Narrow Results

The classic melt-quench method was used to make unique transparent cadmium sodium bismuth borate glasses with a composition of $x\cdot \mathrm{\text{CdO}}$ (18$-x)$ Na₂$\mathrm{\text{O}}\cdot 18$Bi₂O${}_3\cdot 64$B₂O₃; for ($x=0$, 6, 8, 10, 12). Different analytical equipment such as XRD, UV-Vis-NIR, Raman, DSC, and FTIR were employed to characterize and analyze the manufactured glass samples. The density and oxygen packing density of produced glass samples increased linearly with CdO addition, whereas the molar volume decreased. The X-ray diffraction method was employed to anticipate the amorphous nature of the prepared glass samples. The structural alterations of the generated glasses were investigated using FTIR and RAMAN spectra. DSC was employed to assess the thermal characteristics related to the crystallization temperature ($T_p)$ and glass transition temperature ($T_g)$. DSC demonstrates the result that CdO content contributes most to enhancing the thermal stability of glasses. The ($T_g)$ values increased while ($T_p)$ values decreased as CdO substitution increased. Infrared and Raman spectroscopy were used to conduct a thorough examination of structure, which revealed that these glasses were comprised of both symmetric and asymmetric stretched vibrations of bonds. The absorption spectra in the ultraviolet-visible range of the samples indicated a reduction in the optical bandgap as CdO content increased. All the findings indicate that the CdO level in glass samples acts as a network modulator, while BO₄ does not.

Flexible polymer nanocomposite composed of organic methylcellulose (MC) and semiconducting titanium dioxide (TiO₂) films were successfully prepared. The energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR) recorded the structure characteristics of the films, proving that MC/TiO₂ nanocomposite were successfully synthesized. The EDX showed that this composite was composed of (28.55% C, 50.90% O, and 20.55% Ti), which displayed the chemical composition of MC/TiO₂. Moreover, the scanning electron microscope (SEM) shows the TiO₂ nanoparticles are loaded homogenously in the nanocomposite films. With increasing the TiO₂, the FTIR intensity of most peaks gradually decreased which may be attributed to that titanium dioxide nanoparticles (TiO₂ NPs) were formed on the methylcellulose (MC). The UV spectrophotometer records the data of absorption (A) for the MC and MC/TiO₂ films between 200nm and 1100nm at the ambient temperature. Using Tauc’s relation, the linear/nonlinear optical characteristics of MC and MC/TiO₂ films were computed. By mixing MC with 2%, 4%, and 6% TiO₂, the Urbach energy of the MC is enhanced from 1.77eV to 1.85, 2.02, and 2.34eV, correspondingly, while the TiO₂ reduced the energy gap of MC from 5.17eV to 3.59, 3.52, or 3.43eV. Moreover, the carbon cluster increased from 44 for MC to 92, 95, and 101 for MC mixed by 2%, 4%, and 6% TiO₂. This study found the MC/TiO₂ hybrid films can potentially be used as optical materials for flexible electronic devices.

This study employs the FP-LAPW method based on DFT to investigate the structural, electronic, and optical properties of Cs₂SnBr₆ and Cs₂SnCl₆ under a range of pressures up to 30GPa. We use the TB-mBJ functional to analyze the electronic and optical properties of the materials, while the GGA–PBEsol is employed to study their structural properties. Applying pressure causes a decrease in the unit cell volume and lattice constant of the double perovskites. At zero pressure, both Cs₂SnBr₆ and Cs₂SnCl₆ exhibit a direct bandgap. The bandgaps of both the materials decrease as the pressure increases from 0GPa to 20GPa but slightly increase for the increase in pressure from 20GPa to 30GPa. The DOS analysis conducted at 0GPa and 30GPa demonstrates a decrease in the number of states pereV as the pressure increases, along with an increase in bandwidth and a shift of the peaks toward negative energy. The electron density contours exhibit the presence of both covalent and ionic bonds at zero pressure, whereas at a pressure of 30GPa, the covalent bond strength is enhanced. Optical properties of Cs₂SnBr₆ and Cs₂SnCl₆ were investigated over a pressure range of 0–30GPa and a photon energy range of 0–10eV. With increasing pressure, the initial peak in these parameters was red-shifted due to a decrease in bandgap energy, while the remaining peaks blue-shifted due to the broadening of conduction and valence bands.

