~ 1.2 μm near-infrared emission and gain anticipation in Ho doped heavy-metal gallate glasses

Ho³⁺-doped low-phonon-energy heavy-metal gallate glasses (LKBPBG) have been prepared and efficient 1.199 μm emission originating from the ⁵I₆ → ⁵I₈ radiative transition has been observed under 900 nm excitation. The spontaneous emission probability and the maximum stimulated emission cross-section were derived to be 294.31 s^{− 1} and 3.46 × 10^{− 21} cm², respectively. The ratio of quantum yields between ~ 1.2 and ~ 2.0 μm emissions was identified to be 16%, demonstrating that the ⁵I₆ → ⁵I₈ transition is favorable for optical amplification. The maximum gain coefficient of 1.84 dB/cm at 1.199 μm wavelength was anticipated in the ideal status. These results indicate that the Ho³⁺-doped LKBPBG glasses have a promising potential for the development of ~ 1.2 μm signal amplifier devices.     

EPR and photoacoustic studies on 30 kev H ion-implanted n-GaAs

Electron paramagnetic resonance (EPR) measurements are carried out on the 30 keV H⁺ion-implanted, Si-doped GaAs(1 0 0) for various doses from 10¹⁴ to 10¹⁷ cm^−2. The results are correlated with photoacoustic and photoluminescence measurements. All the measurements confirm the sign change of charge carrier at a dose of 10¹⁵ cm^−2.     

Shocks and cold fronts in galaxy clusters

The currently operating X-ray imaging observatories provide us with an exquisitely detailed view of the Megaparsec-scale plasma atmospheres in nearby galaxy clusters. At z&amp;lt;0.05<math altimg="si33.gif" overflow="scroll"><mi>zmi><mo>&amp;lt;mo><mn>0.05mn>math>, the m>Chandra &amp;#xA0;m>'s 1^&amp;Prime;<math altimg="si34.gif" overflow="scroll"><msup><mrow><mn>1mn>mrow><mrow><mo>&amp;Prime;mo>mrow>msup>math> angular resolution corresponds to linear resolution of less than a kiloparsec, which is smaller than some interesting linear scales in the intracluster plasma. This enables us to study the previously unseen hydrodynamic phenomena in clusters: classic bow shocks driven by the infalling subclusters, and the unanticipated &amp;ldquo;cold fronts,&amp;rdquo; or sharp contact discontinuities between regions of gas with different entropies. The ubiquitous cold fronts are found in mergers as well as around the central density peaks in &amp;ldquo;relaxed&amp;rdquo; clusters. They are caused by motion of cool, dense gas clouds in the ambient higher-entropy gas. These clouds are either remnants of the infalling subclusters, or the displaced gas from the cluster's own cool cores.     

Cs^＋-K^＋ Exchange in Z-Cut KTiOPO4 Crystal Covered with Chromium Masking Layer

Cs^＋-K^＋ ion exchanges are performed on z-cut KTiOPO4 crystals with chromium coating covered. The temperature of ion exchange is 430℃, and the time range from 15min to 30min. The dark mode spectra of the samples are measured by the prism coupling method. The channel structures on the samples are observed by a microscope and the near field pattern of the channel waveguides are measured by the end-fire coupling method. The refractive index of the samples increases and the increments at surface are modulated due to the existence of Cr film. In the region covered by Cr film, the refractive index of the samples at the surface increases dramatically in a shallow layer. The results of energy dispersive x-ray spectra indicate that in the region covered with Cr film, Cr ions participate in the ion exchange process, and enhance the refractive index. The results may provide a possibility that achieves index enhancement and Cr doping synchronically.     

The structural and optical properties of ZnO/Si thin films by RTA treatments

ZnO/Si thin films were prepared by rf magnetron sputtering method and some of the samples were treated by rapid thermal annealing (RTA) process at different temperatures ranging from 400 to 800&amp;#xA0;&amp;deg;C. The effects of RTA treatment on the structural properties were studied by using X-ray diffraction and atomic force microscopy while optical properties were studied by the photoluminescence measurements. It is observed that the ZnO film annealed at 600&amp;#xA0;&amp;deg;C reveals the strongest UV emission intensity and narrowest full width at half maximum among the temperature ranges studied. The enhanced UV emission from the film annealed at 600&amp;#xA0;&amp;deg;C is attributed to the improved crystalline quality of ZnO film due to the effective relaxation of residual compressive stress and achieving maximum grain size.     

