Glass scintillators have attracted researchers from all over the world because of their property-driven applications and lower cost when compared to commercial crystals. In this study, multi-component fluoride-based contents doped with cerium fluoride glasses were synthesized and studied to determine their potential for scintillating device applications. The samples were exposed to photoluminescence and a high-energy X-ray/gamma-ray beam. The scintillation yield and decay time were measured. Absorption spectra were used to analyze the optical properties, while Raman spectra were used for structural studies. The scintillation yield for 10 mol% CeF3 content glass was 17.16% compared to BGO crystal, indicating their potential role in scintillating device applications.

The coherent spin dynamics of electrons are investigated for CsPbI3 perovskite nanocrystals in a glass matrix using time-resolved Faraday ellipticity. In nanocrystals with a diameter of about 11 nm, the Larmor precession frequency has a linear dependence on the magnetic field corresponding to the electron Land & eacute; g factor of 2.07. We find a finite Larmor precession frequency at zero magnetic field, corresponding to the electron spin splitting of 0.8 mu eV. This splitting is explained by the hyperfine interaction with nuclear spin fluctuations. Our model analysis shows that the hyperfine interaction for the conduction-band electrons is contributed both by the p orbitals of the lead atoms and by the s orbitals of the iodine atoms, with the leading contribution to the hyperfine field fluctuations coming from iodine. This fact agrees well with the 9% iodine contribution to the Bloch amplitude of the conduction band, obtained by density functional theory calculations. From these findings, the atomic hyperfine constant for the 5s orbital of iodine is evaluated as 190 mu eV.

The Landé g -factor of charge carriers is a key parameter in spin physics controlling spin polarization and spin dynamics.

A series of fluorophosphate glasses with CdSe and CdSe+ZnSe were successfully synthesized. After heat treatment above the glass transition temperature, CdSe QDs of 1.5-5.5 nm were formed. Glass-ceramics doped with QDs of 2.0-2.5 nm exhibited trap emission in the 670-690 nm region with a QY of 60%. Increasing the size of quantum dots leads to a sharp decrease in the quantum yield. It was found that the Se/Cd ratio and the introduction of zinc ions does not change the observed broadband luminescence due to the transition from the lower excited state of conductor band to accepter trap states. The PL of CdSe QDs in glass is due to the recombination of a spatially separated electron from the conduction band and a hole on the QDs surface. Increasing the temperature in the range of 10-300 K leads to a linear decrease in PL intensity.

A series of fluorophosphate glasses with CdSe and CdSe+ZnSe are successfully synthesized. After heat treatment above the glass transition temperature, CdSe quantum dots with sizes 1.5-5.5 nm are formed. The luminescence spectra of CdSe quantum dots are analyzed at various temperatures, excitation energies and chemical composition of glass. The influence of selenium content on the growth features of quantum dots is shown. The size dependence of luminescence quantum yield on the QDs size is found. The 2.0-2.5 nm-sized QDs demonstrate trap emission in the region of 1.7-1.85 eV with a maximum quantum yield of 60 %. It is found that only a broad band due to the transition from the low state of the conduction band and the shallow donor trap states to the deep accepter trap levels is observed. This broad emission band is observed at any selenium cadmium ratio and zinc introduction.

To study the influence of the nucleation mechanism in lithium aluminosilicate glass, a composition similar to commercially produced glass was used. The glass-ceramics was obtained as a result of two-stage heat treatment, differing in the nucleation temperature and coinciding in the temperature and time of crystal growth. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were used to study the formed nanocrystals. It was shown that the change of nucleation temperature in the glass transition interval T-g +/- 15 degrees C significantly affects the coefficient of thermal expansion, which is due to the formation of a different number of nanocrystals of the general composition LixAlxSi1-xO2 with x = 0.33 with the size less than 50 nm.

