoride Materials || Frequency-Doubling Oxide Fluorides, Borate Fluorides, and?Fluorooxoborates
摘要： The frequency-doubling (FD) materials that are able to expand the frequency ranges of lasers by second harmonic generation (SHG) are the core of the solid-state lasers. FD is a nonlinear optical (NLO) process, in which two input laser beams with the same frequency interacting with an FD material “combine” together to generate a new output laser with twice the frequency and half the wavelength of the initial light beams. This phenomenon was first demonstrated by Franken et al. in 1961. They irradiated a quartz sample using a laser beam with a wavelength of 694 nm, and observed the output light at 347.2 nm. FD is only allowed with coherent light and in mediums without inversion symmetry.
关键词： Nonlinear Optical Materials,Borate Fluorides,Second Harmonic Generation,Frequency-doubling,Fluorooxoborates
更新于2025-09-23 15:19:57
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Spectroscopic ellipsometry and morphological characterizations of nanocrystalline Hg1-xMnxO oxide diluted magnetic semiconductor thin films
摘要： The structural, optical spectroscopic ellipsometry and morphological properties of nanocrystalline Hg1-xMnxO (0 ≤ x ≤ 0.2) oxide diluted magnetic semiconductor thin films synthesized by electron beam deposition technique have been investigated by means of X-ray diffraction (XRD), spectroscopic ellipsometry (SE) and atomic force microscopy (AFM) techniques. All the deposited films crystallize in the form of a hexagonal crystal structure. The integration between X-ray and atomic force microscopy data shows a very good agreement for the nanosize nature of the deposited films. For the surface roughness, good matching between the results of SE and AFM measurements was observed. In the spectral range 200–1200 nm, the real part (ε1) and imaginary part (ε2) of the dielectric constant of nanocrystalline Hg1-xMnxO films have been extracted from SE measurements. At fixed energy value, the ε1, consequently the refractive index is found to decrease with increasing Mn2+ dopant. In contrary, the energy gap (Eg) of the deposited films determined from the ε2 is found to increase as the Mn2+ concentration increases. The variation of both the ε1 and Eg as a function of Mn2+ concentration is understood based on Lorentz-Lorenz relation and sp-d exchange interaction, respectively. The results reported here show that Mn-doped HgO nanocrystalline films could be employed in the fabrication of nanoscale optical and magneto-optical devices.
关键词： Atomic force microscope,Vapor deposition,Spectroscopic ellipsometry,Optical properties,Semiconductors,AFM,Optical materials,Nanostructured materials,Thin films,X-ray diffraction
更新于2025-09-19 17:15:36
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Rewritable Optical Patterns in Light Responsive Ultra High Molecular Weight Polyethylene
摘要： Spiropyran is used as a photochromic dye to create colored patterns in highly drawn ultra high molecular weight polyethylene (UHMW PE) films. The dye is incorporated in highly crystalline, drawn UHMW PE tapes and fibers and isomerizes to its merocyanine state upon UV light irradiation, resulting in a color change from transparent to purple. The isomerization from merocyanine to spiropyran to erase the color can be simply induced using heat or a green LED light. The combination of the use of a mask and the reversibility of the isomerization results in colored patterns which can be written, erased and re-written using UV light and heat or green LED light.
关键词： Polymer fibers,ultra high molecular weight polyethylene,photochromism,light responsive materials,rewritable optical materials,spiropyran
更新于2025-09-19 17:15:36
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Cation-tuned synthesis of the A <sub/>2</sub> SO <sub/>4</sub> ·SbF <sub/>3</sub> (A = Na <sup>+</sup> , NH <sub/>4</sub><sup>+</sup> , K <sup>+</sup> , Rb <sup>+</sup> ) family with nonlinear optical properties
摘要： Four antimony fluoride sulfates named A2SO4·SbF3 (A = Na+, NH4+, K+, Rb+) have been successfully synthesized using a hydrothermal method by introducing Sb3+ cations with a stereochemically active lone pair in sulfates and subsequently tuning the structure through the second monovalent cations. All of the title compounds are stoichiometrically equivalent materials which share a common structural motif composed of a distorted SO4 tetrahedron and an asymmetric SbF3 polyhedron. However, the macroscopic centricities of these four compounds are significantly influenced by the size and coordination environment of cations; Na2SO4·SbF3 crystallizes in centrosymmetric space groups Cmca and (NH4)2SO4·SbF3 in Pbca, while K2SO4·SbF3 and Rb2SO4·SbF3 crystallizes in noncentrosymmetric space group P212121. Complete characterization including thermal analyses, infrared and UV-vis spectroscopy, and theoretical calculations is also reported. Powder second harmonic generation measurement for noncentrosymmetric K2SO4·SbF3 and Rb2SO4·SbF3 indicated that both of them are type I phase-matchable.
关键词： hydrothermal synthesis,cation tuning,nonlinear optical materials,antimony fluoride sulfates,second harmonic generation
更新于2025-09-19 17:15:36
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Printed Soft Optical Waveguides of PLA Copolymers for Guiding Light into Tissue
摘要： The application of optical technologies in treating pathologies and monitoring disease states requires the development of soft, minimal invasive and implantable devices to deliver light to tissues inside the body. Here we present soft and degradable optical waveguides from poly(D,L-lactide) and derived copolymers fabricated by extrusion printing in desired dimensions and shapes. The obtained optical waveguides propagate VIS to NIR light in air and in tissue at penetration depths of tens of centimeters. Besides, the printed waveguides have elastomeric properties at body temperature and show softness and flexibility in the range relevant for implantable devices in soft organs. Printed waveguides were able to guide light across 8 cm tissue and activate photocleavage chemical reactions in a photoresponsive hydrogel (in vitro). The simplicity and flexibility of the fiber processing method, and the optical and mechanical performance of the obtained waveguides exemplify how rational study of medically approved biomaterials can lead to useful inks for printing cost-effective and flexible optical components for potential use in medical contexts.