Synthesis, microstructure and photoluminescence of Eu/Tb activated Y2SiO5 nanophosphors by new silicate sources

Y_{2&amp;minus;m>xm>}Tb_m>xm>SiO₅ and Y_{2&amp;minus;m>xm>}Eu_m>xm>SiO₅ nanophosphors with seven different kinds of silicate sources were synthesized by sol-gel method. The structures have been investigated to be composed of nanometer-size grains of 30-60&amp;#xA0;nm through X-ray diffraction (XRD) and scanning electron microscopy (SEM) was used to compare the different morphology of patterns from seven different silicon sources. The photoluminescence of Y_{2&amp;minus;m>xm>}Tb_m>xm>SiO₅ was investigated as a function of silicate sources and the results revealed that these nanometer materials showed the characteristic emission ⁵D₄&amp;#xA0;&amp;rarr;&amp;#xA0;⁷F_m>Jm> (m>Jm>&amp;#xA0;=&amp;#xA0;6, 5, 4, 3) of Tb ions. The characteristic emission ⁵D₀&amp;#xA0;&amp;rarr;&amp;#xA0;⁷F_m>Jm> (m>Jm>&amp;#xA0;=&amp;#xA0;1, 2, 4) of Eu ions was also found in the materials of Y_{2&amp;minus;m>xm>}Eu_m>xm>SiO₅.     

Near-field scanning optical microscopy studies of thin film surfaces and interfaces

In this article, the results of the modeling of topography related artifacts appearing in near-field scanning optical microscopy measurements are presented. The results obtained for near-field scanning optical microscope operation in reflection mode with off-axis far field detector position are compared with experimental results. It is shown that the chosen numerical method - Finite Difference in Time Domain method (FDTD) - can be used for efficient modeling of main topography related artifact. It is also seen that the far field detector position can have large influence on the resulting reflection mode optical images.     

A new blue-emitting phosphor, SrZnO2:Pb, synthesized by the adipic acid templated sol-gel route

A new blue-emitting phosphor, Sr_1&amp;minus;m>_xm>Pbm>_xm>ZnO₂, was prepared by a novel adipic acid templated sol-gel route. Photoluminescence and crystalline properties were investigated as functions of calcination temperatures and the Pb²⁺ doping levels. It was found that under UV excitation with a wavelength of 283 or 317&amp;#xA0;nm, the phosphors gave emission from 374 to 615&amp;#xA0;nm with a peak centered at 451&amp;#xA0;nm. This broad-band was composed of UV and the visible range was attributed to an impurity-trapped exciton-type emission. The maximum emission intensity of the Sr_1&amp;minus;m>_xm>Pbm>_xm>ZnO₂ phosphors occurred at a Pb concentration of m>xm>=0.01. The decay time was observed to be &amp;sim;33&amp;#xA0;ms for the compound doped with 1&amp;#xA0;mol% Pb prepared at 1000&amp;#xA0;&amp;deg;C. Diffuse reflectance spectra revealed the characteristic absorption peaks and the bandgap energy of SrZnO₂ was found to be 3.4&amp;#xA0;eV. SEM analysis indicated that phosphor particles have an irregularly rounded morphology and the average particle size was found to be approximately 1&amp;#xA0;μm.     

Electron-vibrational interaction in 4f-5d optical transitions in Ba, Ca, Sr thiogallates doped with Eu ions

This study is devoted to the problem of the electron-vibrational interaction in 4f-5d optical transitions. We analyze the room temperature experimental data on the vibronically assisted broad bands arising from the 4f-5d transitions in Ba, Ca, and Sr thiogallates doped with Eu²⁺ ions. An approximate simple expression is given for the shape function of the broad vibronic bands with allowance for the terms corresponding to the emission (absorption) from both ground and first excited vibrational levels. We estimate the vibronic coupling parameters and the Stokes shifts for these systems. The theoretical results are in a good agreement with the experimental data.