In this work, the mesomorphic, morphologic, thermotropic, thermooptical, and thermodynamical properties of 4-(octyloxy)-N-(4-hexylphenyl)-2-hydroxybenzalimine thermotropic liquid crystalline compound, which was synthesized by our group, have been studied in detail. This compound displays smectic C and nematic mesophases. These mesophases are enantiotropic and exhibit specific confocal and schlieren textures, respectively.

Thermotropic, thermooptical, and thermodynamical properties of the compound at direct and reverse phase transitions between smectic C and nematic mesophases and also between nematic mesophase and isotropic liquid have been investigated. The peculiarities of the bistable heterophase regions of these phase transitions have been studied.

Structural, electronic, magnetic and mechanical properties of the perovskites BiFeO₃ (BFO) and BaTiO₃ (BTO) are investigated using density functional theory (DFT). Structural and mechanical parameters are calculated using generalized gradient approximation (GGA) and the results consistent with the available literature. The stable magnetic phases are achieved by optimizing total energies versus volumes of the cells in different magnetic configurations such as nonmagnetic (NM), ferromagnetic (FM) and antiferromagnetic (AFM). BTO is found to be NM while BFO favors G-type AFM (G-AFM) phase. The electronic properties are investigated using GGA, GGA with Hubbard potential (GGA+U) and modified Becke–Johnson (GGA-mBJ) exchange–correlation functionals. BFO is found to be a direct bandgap semiconductor having gap energy value 3.0 eV whereas BTO is an indirect semiconductor with bandgap energy 2.9 eV. Spin–orbit coupling effect is dominant in BFO due to the larger size of A-site cation. The electrical polarization shows that both the compounds are ferroelectric materials with significant spontaneous polarization of 144.1 $\mu$C/cm² and 27.9 $\mu$C/cm² for BFO and BTO respectively.

Bismuth-based glasses containing ZnO, B₂O₃ and Li₂O are investigated through different physical, polarizability and transport properties. Raman spectroscopy reveals that these glasses are built from [BiO₃] and [BiO₆] units. Zinc in tetrahedral form is also observed. Density and glass transition temperature increase with the bismuth content. The refractive index, oxide ion polarizability and optical basicity also increase with the Bi₂O₃ content, whereas the interaction parameter decreases. The DC electrical conductivity increases and the activation energy decreases with the increase in the Li₂O content.

A series of Hf, Er co-doped LiNbO₃ crystals were grown by Czochralski technique with 1 mol% of Er₂O₃ and with 2, 4, 6 and 8 mol% of HfO₂, respectively. The optical damage resistance of Hf:Er:LiNbO₃ crystals was studied by the transmitted beam pattern distortion method. The optical damage resistance of Hf (6 mol%): Er:LiNbO₃ crystals is about two orders of magnitude higher than that in Hf:Er:LiNbO₃. The X-ray power diffraction, the ultraviolet-visible absorption spectra and the infrared absorption spectrum were measured and discussed in terms of the spectrometric characterization and the defect structure of crystals. The results showed that with mild co-doping with HfO₂, Er³⁺ substitutes Nb⁵⁺, whereas with heavy co-doping, a part of Er³⁺ substitutes Li⁺. The structure defects were discussed in this paper to explain the improvement of the optical damage resistance in the Hf:Er:LiNbO₃.

Dy-Bi co-doped yttrium tungstate crystal materials were synthesized by high temperature solid-state method. To reveal the photoluminescence features and properties of the samples, some measurements have been taken. It turned out that different Bi${}^{3+}$ concentrations play obvious influence in emission performance, and show visible light emission under ultraviolet light excitation. Besides, the effect of temperature on phase structure of samples has also been studied here. Superhigh X-ray luminescence of the phosphors exhibited the promising application in the field of high energy detection. The X-ray irradiation crystal resistance stability of the phosphors has also been investigated through the subsequent testing of XRD and spectra.

