Sol-gel Eu3+/Tm3+ doped transparent glass-ceramic waveguides

Eu3+ and Tm3+ doped lanthanum fluoride and lanthanum oxyfluoride are obtained from Eu3+, Tm3+ containing lanthanum fluoracetate solutions. The nature of the crystal phase obtained could be controlled by the temperature of heat treatment. Spectral characteristics of Eu3+ doped crystal phases were sufficiently different to allow utilization of Eu3+ as structural probes. Tm3+ emission at the technologically important spectral region of 1450nm could be observed for the fluoride and oxyfluoride crystal phases. The large bandwidth obtained (around 120nm) suggests potential applications in optical amplification. SiO2-LaF3-LaOF composite materials were also prepared. It is observed that for heat treatments above 800degreesC, fluorine loss, probably in the form of SiF4 hinder the observation of Tm3+ emission. Eu3+ spectroscopic characteristics clearly show the evolution of a fluoride like environment to an amorphous oxide one as the temperature of heat treatment increased. Thin films obtained by dip-coating on V-SiO2 substrates and treated at 300degreesC, 500degreesC and 800degreesC display guided modes in the visible and infrared regions. Optical characteristics (refractive index and films thickness) were obtained at 543.5, 632.8 and 1550nm. Attenuation as low as 1.8dB/cm was measured at 632.8nm. (C) 2004 Published by Elsevier B.V.

Er3+-doped germanate glasses for active waveguides prepared by Ag+/K+ <-> Na+ ion-exchange

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Tungstate fluorophosphate glasses as optical limiters

Nonlinear absorption measurements were performed on fluorophosphate glasses with high concentrations of tungsten oxide. Large two-photon absorption coefficients, alpha(2), were determined at 660 nm using nanosecond laser pulses. It was observed that alpha(2) increases for increasing tungsten oxide concentrations and, hence, the optical limiting performance of this glass composition can be controlled. (C) 2002 American Institute of Physics.

Photopatternable di-ureasil-zirconium oxocluster organic-inorganic hybrids as cost effective integrated optical substrates

Organic-inorganic hybrids containing methacrylic acid (McOH, CH(2)= C(CH(3))COOH)) modified zirconium tetrapropoxide, Zr(OPr(n))(4), classed as di-ureasil-zirconium oxo-cluster hybrids, have been prepared and structurally characterized by X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), Fourier transform infrared (FT-IR) and Raman (FT-Raman) spectroscopies, Si and C nuclear magnetic resonance (NMR), and atomic force microscopy (AFM). XRD and SAXS results have pointed out the presence of Si- and Zr-based nanobuilding blocks (NBBs) dispersed into the organic phase. