Eugenio Rodriguez

University of Campinas, Campinas, Estado de Sao Paulo, Brazil

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Publications (10)11.1 Total impact

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    ABSTRACT: The structure of thin films composed of a multilayer of PbTe nanocrystals embedded in SiO2, named as PbTe(SiO2), between homogeneous layers of amorphous SiO2 deposited on a single-crystal Si(111) substrate was studied by grazing-incidence small-angle X-ray scattering (GISAXS) as a function of PbTe content. PbTe(SiO2)/SiO2 multilayers were produced by alternately applying plasma-enhanced chemical vapour deposition and pulsed laser deposition techniques. From the analysis of the experimental GISAXS patterns, the average radius and radius dispersion of PbTe nanocrystals were determined. With increasing deposition dose the size of the PbTe nanocrystals progressively increases while their number density decreases. Analysis of the GISAXS intensity profiles along the normal to the sample surface allowed the determination of the period parameter of the layers and a structure parameter that characterizes the disorder in the distances between PbTe layers.
    Journal of Applied Crystallography 06/2010; 43(3). · 3.34 Impact Factor
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    ABSTRACT: The stack-and-draw technique has been used to fabricate photonic crystal fibers (PCFs) from four different types of soft glass, namely, borosilicate, alkaline, lead, and tungsten–tellurite. The thermophysical properties of the components must be matched in order to produce PCFs from a combination of glass types. Lead/alkaline PCFs could be fabricated without crystallization or fragility problems. Using borosilicate glass alone, PCFs with up to five hollow periodic structures could be formed. With tungsten–tellurite glass, a PCF with one hollow periodic structure and a core doped with Er3+ ions have been produced. The properties of this fiber confirm its potential application in optical amplification or in other active devices.
    Journal of the American Ceramic Society 11/2009; 93(2):456 - 460. · 2.11 Impact Factor
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    ABSTRACT: Tellurite glasses are important as a host of Er3+ ions because of their good solubility and because they present broadband optical gain compared with Er3+-doped silica, with the potential to increase the bandwidth of communication systems. However, the small glass stability range (GSR) of tellurite glasses compromises the quality of the optical fibers. We show that the addition of CsCl to tellurite glasses can increase their GSR, making it easier to draw good-quality optical fibers. CsCl acts like a network modifier in glass systems, weakening the network by forming Te–Cl bonds. We show that the thermal expansion coefficient mismatch is in the right direction for optical fiber fabrication purposes and that the Bi2O3 content can be used to control the refractive index of clad and core glasses. Single-mode and multi-mode Er3+-doped optical fibers were produced by the rod-in-tube method using highly homogeneous TeO2–ZnO–Li2O–Bi2O3–CsCl glasses.
    Journal of the American Ceramic Society 05/2007; 90(6):1822 - 1826. · 2.11 Impact Factor
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    Spie Newsroom. 01/2007;
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    ABSTRACT: A double tweezers setup was employed to perform ultra sensitive force measurements and to obtain the full optical force curve as a function of radial position and wavelength. The light polarization was used to select either the transverse electric (TE), or transverse magnetic (TM), or both, modes excitation. Analytical solution for optical trapping force on a spherical dielectric particle for an arbitrary positioned focused beam is presented in a generalized Lorenz-Mie diffraction theory. The theoretical prediction of the theory agrees well with the experimental results. The algorithm presented here can be easily extended to other beam geometries and scattering particles. (c) 2006 Optical Society of America.
    Optics Express 11/2006; 14(26):13101-13106. · 3.55 Impact Factor
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    ABSTRACT: Thermal Lens (TL) and spectroscopic characterizations were performed in 70TeO2-19WO3-7Na2O-4Nb2O5 (mol%) tellurite glasses. TL measurements were accomplished in Er3+ /Tm3+ co-doped tellurite glasses in function of the Tm2O3 concentration (0.4-1.6 x1020 ions/cm3). Fluorescence spectra at 488 nm showed that Er3+ /Tm3+ co-doped tellurite glasses present several emission bands between (500-1800) nm. However, the more intense emission bands correspond to the Tm3+ and Tm3+ transitions (4I13/2 --> 4I15/2 and 3F4 --> 3H6), respectively. The absolute nonradiative quantum efficiency (phi) was determined by TL method. Higher values of phi were obtained with the increase of Tm2O3 concentration inside of the Er3+/Tm3+ co-doped tellurite glasses. These results are corroborated by the Judd-Ofelt calculations.