We present a theory on stratified nonlinear magneto-photonic crystals, with arbitrary spatial distribution of the refractive index and magneto-optical coefficients. The coupled mode theory is formulated for plane waves inside the crystal, and a perturbation series of integral solutions for the spectral response of the crystal is presented. Material issues and configurations are discussed, and the described theory is applied to the calculation of transmission spectra of binary magneto-photonic crystals.

The crystals N-(2-chlorophenyl)-(1-propanamide) (NCP) appropriate for nonlinear optical (NLO) and electro–optic appliances were grown full-fledged by the slow cooling method. The solubility and metastable zone width range of NCP specimen were studied. The specimen crystallizes in the monoclinic crystal system with noncentrosymmetric space group of P2₁. The crystal morphology study also elucidates supplementary excellence of the as-grown NCP crystal. The optical precision in the whole visible region was found to be superior for NLO claim. The crystallinity of the full-fledged crystal is determined by etching and HRXRD. Laser harm threshold and photoluminescence studies delegate the grown crystal comprises extremely less imperfections. The mechanical deeds of NCP sample at assorted temperatures were examined to decide the hardness solidity of the grown specimen. The piezoelectric behavior and the comparative second harmonic generation for assorted particle sizes of the material were also deliberate. The third-order nonlinear ocular possessions of NCP crystal specimen were determined by Z-scan method. The optical homogeneity of the solitary crystal was assessed using customized channel spectrum technique. The thermal structures of NCP solitary crystal have been studied using photopyroelectric method. The half-wave voltage of the full-fledged crystal was intended from the electro–optic experimentation. Photoconductivity nature of the grown crystal outlined consummate inducing dipoles due to strong incident radiation and further revealed the nonlinear deeds of the grown material.

By using the slow evaporation solution growth technique, the 2-amino 6-methyl pyridinium 4-methyl benzoate (2A6MP4MB) is crystallized in a single, high-quality crystal. Single crystal X-ray diffraction (SXRD) was used to determine the crystal structure. The different functional groups of the substances were identified using Fourier Transform Infrared Spectroscopy (FTIR) analysis. The 2A6MP4MB crystal exhibits a significant optical transmittance throughout the complete visible spectrum and a lowered UV cutoff wavelength, according to studies conducted using UV-Vis spectrometers. The optical band gap energy (Eg) of a single crystal of 2A6MP4MB is 4.768eV. The compound’s photoluminescence (PL) spectrum in the title illustrates the green emission technique. We analyze the produced single crystal’s dielectric tensorial behavior at various frequencies. The produced 2A6MP4MB crystal’s third-order susceptibility, nonlinear refraction, and nonlinear absorption coefficient were evaluated using the $Z$-scan technique. A Vickers hardness tester was used to assess the created crystal’s mechanical stability.

Undoped and Mn (1 and 3 at.%) doped ZnO nanoparticles were synthesized by a simple chemical co-precipitation method. Rietveld refinement of X-ray diffraction (XRD) data revealed that undoped and Mn doped ZnO nanoparticles crystallize in the monophasic wurtzite structure and monotonous expansion of the lattice constants with increasing Mn content, due to the effective Mn doping. TEM images of all the samples showed the monodispersive spherical particles with the size of ~7 nm. The quantum confinement of nanoparticles was tested from UV–Vis absorbance measurement and the particle sizes were calculated and compared with TEM and XRD. The chemical compositions were analyzed by energy dispersive spectroscopy (EDS). In order to investigate the origin of ferromagnetism, the electronic structures of the Zn, O, and Mn atoms were probed by X-ray photoelectron spectroscopy (XPS). XPS data revealed that most of the dopants (Mn) exists in +2 oxidation state for 3 at.% Mn doped ZnO sample. The magnetization curves of the Mn doped ZnO samples indicate the existence of room-temperature ferromagnetic (RTFM) behavior. Here the observed RTFM in Mn doped ZnO can be attributed to the substitutional incorporation of Mn at Zn sites rather than due to the formation of any secondary phases.