The photoluminescence (PL) spectra of CsPbBr3 perovskite nanocrystals grown in a fluorophosphate glass matrix exhibit phonon replicas of the exciton line. The dependence of intensity of the phonon replica on its number is simulated taking into account the difference in the curvature of the excited and ground adiabatic potentials. The Raman spectra of CsPbBr3 nanocrystals are measured. Calculations based on the density functional theory is performed to obtain the spectrum of phonon states of these crystals in the orthorhombic phase. The phonon frequencies observed in the PL and Raman spectra are compared with the calculation results.

The effect of cadmium ions introduced into fluorophosphate glass on the growth and photoluminescence (PL) of the CsPb1-xCdxBr3 perovskite nanocrystals (NCs) is systematically studied. The x-ray diffraction patterns have shown that cadmium ions are really incorporated into the NCs that results in a decrease in the lattice constant from 5.85 (x = 0) to 5.75 Å (x = 0.45). At the large cadmium content in the glass (x > 0.38), simultaneous formation of the perovskite CsPb1-xCdxBr3 NCs and the non-luminescent CsCdBr3 NCs in the hexagonal phase is found. It is also found that the lattice contraction leads to an increase in the bandgap energy and a noticeable shift of the PL band to the blue region of the spectrum (from 2.42 to 2.68 eV) with a drop in quantum yield from 85% for CsPbBr3 NCs down to 4% for CsPb0.55Cd0.45Br3 NCs. It is shown that the PL quantum yield decreases due to the formation of deep trap states, which manifest themselves as a PL band in the energy range of 1.6-2.5 eV at cryogenic temperatures. A simple model explaining the behavior of the PL band as a function of temperature in the range from 30 to 300 K is proposed.

The coherent spin dynamics of electrons and holes in CsPbI3 perovskite nanocrystals in a glass matrix are studied by the time-resolved Faraday ellipticity technique in magnetic fields up to 430 mT across a temperature range from 6 K to 120 K. The Landé g-factors and spin dephasing times are evaluated from the observed Larmor precession of electron and hole spins. The nanocrystal size in the three studied samples varies from about 8 to 16 nm, resulting in exciton transition varying from 1.69 to 1.78 eV at a temperature of 6 K, allowing us to study the corresponding energy dependence of the g-factors. The electron g-factor decreases with increasing confinement energy in the NCs as a result of NC size reduction, and also with increasing temperature. The hole g-factor shows the opposite trend. Model analysis shows that the variation of g-factors with NC size arises from the transition energy dependence of the g-factors, which becomes strongly renormalized by temperature.

The up-conversion luminescence (UCL) spectra of fluorophosphate glasses doped with a pair of rare earth ions (REI) of ytterbium and thulium in different combinations of their concentrations were studied under continuous excitation at a wavelength of 975 nm. Each of the observed USL bands resulted from the sum of several luminescence processes corresponding to radiation from different excited states of thulium ions. These processes are characterized by different degrees of nonlinearity in the number of required absorbed photons necessary to excite these states. We analyze the influence of pump power and doping ion concentration on the contributions to the UCL spectra caused by excitation processes with various nonlinearities. We found that the appearance of several lines in each of the four spectral regions of ultrasonic luminescence is typical for low concentrations of thulium ions (from a tenth to a thousandth of a percent) and relatively high concentrations of ytterbium ions (from 4 to 10 percent). When the thulium ion concentration was increased to 3 percent with ytterbium ion concentration of 5 percent, the UCL was observed predominantly in the range 755– 840 nm with a maximum near 793 nm.

The spectral properties of inorganic glasses with I-VII and II-VI nanocrystals and quantum dots are investigated. Nanosized copper halide and cadmium chalcogenide crystals stabilized in glass matrix are shown to be a perspective material for nonlinear optical limiting.