关键词： soft optical waveguides,printed PLA,printed Resomer?,light guidance,photoactivation in tissues,polymeric optical waveguides,printed optical materials
更新于2025-09-19 17:13:59
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ZnS Nanospheres for Optical Modulator in an Erbiuma??Doped Fiber Laser
摘要： Zinc sulfide (ZnS), which belongs to transition metal monochalcogenides, is a semiconductor material with wide direct band gap. It can potentially show some special applications (such as luminescence, phosphor, sensors, infrared window materials, photocatalysis) by changing the morphology, size, and crystal structure of semiconductor materials. However, ZnS nanospheres have not been studied as optical modulators until now. Herein, ZnS nanospheres are synthesized by the hydrothermal method and are used to realize optical modulators in an Er-doped fiber laser. The evanescent field effect is utilized to incorporate the ZnS nanospheres on a tapered fiber. Furthermore, with the increase in pump power, the modulation interval gradually decreases to a minimum of 34.36 ns corresponding to the modulation frequency of 29.1 MHz, which is the highest modulation frequency to our knowledge in a ring cavity all-fiber laser. These results demonstrate ZnS nanospheres together with the interaction of dispersion and nonlinearity in optical fibers can modulate the proposed lasers. This not only provides a new method for controlling the power and frequency of all optical modulators, but also marks an important step for ZnS materials in optics research and device applications.
关键词： optical modulators,nonlinear optical materials,ring cavity fiber lasers
更新于2025-09-19 17:13:59
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Synthesis and photoluminescence studies of novel double-perovskite phosphors, Ba2GdTaO6:Eu3+ for WLEDs
摘要： A series of novel double-perovskite type red emitting phosphors, Ba2Gd1-xTaO6:xEu3+ were synthesized via solid-state reaction route. Powder X-ray diffraction results confirmed the cubic perovskite phase and scanning electron microscope was used to evaluate the morphology of the phosphors, respectively. Detailed studies on UV-Vis absorption showed that Eu3+ doped Ba2GdTaO6 phosphors have obvious absorption in the ultraviolet region. The excitation of UV (CTB), near UV (394 nm) and blue light (467 nm) match the output wavelength of ultraviolet and blue LED chips, and red-light emission is observed, which is mainly due to the magnetic dipole (5D0→7F1) and electric dipole transition of (5D0→7F2) of Eu3+. The results show that the energy transfer from Gd3+ to Eu3+ enhances the luminescence. Concentration quenching was observed when Eu3+ doped at more than 10 mol%. Thermal quenching was measured and the activation energy was 0.230 eV. The prepared phosphors have potential applications in WLEDs.
关键词： WLEDs,Optical materials,Photoluminescence,Phosphors
更新于2025-09-19 17:13:59
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Aligning ?±a??alumina platelets via uniaxial pressing of ceramica??filled polymer blends for improved sintered transparency
摘要： Uniaxial warm pressing was used to align alumina platelet-filled polyethylene-based copolymer blends. The solids loading (30-40 vol.%) and platelet diameter (1.2 and 11 μm) were varied to compare effects on viscosity, percent reduction, and final alignment. All ceramic-filled thermoplastic polymer blends exhibited pseudoplastic behavior. Crystallographic alignment of green body samples was quantified by the orientation parameter (r) and grain misalignment angle (full width at half maximum, FWHM) obtained from rocking curve analysis. Blends with 11 μm diameter platelets displayed a higher temperature sensitivity constant, better flow properties, and higher alignment compared to blends with 1.2 μm diameter platelets. Optimal samples produced with blends containing 30 vol.% of 11 μm diameter platelets demonstrated an alignment of r = .251 ± .017; FWHM = 11.16° ± 1.16°. A sample with optimal alignment was hot-pressed to transparency and obtained an in-line transmission of 70.0% at 645 nm. The final alignment of this pre-aligned hot-pressed sample (r = .254 ± .008; FWHM = 11.38° ± 0.54°) improved when compared to a non-pre-aligned sample (r = .283 ± .005; FWHM = 13.40° ± 0.38°).
关键词： hot pressing,rheology/rheometry,alumina,optical materials/properties
更新于2025-09-19 17:13:59
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Influence of H2 Atmosphere Annealing on Plasmonic Properties of Cu-Containing Silica Films Sputtered on Amorphous Silica
摘要： Copper-doped silica films have been deposited on amorphous silica (fused quartz) by magnetron co-sputtering. The resulting films were characterized for copper loading/thickness by Rutherford backscattering spectrometry, and the optical properties were evaluated by absorption and photoluminescence spectroscopies. The films were subjected to thermal treatment under a 5% H2?95% Ar-reducing atmosphere and further evaluated for surface plasmon resonance (SPR) characteristics. In addition, the occurrence of Cu nanoparticles (NPs) was evaluated by transmission electron microscopy. It is indicated that the films have effective permeability for H2, and consequently, the reduction of ionic copper takes place supporting the nucleation and growth of Cu NPs. Interestingly, along with the increase in absorption intensity of Cu NPs, the processing leads consistently to significant blue shifts in the SPR peaks. Absorption spectra were then simulated by Mie theory calculations for dielectric-embedded Cu NPs in an effort to understand the influence of particle size and medium refractive index on the SPR.
关键词： Thin films,Surface plasmon resonance,Optical materials
更新于2025-09-19 17:13:59