Bulk SiO₂-based inorganic–inorganic sonogel (SG) hybrid glasses were fabricated with Ag/SiO₂ supported metal nanoparticles (MNPs). The catalyst-free SG route was implemented to produce these optically active nanostructured composites by doping the liquid sol-phase with Ag/SiO₂ synthesized according to the deposition–precipitation method. As prepared Ag/SiO₂-MNPs exhibited particle diameters below 10 nm and homogeneous size distribution. The easy and homogeneous Ag/SiO₂ loading within the micro/mesoporous SiO₂-SG network has evidenced the guest–host chemical affinity of these systems. This fact allowed us to fabricate outstanding chemically, photo-physically and mechanically stable bulk hybrid monoliths with controllable geometry and doping rates, suitable for linear and nonlinear optical (NLO)–spectroscopic characterizations. Indeed, the hosting SG matrix provided an elevated thermal and mechanical stability protecting the reactive Ag nanoparticles from environment conditions, diminishing their tendency to from aggregates and, above all, preserving their pristine photophysical properties. Comprehensive morphological, structural, spectroscopic and NLO characterizations were performed on the obtained SiO₂:(Ag/SiO₂) hybrid composites. Results have shown that the nanocrystalline (NC) properties, multipolar nature and small sizes of the implemented Ag/SiO₂-nanoparticles, together with the bulk guest–host mechanical interactions, play a crucial role for the observation of outstanding spectroscopic and quadratic NLO properties of the developed hybrid systems.

Polycyclotrimerization and polycoupling of acetylenic monomers respectively furnish hyperbranched polyarylenes and polyynes with high molecular weights (up to 1×10⁶) in high yields (up to 99.9%). The polymers possess low intrinsic viscosities and high thermal stabilities, losing little of their weights when heated to > 400°C. Upon pyrolysis at > 800°C, the polymers graphitize with high char yields (up to 86%). Hyperbranched polyarylenes efficiently emit deep-blue to blue-green lights with fluorescence quantum yields up to 98% and strongly attenuate intense laser pulses with optical power-limiting performances superior to that of C₆₀, a well-known optical limiter. Poly(alkenephenylenes), poly(aroylarylenes) and polyynes are readily cross-linkable by UV irradiation, serving as excellent photoresist materials for the generation of patterns with nanometer resolution. Thin films of hyperbranched polyynes exhibit very high refractive indexes (n up to 1.86). The internal and terminal acetylene moieties of the polyynes readily form complexes with cobalt carbonyls, which can be transformed into soft ferromagnetic ceramics with high magnetic susceptibilities (M_s up to ca.118 emu/g) and near-zero magnetic losses.

The optical and magneto-optical activities of yttrium iron garnet are shown to depend on the sintering stage. Low density yttrium iron garnet presents a lower optical activity than the high density garnet. The magneto-optical activity decreases at energies in which the optical transitions are associated to crystal field, indicating a relationship between the optical activity and the distortion of the structure. Finally, a calculation routine has been given to obtain the different elements of the dielectric tensor in bulk materials.

The low-temperature combustion synthesis (LCS) method is the most popular method for the synthesis of ultrafine oxides and compound oxides. A kind of Er-Y-Pb-Na quaternary fluoride sensitive to 1.55 μm was synthesized by the LCS method and the synthesis conditions were optimized with orthogonal experiments. Intense upconversion emissions at 522 nm, 541.4 nm and 654.7 nm corresponding to the ²H_11/2, ⁴S_3/2 and ⁴F_9/2 transitions to the ⁴I_15/2 ground state were observed when excited by CW laser radiation at 1.55 μm. The effect of the carbamide amount on the phase formation and the luminescence intensity was analyzed. The product is of uniform particle size of ca. 40 nm, which is very outstanding for its reutilization in the infrared detection field.

