Unusual broadening of the NIR luminescence of Er3+-doped Nb2O5 nanocrystals embedded in silica host: Preparation and their structural and spectroscopic study for photonics applications

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

EPR, optical absorption and luminescence studies of Cr3+-doped antimony phosphate glasses

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Inorganic Graphenylene: A Porous Two-Dimensional Material With Tunable Band Gap

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Luminescence of Eu3+ in the thin film heterojunction GaAs/SnO2

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Frequency tunable continuous THz wave generation in a periodically poled fiber

An all-fiber approach to terahertz generation using a periodically poled optical fiber is proposed and experimentally demonstrated. In the proposed approach, a continuous-wave THz wave is generated at a periodically poled fiber by beating two optical wavelengths from two laser sources with the wavelength spacing corresponding to the frequency of the THz wave. The key component in the system is the periodically poled fiber, which is made by a twin-hole fiber with the fiber core residing between two holes. The twin-hole fiber is then thermally poled at a temperature of similar to 260 degrees C with a voltage of 3.3 kV applied to the silver electrodes inside the two holes to introduce second-order nonlinearity. The quasi phase matching (QPM) condition is achieved by periodically erasing the thermal poling induced second-order nonlinearity with an ultraviolet laser, which enhances the energy conversion efficiency. The proposed approach is validated by an experiment. The emission of a THz wave centered at 3.8 THz with an output power of 0.5 mu W is observed. The frequency tunability between 2.2 and 3.8 THz is also experimentally demonstrated.

Two-dimensional nonlinear map characterized by tunable Levy flights

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

MnO4(3-) NIR luminescence in Ba2SiO4

Ba2SiO4: MnO43- luminescence is reported and compared to similar host lattices based on PO43-, VO43- and AsO43-, where Mn5+ substitutes for p(5+),V5+ Or AS(5+). The observed energy position of MnO43- 1E state in SiO44- is in accordance with interelectronic repulsion caused by Mn5+-O bond length. At 77 K the E-1 splitting is 119 cm(-1), which is in agreement with 1.8 degrees, the average deviation of O-M-O angles from the regular tetrahedron. These values are adjusted to Ca point symmetry. The vibronic-structure spectra evidenced a progression with a frequency assigned to the nu(2)(E) bending mode of MnO43-.

Luminescence properties of Eu-complex formations into ordered mesoporous silica particles obtained by the spray pyrolysis process

Ordered mesoporous, highly luminescent SiO2 particles have been synthesized by spray pyrolysis from solutions containing tetraethylorthosilicate (TEOS), Eu(NO3)3.6H2O, and cetyltrimethylammonium bromide (CTAB) as structure-directing agents. The 1,10-phenantroline (Phen) molecules were coordinated in a post-synthesis step by a simple wet impregnation method. In addition, other matrices were also prepared by the encapsulation of europium complex Eu(fod)3 (where fod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) into mesoporous silica, and then the Phen molecules were encapsulated by different impregnation steps, after which the luminescence properties were investigated. The obtained materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder x-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Powders with polydisperse spherical grains were obtained, displaying an ordered hexagonal array of mesochannels. Luminescence results revealed that Phen molecules had been successfully coordinated as an additional ligand in the Eu(fod)3 complex into the channels of the mesoporous particles without disrupting the structure.

Temperature Dependent Luminescence Spectra of Synthetic and Natural Alexandrite

Results of photoluminescence measurements for natural and synthetic alexandrite (BeAl2O4:Cr3+) are presented, where the samples are excited by the 488 nm line of an Ar+ laser, at different temperatures. The main issue is the analysis of the Cr3+ transition in the chrysoberyl matrix (BeAl2O4), with major technological application as active media for laser action. Results indicate anomalous behavior of Cr3+ transition depending on the measurement temperature. A simple model to explain the phenomena is suggested.

Effect of silica surface on luminescence properties of tb3+-glutamic acid.

We studied the effect of silica surface on luminescence properties of terbium complex by spectroscopy characterization, where microparticles of mesoporous silica type MSU-X was prepared. We used silica with different surface: calcined, washed, functionalized with 3- aminopropyl-triethoxysilane (APTES), and 3-glycidoxypropyl-trimethoxysilane (GPTMS); impregnated with Tb3+-glutamic acid complex. The obtained materials were characterized by scanning electron microscopy, porosity measurements, small-angle X-ray scattering, as structural characterization; Fourier transform infrared and luminescence spectroscopy, as spectroscopy characterization. Finally, we observed that functional groups at the silica surface lead to changes on luminescent properties of the final materials. The observed shift of the absorption and emission bands can be assigned to the effect of the functional groups of mesoporous silica.