Optical Materials: X最新文献

A semi-empirical method is introduced to estimate the emission energy of the Mn⁴⁺ ion in fluorides and oxides without using spectroscopic data as inputs. The method is based on the calculation of the nephelauxetic function he at the octahedral crystal sites occupied by the Mn⁴⁺ cations in the considered host lattices. Only structural data are required for this calculation. The model reproduces the experimental emission energy of Mn⁴⁺ in 51 tested fluorides and 101 tested oxides within ±300 cm⁻¹ in 98% of the fluorides and within ±500 cm⁻¹ in 85% of the oxides. The accuracy is lowered as the he value, i. e. the covalency of the Mn–O bonding, is raised.

Academic studies of imperfections in insulating crystals and glasses initially assumed the sites were simple and isolated. In part this was the result of the original simplistic characterisation and modelling. Unfortunately many textbooks, teaching and publications engrained this viewpoint. More detailed techniques invariably showed those ideas to be incorrect, with numerous examples of extremely long range interactions, multi-sites packages, and even phase separations or nanoparticle inclusions. Despite these examples, current defect models still often focus on extremely localised sites. This seems particularly inappropriate, as in many modern applications the materials are heavily doped, and in a powder format. It therefore seems essential to include, or reintroduce, analysis techniques which can reveal both the long range effects, and the variations that exist as a function of powder size and method of production. Where such data exist, they reveal considerable complexity. This overview thus comments on past and future analysis techniques with the sensitivity to enhance detailed models. Site models require, and will benefit from, a wider acceptance of medium and long range interactions. Realistically, many sites exist simultaneously, so models will never be perfect, but improved characterisation can assist not only the science, but also commercial developments. Inevitably there are self citations as we have actively exploited a range of techniques that can reveal evidence of long range defect production and sensitivity to extended lattice perturbations.

Cerium doped (Lu,Y)₂SiO₅ (or LYSO) single crystals have been studied by means of luminescence excitation spectroscopy in the temperature range from 7 up to 300 K. Vacuum ultraviolet excitations in 4.5–8 eV energy range from synchrotron radiation of 1.5 GeV storage ring of MAX IV synchrotron facility. It is shown that both type of Ce³⁺ emission centers (seven and six coordinated centers) are excited under any excitation energy used. It was concluded that the same energy transfer processes from host lattice to impurity ions are involved independently on coordination of Ce³⁺. It is also demonstrated that excitonic mechanism of energy transfer is dominant under chosen excitation and intrinsic and bound excitons are included in excitation of Ce³⁺ luminescence in LYSO.

Doxorubicin (DOX) interaction with 2D boron nitride (BN) nanoparticles was studied experimentally and theoretically. The BN nanoparticles, namely nanoflakes, were obtained by direct liquid-phase exfoliation via preliminary stratification in a planetary ball mill from massive hexagonal BN. 2D BN nanoparticles and DOX/BN composites were characterized using visible steady-state, time-resolved fluorescence, FTIR and Raman spectroscopy, Coherent Anti-Stokes Raman Scattering (CARS) microscopy and density functional theory (DFT). The BN nanoflakes from 2 to 3 layers up to hundred nm in lateral direction possessed crystalline properties that formed the DOX/BN composites with fluorescence in the range of 520–750 nm that can be used in DOX detecting. The calculations revealed a notable electron transfer between the BN monolayer and the DOX molecule, which, however, is partly offset by the redistribution of charge within the monolayer. The energy of interaction of the BN with DOX was estimated as 1.96 eV, indicating that the DOX/BN composite formation is an exothermic process. The Fluorescence quenching of DOX/BN occurs with increased BN nanoparticle concentration. The optimal concentration for composite formation was chosen. In CARS imaging of the Lewis lung carcinoma cells after treatment with DOX/BN, brightly luminous points are observed inside the cells, indicating the accumulation of DOX/BN composites that can be used in bioimaging and theranostics.

The integration of highly transparent and highly conductive layers plays a crucial role in the advancement of various next-generation optoelectronic technologies. Here, we demonstrate a comparison of optical, electrical and wettability properties of Aluminum-doped Zinc Oxide (AZO) deposited by Atomic Layer Deposition Technique (ALD) with commercially available Fluorine-doped Tin Oxide (FTO) and Indium-doped Tin Oxide (ITO) Transparent Conductive Oxide (TCO) layers. Their impact on the electro-optical modulation behavior when applied in Liquid Crystal (LC) device assemblies are compared and discussed. The AZO layers performance prove that are fully competitive to the commercial FTO and ITO layers and verify the high demand for the next generation indium tin oxide (ITO)-free technology.

