Active planar waveguides based on sol-gel Er3+-doped SiO2-ZrO2 for photonic applications: Morphological, structural and optical properties

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

Er(3+) doped phosphoniobate glasses and planar waveguides: structural and optical properties

Phosphoniobate glasses with composition (mol%) (100-x) NaPO(3)-xNb(2)O(5) ( x varying from 11 to 33) were prepared and characterized by means of thermal analysis, Fourier transform infrared spectroscopy, Raman scattering and (31)P nuclear magnetic resonance. The addition of Nb(2)O(5) to the polyphosphate base glass leads to depolymerization of the metaphosphate structure. Different colors were observed and assigned as indicating the presence of Nb(4+) ions, as confirmed by electron paramagnetic resonance measurements. The color was observed to depend on the glass composition and melting temperature as well. Er(3+) containing samples were also prepared. Strong emission in the 1550 nm region was observed. The Er(3+4)I(15/2) emission quantum efficiency was observed to be 90% and the quenching concentration was observed to be 1.1 mol%( 1.45 x 10(20) ions cm(-3)). Planar waveguides were prepared by Na(+)-K(+)-Ag(+) ion exchange with Er(3+) containing samples. Optical parameters of the waveguides were measured at 632.8, 543.5 and 1550 nm by the prism coupling technique as a function of the ion exchange time and Ag(+) concentration. The optimized planar waveguides show a diffusion depth of 5.9 mu m and one propagating mode at 1550 nm.

Structure and optical properties of [Ba1-xY2x/3](Zr0.25Ti0.75)O-3 powders

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

(Sr,Tm)ZrO3 powders prepared by the polymeric precursor method: Synthesis, optical properties and morphological characteristics

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Structural refinement, optical and microwave dielectric properties of BaZrO3

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

Photoluminescence in quasi-amorphous Pb0.8X0.2Zr0.53Ti0.47O3 (X = Ca, Sr and Ba) powders: An optical and structural study

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

Optical and dielectric relaxor behaviour of Ba(Zr0.25Ti0.75)O-3 ceramic explained by means of distorted clusters

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Microstructured chalcogenide optical fibers from As2S3 glass: towards new IR broadband sources

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

HMDSO plasma polymerization and thin film optical properties

Thin films were deposited from hexamethyldisiloxane (HMDSO) in a glow discharge supplied with radiofrequency (rf) power. Actino-metric optical emission spectroscopy was used to follow trends in the plasma concentrations of the species SiH (414.2 nm), CH (431.4 nm), CO (520.0 nm), and H (656.3 nm) as a function of the applied rf power (range 5 to 35 W). Transmission infrared spectroscopy (IRS) was employed to characterize the molecular structure of the polymer, showing the presence of Si-H, Si-O-Si, Si-O-C and C-H groups. The deposition rate, determined by optical interferometry, ranged from 60 to 130 nm/min. Optical properties were determined from transmission ultra violet-visible spectroscopy (UVS) data. The absorption coefficient α, the refractive index n, and the optical gap E04 of the polymer films were calculated as a function of the applied power. The refractive index at a photon energy of 1 eV varied from 1.45 to 1.55, depending on the rf power used for the deposition. The absorption coefficient showed an absorption edge similar to other non-crystalline materials, amorphous hydrogenated carbon, and semiconductors. For our samples, we define as an optical gap, the photon energy E04 corresponding to the energy at an absorption of 104 cm-1. The values of E04 decreased from 5.3 to 4.6 as the rf power was increased from 5 to 35 W. © 1995.

Time-resolved Z-scan and thermal lens measurements in Er+3 and Nd+3 doped fluoroindate glasses

In rare earth ion doped solids, a resonant non-linear refractive index, n2, appears when the laser pumps one of the ion excited states and the refractive index change is proportional to the excited state population. In these solids there are usually thermal and non-thermal lensing effects, where the non-thermal one is due to the polarizability difference, Δα, between excited and ground states of the ions. We have used the time resolved Z-scan and a mode-mismatched thermal lens technique with an Ar+ ion laser in Er+3 (20ZnF2-20SrF2-2NaF-16BaF2-6GaF3-(36 - x)InF3-xErF3, with x= 1, 2, 3 and 4 mol%) and Nd+3 (20SrF2-16BaF2-20ZnF2-2GdF3-2NaF-(40 - x)InF3-xNdF3, with x = 0.1, 0.25, 0.5-1 mol%) doped fluoroindate glasses. In both samples we found that the non-linear refraction is due to the thermal effect, while the non-thermal effect is negligible. This result indicates that in fluoride glasses Δα is very small (less than 10-26 cm3). We also measured the imaginary part of the non-linear refractive index (n″2) due to absorption saturation.