    01/2006;
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    ABSTRACT: In this work we present the fabrication of tellurite glass photonic crystal fiber doped with a very large erbium concentration. Tellurite glasses are important hosts for rare earth ions due to its very high solubility, which allows up to 10,000 ppm Er3+ concentrations. The photonic crystal optical fibers and tellurite glasses can be, therefore, combined in an efficient way to produce doped fibers for large bandwidth optical amplifiers. The preform was made of a 10 mm external diameter tellurite tube filled with an array of non-periodic tellurite capillaries and an erbium-doped telluride rod that constitute the fiber core. The preform was drawn in a Heathway Drawing Tower, producing fibers with diameters between 120 - 140 mum. We show optical microscope photography of the fiber"s transverse section. The ASE spectra obtained with a spectra analyzer show a red shift as the length of the optical fiber increases.
    Proc SPIE 04/2005;
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    ABSTRACT: Thin films of glass doped with PbTe quantum dots were successfully fabricated. The semiconducting quantum dots were grown by laser ablation of a PbTe target (99.99%) using the second harmonic of a Q-Switched Quantel Nd:YAG laser under high purity argon atmosphere. The glass matrix was fabricated by a plasma chemical vapor deposition method using vapor of tetramethoxysilane (TMOS) as precursor. The QD's and the glass matrix were alternately deposited onto a Si (100) wafer for 60 cycles. Cross-section TEM image clearly showed QD's layer well separated from each other with glass matrix layers. The influence of the ablation time on the size distribution of the quantum dots is studied. HRTEM revealed anisotropy in the size of the QD's: they were about 9nm in the high and 3-5 in diameter. Furthermore HRTEM studies revealed that the QD's basically growth in the (200) and (220) directions. The thickness of the glass matrix layer was about 20 nm. Absorption, photo luminescence and relaxation time of the multilayer were also measured.
    Proc SPIE 04/2005;
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    ABSTRACT: Tellurite glasses optical fibers became promising for optical amplifiers due to its high rare earth ions solubility. One of the most important parameter for optical amplification is the lifetime of the excited states, which strongly depends on the crystal field around the ions. That crystal field changes dramatically with the host glass and with rare earth concentration. Excited state lifetime studies have been performed on Er3+-doped-TeO2-WO3-Na2O-Nb2O5 glass system. Therefore, we decided to study the Er3+ excited states lifetimes and compared with the Judd-Ofelt theory predictions. We measured only the 4I13/2 to 4I15/2 transitions lifetimes. The other transitions lifetimes can be inferred by knowing the Omega2, Omega4, Omega6 Judd-Ofelt parameters. These parameters were calculated with the electric-magnetic dipole transition oscillator strength for the desired excited levels and ground state obtained from the optical absorption spectra. After performing this calculation we estimated that maximum quantum efficiency (eta), measured/calculated lifetimes ratio, would be achieved at 7500ppm (%wt) Er3+ content.
    Proc SPIE 04/2005;
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    ABSTRACT: Tellurite glasses optical fibers became promising for optical amplifiers due to its high rare earth ions solubility and very large amplification bandwidth. Among several tellurite glasses the TeO2-WO3-Na2O-Nb2O5 system show one of the largest bandwidth. Our previous characterization of lifetime using the omega2, omega4, omega6, Judd-Ofelt parameters indicate a quantum efficiency maximum for 7500ppm Er3+ concentration. Therefore we decided to produce jointed Er3+ and Tm3+ single mode optical fibers with this glass system keeping the 7500ppm Er3+ concentration and varying the Tm3+ concentration from 2500ppm to 15000ppm. This single mode fiber was pumped by 120mW of the semiconductor laser at 790nm and we observed a flat ASE bandwidth from 1400 to 1570nm for the 5000ppm Tm3+ concentration.
    Proc SPIE 04/2005;