Lead halide perovskite nanocrystals (NCs) in a glass matrix combine excellent optical properties and stability against environment. The spectral and temporal characteristics of photoluminescence from CsPbBr3 and CsPb(Cl,Br)3 nanocrystals in a fluorophosphate glass matrix are measured in a temperature range from 6 to 270 K in order to reveal factors that determine their quantum yield and recombination dynamics. At low temperatures, the recombination dynamics is characterized by three decay components with timescales on the order of 1 ns, 10 ns, and 1 mu s. The relative contributions of the corresponding processes and their characteristic times are strongly temperature dependent. The emission intensity decreases with growing temperature. This effect is stronger in smaller NCs, which highlights the role of surface states. These experimental results are discussed on the basis of a model taking into account the NC energy structure and the presence of electron and hole surface trap states. The photoluminescence dynamics at low temperatures is dominated by charge-carrier radiative recombination and relaxation to shallow traps. At temperatures exceeding 100 K, the dynamics is affected by carrier activation to the excited states.

The coherent spin dynamics of holes are investigated for CsPbBr3 and CsPb(Cl, Br)3 perovskite nanocrystals in a glass matrix using the time-resolved Faraday rotation/ellipticity techniques. In an external magnetic field, pronounced Larmor spin precession of the hole spins is detected across a wide temperature range from 5 to 300 K. The hole Land & eacute; g-factor varies in the range of 0.8-1.5, in which it increases with increasing optical transition energy due to enhanced confinement in small nanocrystals. The hole spin dephasing time decreases from 1 ns to 50 ps in this temperature range. Nuclear spin fluctuations have a pronounced impact on the hole spin dynamics. The hyperfine interaction of the holes with nuclear spins modifies their spin polarization decay and induces their spin precession in zero external magnetic field. The results can be well described by the model developed in [I. A. Merkulov et al., Phys. Rev. B 65 , 205309 (2002)], from which the hyperfine interaction energy of a hole spin with the nuclear spin fluctuation in the range of 2-5 mu eV is evaluated.

The fluorophosphate glasses with composition of Ba(PO3)2 - AlF3-CaF2 - MgF2-BaF2 - SrF2-YbF3 - ErF3 were synthesized and their spectroscopic properties were studied. The main attention here was paid to studying the luminescence kinetics Yb3+ (1040 nm) and Er3+ (1550 nm, 655 nm and 540 nm). It has been found that the population of the 4I13/2 (Er3+) level and the relaxation of the 2F5/2 (Yb3+), 4F9/2, and 2H11/2+4S3/2 (Er3+) levels are close to exponential and the probabilities of these processes are well approximated by linear functions with respect to the ytterbium concentration. All this led to the conclusion that the migration-accelerated energy transfer makes a significant contribution to the population and deactivation of these energy levels. A scheme of the main energy transfer channels in an ensemble of ytterbium and erbium ions and the corresponding system of rate equations are proposed. On the basis of these equations, mathematical modeling of the luminescence kinetics of ytterbium and erbium ions was carried out and the energy transfer parameters were estimated.

The tunability of the optical properties of lead halide perovskite nanocrystals makes them highly appealing for applications. Halide anion exchange and quantum confinement enable tailoring of the band gap. For spintronics, the Landé g-factors of electrons and holes are essential. Using empirical tight-binding and k·p methods, we calculate them for nanocrystals of all-inorganic lead halide perovskites CsPbX3 (X = I, Br, Cl). The hole g-factor band gap dependence follows the universal law found for bulk perovskites, while for electrons, a considerable modification is predicted. Based on the k·p analysis, we conclude that this difference arises from the interaction of the bottom conduction band with the spin-orbit split electron states. These predictions are confirmed experimentally for electron and hole g-factors in CsPbI3 nanocrystals in a glass matrix, measured by time-resolved Faraday ellipticity in a magnetic field at cryogenic temperatures.