Electrical and optical characteristics of SnO2 thin films prepared by dip coating from aqueous colloidal suspensions

Starting from aqueous colloidal suspensions, undoped and Nb5+ doped SnO2 thin films have been prepared by using the dip-coating sol gel process. X-ray diffraction results show that films are polycrystalline with crystallites of average size1-4nm. Decreasing the thickness of the films and increasing the Nb5+ concentration limits the crystallite size growth during firing. Complex impedance measurements reveal capacitive and resistive effects between adjacent crystallites or grains, characteristic of electrical potential barriers. The transfer of charge throughout these barriers determines the macroscopic electrical resistance of the layer. The analysis of the optical absorption spectra shows that the samples present more than 80% of their transmittance in the visible region and the value of the band gap energy increases with decreasing crystallite size. © 1997 Chapman & Hall.

Magneto-optical rotation of heavy-metal oxide glasses

Magneto-optical rotation was measured at room temperature for glasses containing Bi2O3-CdO-GeO2 (BCG), and Bi2O3-PbO-GeO2-B2O3 (BPGP). A pulsed magnetic field between 50 and 80 KG was used to measure Faraday rotation at 632.8 nm as a function of the concentration of Bi and Cd for BCG and Bi and Pb for BPGB. Verdet constant as high as 0.162 min G-1 cm-1 at 632.8 nm for the BPGB sample with the highest concentrations of Bi and Cd was found. Verdet constant increases linearly with the heavy-metal concentration for the BPGB whereas it reaches some saturation for the BCG system. Measurements of the magneto-optical rotation at other wavelengths in the visible and the refractive index at 632.8 nm are also reported. © 1998 Elsevier Science B.V. All rights reserved.

Absorption and fluorescence of Er3+-doped LiYF4: Measurements and simulation

Er3+:LiYF4 single crystal has been studied by absorption and fluorescence spectroscopy in the IR-visible-UV (0-44000 cm-1) region from 4.2 K to room temperature. Polarized spectra were recorded in order to assign numerous Stark levels of electronic transitions mentioned but not attributed before in the related literature and to discuss the irreducible representations (irreps) of the 4I15/2 sublevels. A parametric hamiltonian, including free ion (Eν, α, β, γ, Tλ, ζ, Mk and Pi) and crystal field parameters (B2 0, B4 0, B4 4, B6 0 and B6 4) in an approximate D2d symmetry for the rare earth site in this scheelite type structure, was used to simulate 109 energy positions of the Er ion with a r.m.s. standard deviation of 14.6 cm-1. A comparison with previously published results for Nd3+ in the same matrix is done. © 1998 Elsevier Science S.A.

An N2: CH4: H2O DC glow discharge plasma probed by optical and electric techniques: significance to the radiation chemistry of Titan's upper atmosphere in the presence of meteoritic water

This paper presents optical and electrical measurements on plasma generated by DC excited glow discharges in mixtures composed of 95% N2, 4.8% CH4 and 0.2% H2O at pressures varying from 1.064 mbar to 4.0 mbar. The discharges simulate the chemical reactions that may occur in Titan's atmosphere in the presence of meteorites and ice debris coming from Saturn's systems, assisted by cosmic rays and high energy charged particles. The results obtained from actinometric optical emission spectroscopy, combined with the results from a pulsed Langmuir probe, show that chemical species CH, CN, NH and OH are important precursors in the synthesis of the final solid products and that the chemical kinetics is essentially driven by electronic collision processes. It is shown that the presence of water is sufficient to produce complex solid products whose components are important in prebiotic compound synthesis. © 1998 Elsevier Science Ltd. All rights reserved.

Crystallographic, dielectric and optical properties of SrBi 2Ta2O9 thin films prepared by the polymeric precursor method

Strontium bismuth tantalate thin films were prepared on several substrates (platinized silicon (Pt/Ti/SiO 2 /Si), n -type (100)-oriented and p -type (111)-oriented silicon wafers, and fused silica) by the solution deposition method. The resin was obtained by the polymeric precursor method, based on the Pechini process, using strontium carbonate, bismuth oxide, and tantalum ethoxide as starting reagents. Characterizations by XRD and SEM were performed for structural and microstructural evaluations. The electrical measurements, carried on the MFM configuration, showed P r values of 6.24 μC/cm 2 and 31.5 kV/cm for the film annealed at 800 C. The film deposited onto fused silica and treated at 700 C presented around 80% of transmittance. © 2002 Taylor & Francis.