We investigate co-doped ZnSe: (Cr, Fe) laser crystals with an approach that includes both optical spectroscopy and theoretical modelling. We found that concentrations of chromium and iron up to 10¹⁸ cm⁻³ are optimal for obtaining a homogeneous solid solution in designing laser crystals. Higher dopant concentrations lead to the formation of clusters with spinel structure in the ZnSe matrix. The optimal effectiveness of ZnSe laser media with active Cr²⁺ and Fe²⁺ elements is achieved at temperatures of around 100 K. Heating induces charge transfers like Fe²⁺→Fe³⁺ and Cr²⁺→Cr³⁺, while cooling results in phonon freezing. A theoretical model has been developed to explain the observed temperature evolution of the absorption spectrum. The types and values of distortions of the Cr- and Fe-based coordination complexes are determined. We have found that the Jahn-Teller distortions are crucial for modelling the temperature-dependent changes of the absorption spectra.

Pr-doped scintillators are attracting attention because of their potential applications in medical devices. In this study, we focused on Pr-doped (La, Y)₂Si₂O₇ scintillators to grow single crystals by the micro-pulling-down method and to evaluate their optical and scintillation properties. From the powder XRD results, the crystal structure and the space group were identified to be monoclinic and P2₁/n, respectively. The results of optical and scintillation characterization show that the luminescence from the Pr³⁺ 5d₁–4f transition increases with increasing Pr³⁺ concentration. The maximum light yield was also obtained for the sample with the highest Pr³⁺ concentration. The Pr-doped (La, Y)₂Si₂O₇ single crystal shows promising properties for application in radiation detection.

The essential properties of BaGa₄S₇ (BGS), BaGa₄Se₇ (BGSe), BaGa₂GeS₆ (BGGS), BaGa₂GeSе₆ (BGGSe), and Ba₂Ga₈GeS₁₆ (B2GGS) are reviewed, together with all nonlinear optical applications of these non-centrosymmetric crystals realized so far.

This paper aims to investigate theoretically addition of the Dy³⁺ content on the optical and radiation attenuation properties of TeO₂–ZnO – Na₂O–Sm₂O₃ glasses. The STZNDy1 possesses the greatest molar refractivity (R_m) and molar polarizability (α_m) whereas the STZNDy5 possesses the lowest R_m and α_m. When Dy₂O₃ content adds into the glass, the reflection loss sharply increases then it declines up to 1.5 mol.% of Dy₂O₃ content afterwards it is stable however the optical transmission sharply decreases then it increases up to 1.5 mol % of Dy₂O₃ content afterwards it is stable. The STZNDy5 and STZNDy6 own the greatest metallization criterion while they own the lowest static dielectric constant and optical dielectric constant. Both linear attenuation coefficient and mass attenuation coefficient of the STZNDy glasses increase with the addition of the Dy₂O₃ content. The STZNDy1 has the highest half value layers (HVLs) and tenth value layers (TVLs) whereas the STZNDy6 has the smallest HVLs and TVLs. The radiation protection efficiency enhances whereas mean free path declines as Dy₂O₃ content increases in the glasses. Consequently, the STZNDy6 owns the good radiation attenuation ability in the STZNDy glasses, and adding Dy₂O₃ increases the radiation attenuation characteristics of the STZNDy glasses.

In this work we present the design, fabrication and study of the optical properties of hyperbolic materials based on multilayered metal–dielectric Ru/TiO${}_2$ structures. The samples were fabricated using the Atomic Layer Deposition technique, and their structure was designed to have an Epsilon Near Zero point near 800 nm to match the laser wavelength employed to study their response. The linear optical properties were studied using spectrophotometry and spectral ellipsometry. The nonlinear response was studied as a function of incident irradiance using the z-scan technique with fs pulses as a function of wavelength throughout the visible, allowing the determination of the refractive and absorptive contributions to the nonlinear response. Given that a high pulse repetition rate was employed, cumulative pulse to pulse thermal effects can be present, because of this, a modification of the z-scan technique allowed the resolution of the electronic and thermal contributions to the response.