Influence of Stark splitting levels on the lasing performance of Yb(3+) in phosphate and fluorophosphate glasses.

Lasing properties have been investigated for Yb(3+) doped glasses with similar emission cross sections (σ(emi)) and lifetime while possessing different Stark levels. Narrow Stark splitting of Yb(3+)-phosphate glass is responsible for severe heat generation, narrow emission band and much smaller σ(emi) at lasing wavelength, making Yb(3+)-phosphate glass unsuccessful to achieve laser output, whereas 1.166W cw laser was obtained in Yb(3+)-fluorophosphate (FP) glass with broader Stark splitting. Analysis on laser system levels reveals that under room temperature, Yb(3+) laser is quasi-3.13-level in phosphate glass and quasi-3.36-level in FP glass. These demonstrations suggest that unless the Stark splitting is enlarged, conventional Yb(3+)-phosphate glass is not a good gain medium for bulk Yb(3+)-laser.

Violet-green excitation for NIR luminescence of Yb3+ ions in Bi2O3-B2O3-SiO2-Ga2O3 glasses.

60Bi(2)O(3)-20B(2)O(3)-10SiO(2)-10Ga(2)O(3) glasses doped with 1-9 mol% Yb(2)O(3) were prepared and investigated mainly on their violet-green excitation for the typical NIR emission of Yb(3+), generally excited in the NIR. Two violet excitation bands at 365 nm and 405 nm are related to Yb(2+) and Bi(3+). 465 nm excitation band and 480 nm absorption band in the blue-green are assigned to Bi(0) metal nanoparticles/grains. Yb-content-dependence of the excitation and absorption means that Bi(0) is the reduced product of Bi(3+), but greatly competed by the redox reaction of Yb(2+) ↔ Yb(3+). It is proved that the violet-green excitations result in the NIR emission of Yb(3+). On the energy transfer, the virtual level of Yb(3+)-Yb(3+) as well as Bi(0) dimers probably plays an important role. An effective and controllable way is suggested to achieve nano-optical applications by Bi(0) metal nanoparticles/grains and Yb(3+).

Gain structuration in dual-wavelength Nd:YSAG ceramic lasers.

We demonstrate a dual-wavelength Nd:YSAG ceramic laser in which the gain volume is structurated into two different regions providing gain at the wavelength of 1061 nm and 1064 nm respectively. We discuss the role of the nonuniform distribution of the temperature in structurating the gain region via the Boltzmann effect. We show that the two laser wavelengths can be switched by adjusting the size of the pump beam or by slightly modifying the geometrical parameters of the laser cavity, either the length of the cavity or the orientation of a mirror. Additionally, we demonstrate that the transverse modes at the two wavelengths are shaped according to the effect of gain filtering caused by the structuration of the gain region.

Broad combined orange-red emissions from Eu²âº- and Eu³âº-doped low-silica calcium aluminosilicate glass.

In this paper, a broad combined orange-red emission from Eu²âº- and Eu³âº-doped low-silica calcium aluminosilicate (LSCAS) glass is reported. Spectroscopic results demonstrate that it is possible to tune the emission wavelength by changing the excitation wavelength in the UV-Vis region. The color coordinates for the emission spectra were calculated, and using the Commission Internationale de l'Éclairage 1931 and 1976 chromatic diagrams, it is possible to note that they are dependent on the excitation wavelength. In addition, the (u', v') color coordinates for the investigated LSCAS samples are close to the Planckian spectrum in the cold region between 2000 and 2600K. Our results show that the Eu:LSCAS system can be used in a white light phosphor when mixed in aggregate with phosphors using green-yellow luminescent ions.

Complexation-association-extraction spectrophotometric determination of Pt cations based on a multi-reagent analytical system with I- anions and 2-[2-[4-[(2-cyanoethyl)methylamino]phenyl]vinyl]-1,3,3-trimethyl-3H-indolium cations.

A new multi-reagent analytical system with 2-[2-[4-[(2-cyanoethyl)methylamino]phenyl]vinyl]-1,3,3-trimethyl-3H-indolium chloride (CPVTI), which is a styryl hemicyanine cationic dye with good photostability and a high molar absorption coefficient, as its core is first established and utilized successfully to determine the content of Pt ions via a spectrophotometric method. The process involves two treatment steps: adding CPVTI and I solutions to the Pt solution to be detected, and then using butyl acetate for vortex liquid-liquid extraction. A Pt cation can be incorporated into the CPVTI cation with the help of an I- anion, initially converting the Pt cation into a [PtI6]2- complex anion. After forming a [PtI62-·2CPVTI+](aq) ion associate in the aqueous phase, the Pt cation can be extracted selectively by butyl acetate with maximum extraction efficiency, and exists as [PtI62-·2CPVTI+](org) in the extract phase. Via the formation of the iodo-complex of Pt and its ion associate with CPVTI, and the extraction with butyl acetate, Pt is selectively partitioned into the butyl acetate extractant in a step-by-step manner with good interference resistance. In the CPVTI-Pt-I analytical system, the charge state of CPVTI is retained by adjustment with H2SO4; the monovalent CPVTI+ presents a strong spectrophotometric absorbance signal at 530 nm with long-term stability, which allows determination of the Pt content. The system shows a high molar absorption coefficient of 6.52 × 104 L mol-1 cm-1 at 530 nm, a lower limit of detection of 0.07 mg L-1, and a good Sandell's sensitivity of 0.0030 µg cm-2. Mechanistic analysis of the establishment of the system, concentration optimization, standard working curve, system sensitivity and stability, resistance against interference from diverse metal ions, and practical applications are investigated and discussed.