Up-conversion luminescence (UCL) spectra of fluorophosphate glasses doped with the rare-earth ions Yb3+ with concentrations of 4-10% and Tm3+ with concentrations of 10-5-3% were investigated using continuous-wave excitation at 975 nm. Each of the observed UCL bands was the result of several processes corresponding to various Tm3+ excited states and characterized by a different degree of nonlinearity regarding the number of absorbed photons required to excite these states. The influence of the pumping power and concentrations of doping ions on the contributions to UCL spectra from excitation processes with various nonlinearities was analyzed. The simultaneous appearance of several lines in each UCL spectral region was shown to be typical of low Tm3+ concentrations (fractions of a percent and less) and rather high Yb3+ concentrations (4-10%). UCL appeared primarily in the 755-840-nm band with a maximum near 793 nm if the Tm3+ concentration was increased up to 3% with an Yb3+ concentration of 5%.

The photoluminescence (PL) spectra of CsPbBr3 perovskite nanocrystals grown in a fluorophosphate glass matrix exhibit phonon replicas of the exciton line. The dependence of intensity of the phonon sidebands are simulated taking into account the difference in the curvature of the excited and ground adiabatic potentials. The Raman spectra of CsPbBr3 nanocrystals are measured. Calculations based on the density functional theory is performed to obtain the spectrum of phonon states of these crystals in the orthorhombic phase. The phonon frequencies observed in the PL and Raman spectra are compared with the calculation results.

We report experimental observations of impurity Tm3+ ions upconversion luminescence in fluoroaluminate glasses doped with Yb3+ ions in concentration of 1019-1021 ions/cm3. It was shown that even at extra low concentrations of impurity Tm3+ ions of 1014-2 1017 ions/cm3 there is observable upconversion luminescence of Tm3+ ions. The presence of upconversion luminescence from Tm3+ impurities indicates that Ln3+ ions are clustered in fluoroaluminate glasses. The value of n-parameter of Tm3+ upconversion luminescence band at 475 nm (1G4-*3H6) decreases from 3 to 2 as the excitation power density changes from the range of 2.0-6.0 W/cm2 to the range of 1.4-12.4 kW/cm2. The value of n-parameter indicates that predominant mechanism of energy transfer is cooperative energy transfer from excited Yb-Yb* dimers at high excitation power density and three-stage energy transfer from a single Yb3+ ion to impurity Tm3+ ions at low excitation power.

The spin physics of perovskite nanocrystals with confined electrons or holes is attracting increasing attention, both for fundamental studies and spintronic applications. Here, stable CsPb(Cl_0.56Br_0.44)_3 lead halide perovskite nanocrystals embedded in a fluorophosphate glass matrix are studied by time-resolved optical spectroscopy to unravel the coherent spin dynamics of holes and their interaction with nuclear spins of the 207 Pb isotope. We demonstrate the spin mode locking effect provided by the synchronization of the Larmor precession of single hole spins in each nanocrystal in the ensemble that are excited periodically by a laser in an external magnetic field. The mode locking is enhanced by nuclei-induced frequency focusing. An ensemble spin dephasing time T_2^ * of a nanosecond and a single hole spin coherence time of T 2 = 13 ns are measured. The developed theoretical model accounting for the mode locking and nuclear focusing for randomly oriented nanocrystals with perovskite band structure describes the experimental data very well.

We report on first direct observation of spontaneous fluctuations of birefringence in glasses doped with rare-earth (RE) ions. The fluctuations were observed in Nd3+- and Yb3+-doped glasses as polarization noise of the laser beam transmitted through the sample in the region of the RE-ion absorption. The noise was characterized by a flat ("white") spectrum in the range of frequencies up to 1 GHz and did not show any dependence on magnetic field. The discovered polarization noise is interpreted in terms of structural dynamics of glasses revealed at low temperatures and usually described in the model of tunneling two-level systems (TLS). High sensitivity of the polarization noise technique to this dynamics is related to small homogeneous width of f-f transitions of RE-ions in glasses and small spectral width of the probe laser light. The discovered effect provides a new experimental approach to studying low-temperature structural dynamics of different disordered matrices and interactions of impurities with environment in such media.