We report the results of investigation of dielectric spectroscopy study of single crystals of ${\mathrm{Bi}}_{12}{\mathrm{GeO}}_{20}$ and ${\mathrm{Bi}}_{12}{\mathrm{GeO}}_{20}$ doped with Co nanoparticles. The complex dielectric constant was measured in the temperature interval from 5 to 450 K and frequencies from 1 Hz to 1 MHz. The electrical conductivity of both samples was thermally activated with potential barriers of 0.55 eV and 0.59 eV, respectively. Doped samples had bigger complex dielectric constants and $\sigma \prime$ exhibited slightly steeper temperature dependence than in the pure sample. The dielectric relaxation was observed in pure and doped single crystals and relaxation frequencies showed similar activation energies as electrical conductivities.

Glasses having composition 20CdOxBi₂O₃(79.5-x)B₂O₃0.5Pr₆O₁₁ with x varying from 15 to 35 mol% have been synthesized. Optical absorption and fluorescence spectra were measured at ambient temperature. A close correlation is observed between the Bi₂O₃ content and the spectroscopic properties such as Judd-Ofelt intensity parameters Ω_λ = (λ = 2, 4, 6), radiative and structural properties of prepared glasses doped with Pr³⁺ ion. The variation of Ω₂ with Bi₂O₃ content has been attributed to changes in the asymmetry of the ligand field at the rare earth (RE) ion site (due to structural change) and to changes in RE-O covalency, whereas the variation of Ω₆ has been related to the variation in RE-O covalency. Following the luminescence spectra, various radiative properties like transition probability (A_rad), radiative lifetime (τ_r), branching ratio (β_r) and stimulated emission cross section (σ) have been calculated. The branching ratio for ³P₀ → ³F₂ transition of Pr³⁺ glass system arrive at 41 to 40%, respectively, and the predicted spontaneous radiative transition probability rates are high and varies from 14032 to 14864 s⁻¹. In addition, the glass stability is improved in which the substitution of B₂O₃ for Bi₂O₃ strengthens the glass network structure. The bismuth based glass as a host for Pr³⁺ ion doped suggesting their suitability for laser applications.

The main focus of laser cleaning research at Macquarie University, Sydney, Australia, has been developing techniques for cleaning applications in the optics, optoelectronics and photonics industries. Dry/raised humidity cleaning techniques are favoured for small scale optical, integrated-optic and photonic devices. All of wet, damp and dry laser-cleaning methods are applicable to larger scale optics. All of our studies to date have measured the laser cleaning result effected by a single laser pulse. Excellent removal efficiencies of alumina particles (0.3 µm −tens of microns) from glass surfaces have been obtained. Also we have used “dry” particles rather than particles in suspension. Use of dry particles leads to significant agglomeration, thus, our studies evaluate the impact of particle agglomeration on laser cleaning results. In the sections that follow we firstly present some tables summarizing the results from experimental laser cleaning studies, from the research literature published at the time of writing. Then, secondly, we review our own laser cleaning research from the perspectives of development and critical evaluation of the experimental and analysis methods, contrasting laser cleaning results achieved with different UV pulsed laser systems, and accurately measuring laser cleaning threshold fluence.

In this work, the influence of Y³⁺ doping on the phase transformation and photoluminescence properties of Gd₂O₃:Eu³⁺ red phosphor was studied. Red-emission (Gd_0.95-xY_xEu_0.05)₂O₃ phosphor particles have been processed via homogeneous precipitation precursor synthesis followed by calcination at 1300 °C for 4h. The resultant oxides could be modulated from a pure monoclinic phase to a pure cubic phase by Y³⁺ doping. The phosphor with a cubic structure shows a significantly stronger red emission, and a blue shift of the charge-transfer band (CTB) was observed on the excitation curve by Y³⁺ doping. These phenomena have been deciphered by considering structural features of the products.