Luminescence Properties and Decay Kinetics of Mn 2+ and Eu 3+ Co-Dopant Ions in MgGa 2 O 4 Ceramics

A. Luchechko gratefully acknowledges a grant from the Institute of Physics PAS for a research visit to the institute, while A.I. Popov has been supported by project LZP-2018/1-0214 from the Latvian Council of Science.The MgGa 2 O 4 ceramics co-doped with Mn 2+ and Eu 3+ ions were synthesized via a higherature solid-state reaction technique. The samples with various Eu 3+ concentrations were characterised using high-resolution photoluminescence (PL) spectroscopy. The PL spectra show weak matrix emission in a blue spectral region with dominant excitation band around 380 nm. Manganese ions are highly excited deeply in UV region and exhibit emission band peaked at 502 nm. The Eu 3+ ions show characteristic f-f excitation and emission lines. The energy transfer between host defects and activator ions was observed. Luminescence decay curves of Mn 2+ and Eu 3+ emission showed complex kinetics with both Eu 3+ -ion concentration and excitation wavelength changes.Latvian Council of Science LZP-2018/1-0214; Latvian–Ukrainian Joint Research Project LV-UA/2016/1,M/.8-2018; project DB/RIDER0117U004443; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Peculiarities of valence band formation in As-Ge-Se semiconductor glasses

Peculiarities of valence bands formation in As-Ge-Se semiconductor glasses have been investigated within AsxGexSe₁₋₂x cut of glass forming region by highresolution X-ray photoelectron spectroscopy (XPS). It is shown that compositional dependence of XPS valence band spectra of the investigated glasses correlates well with previously obtained data for constituent glasses of binary GexSe₁₋x and AsxGe₁₋x systems. In particular, increase in х leads to the decrease in the intensity of bands at ~2 eV responsible for Se lp-states. The valley at ~3 eV is filled by electronic states originated from Se-GE and Se-As bonds. An accompanying decrease in the intensity of the band at ~5 eV is explained by a decrease in Se 4p bonding states associated with covalent bonds

Modeling and optimization of the YAG:Yb microchip laser passively Q-switched by YAG:Cr absorber

Based on analytical and numerical solutions of the rate equations system and the heat conductivity equation, the model of the quasi-three-level passively Q-switched YAG:Yb/YAG:Cr microchip laser is developed. The obtained results are used for its optimization, i.e., for the determination of the output mirror reflectivity, the pumping beam radius, the thickness of the absorber and the phototropic centers concentration maximizing the energy in the laser pulse. The influence of the thermal load on the spatial parameters of the laser beam is also determined

Induced Absorption in Gadolinium Gallium Garnet Irradiated by High Energy 235U^{235}U Ions

The present work is devoted to investigation of optical absorption in pure $Gd_{3}Ga_{5}O_{12}$ (GGG) single crystals in the spectral range 0.2-1.1 μm induced under influence of the $\text{}^{235}U$ ions irradiation with energy 2640 MeV and a fluence $10^{9}-10^{11} cm^{-2}$. The induced absorption for $10^{9} cm^{-2}$ is caused by recharging of point defects, both growth ones and impurities. After irradiation by $\text{}^{235}U$ ions with fluences starting from $3 \times 10^{9} cm^{-2}$ the absorption rise is probably caused by contribution of the lattice destroying as a result of heavy ion bombardment as well as radiation displacement defects

Optical in situ Study of Reduction/Oxidation Processes in Cr,Mg:YAG Epitaxial Film

The changes of the optical absorption spectra of Cr,Mg:YAG epitaxial film caused by high-temperature redox treatment are investigated by means of in situ spectroscopy. The spectra were registered in the visible and near-IR spectral regions at temperatures up to 1100 K. The kinetics of optical absorption changing were obtained in the temperature range from 936 K to 1091 K and were described by mathematical model connecting the chromium recharging process with oxygen vacancies diffusion. The parameters of the model were determined from the approximations of the experimental kinetics

Optical Properties of GGG Epitaxial Films Grown from PbO-B 2

The paper reports a growth of the high-quality Gd₃Ga₅O₁₂ (GGG) homoepitaxial films by the liquid phase epitaxy technique using the PbO-B₂O₃ and PbO-B₂O₃-V₂O₅ fluxes. The influence of the flux composition containing V₂O₅ as well as the growth temperature is discussed basing on the optical absorption and the electron probe micro analysis results

Optical Properties of GGG Epitaxial Films Grown from PbO-B₂O₃-V₂O₅ Flux

The paper reports a growth of the high-quality Gd₃Ga₅O₁₂ (GGG) homoepitaxial films by the liquid phase epitaxy technique using the PbO-B₂O₃ and PbO-B₂O₃-V₂O₅ fluxes. The influence of the flux composition containing V₂O₅ as well as the growth temperature is discussed basing on the optical absorption and the electron probe micro analysis results

Eight-Channel Optical Add Drop Multiplexer Based on Ring Resonator Using LNOI Channel Waveguides

In this paper we report on an eight-channel optical add drop multiplexer based on ring resonator using lithium niobate on insulator channel waveguides. It is suitable for a DWDM-GPON network with channel spacing of 100 GHz in C-band and data rate is 10 Gbps. The insertion loss at the drop port is maximum 1.2 dB and the Q-factor is 1636. It can be used as multiplexer as well as demultiplexer in 8-channel DWDM systems