Pretreatment by recyclable Fe3O4@Mg/Al-CO3-LDH magnetic nano-adsorbent to dephosphorize for the determination of trace F- and Cl- in phosphorus-rich solutions.

The magnetic nano-adsorbent Fe3O4@Mg/Al-CO3-LDH (Mg/Al-type layered double hydroxide) with a CO3 2- interlayer anion has been synthesized successfully on Fe3O4 nanoparticles via a urea hydrothermal method. It is confirmed that the nano-adsorbent can adsorb PO4 3- rapidly and efficiently in multi-ion solutions; meanwhile, it did not adsorb any F- and Cl-, even with a high amount of the nano-adsorbent or a longer adsorption time. This behaviour is beneficial for applications to remove PO4 3- in phosphorus-rich solutions, and especially can be utilized to determine trace F- and Cl- anions in phosphorus-rich solutions by physical and chemical analysis methods including ion chromatography without serious interference from PO4 3- for trace determinations. Herein, the hydrothermally synthesized Fe3O4@Mg/Al-CO3-LDH was characterized via SEM, TEM, SAED, XRD, FTIR, magnetic hysteresis loop analysis and adsorption-desorption isotherm analysis. The structure and stability, adsorption mechanism, magnetic saturation value, specific surface area, total pore volume, phosphate adsorption capacity and recyclability are discussed. Using the optimized pretreatment conditions, Fe3O4@Mg/Al-CO3-LDH was utilized successfully to adsorb PO4 3- in real samples and determine trace F- and Cl- accurately by ion chromatography; this would be very beneficial for continuous analysis and on-line tests by physical and chemical analysis methods without interference from PO4 3- in phosphorus-rich samples, leaving F- and Cl- even if in a trace content.

Optical study of Yb(3+)/Yb(2+) conversion in CaF(2) crystals.

Yb(3+) ions with various site symmetries have been observed in the absorption and emission spectra of Yb(3+):CaF(2) crystals, both γ-irradiated and annealed in hydrogen. The absorption intensity value is found to be much higher for the γ-irradiated crystal and strongly dependent on the gamma dose. The UV absorption spectra of γ-irradiated and H(2)-annealed CaF(2):5 at.% Yb(3+) crystals are quite similar. Yb(2+) absorption bands are observed at 360, 315, 271, 260, 227 and 214 nm, which are called A, B, C, D, F and G bands, respectively. For γ-irradiated CaF(2):30 at.% Yb(3+), an additional band at 234 nm can be seen. It is suggested that only a negligible amount of Yb(3+) ions are converted into Yb(2+) under the γ-irradiation. The presence of Yb(2+) is confirmed by the 565 and 540 nm luminescence under 357 nm excitation. It is also suggested that the excitation in the A, C, D and F absorption bands of Yb(2+) gives rise to photo-ionization of Yb(2+) ions and electrons in the conduction band to form the excited Yb(3+) ions which emit IR Yb(3+) luminescence.The UV absorption and emission spectra obtained for γ-irradiated and H(2)-annealed crystals have different structures. This suggests that different mechanisms are responsible for the creation of Yb(2+) ions. γ-irradiation favours Yb(2+) isolated centres by reduction of Yb(3+) ions located at Ca(2+) lattice sites, whereas annealing in hydrogen favours Yb(2+) centres neighbouring Yb(3+) ions when a Yb(3+) ion pair captures a Compton electron. Also, γ-irradiation does not change the position of Yb(3+) ions converted into Yb(2+) in the CaF(2) lattice. In the case of H(2) annealing, a Yb(3+) ion converted to Yb(2+) is shifted to the Ca(2+) position in the lattice.

Structural and spectroscopic properties of Yb³âº-doped MgAl2O4 nanocrystalline spinel.

Magnesium spinel (MgAl2O4) powders doped with Yb(3+) ions have been synthesized by a sol-gel method and heat-treated in the range of 700-1000 °C for 3 h. XRD patterns indicated that the powders have a cubic structure with high crystallite dispersion. Nanoparticles in the range of 10-30 nm are obtained as a function of the dopant concentration and sintering temperature. The main Yb(3+) zero-phonon line is located at 976 nm. The spectroscopic properties of the Yb(3+) ions are characterized by broad absorption spectroscopy and emission spectroscopy. Even at low temperature, the spectra reveal a strong distorted spinel lattice due to the high inversion rate between Mg(2+) tetrahedral sites and Al(3+) octahedral sites. The substitution of Mg(2+) ions by Yb(3+) ions favors the creation of Yb(3+) ion pairs which are observed in the cooperative luminescence spectra at around 500 nm. The luminescence decays are influenced by both the Yb(3+) content, the energy transfer between ions and by the presence of pairs and aggregates. Detailed analysis of the observed structural and spectroscopic measurements has been described in this manuscript.

Spectroscopic characterization of Ti-doped α-ZnAl2S4 spinel-type single crystals.

The spectroscopic characteristics of the α-ZnAl(2)S(4) wide bandgap semiconductor doped with Ti ions are investigated. It is shown, that the ZnAl(2)S(4):Ti spinel-type crystals exhibit luminescence in the IR spectral range 0.8-1.4 µm. The observed spectroscopic characteristics are assigned to the emission bands arising from the ligand -Ti(4+) charge transfer for octahedral sites of titanium that is in agreement with the experimental evidence for the absence of the EPR signal from Ti ions. A qualitative explanation of the experimental data is given.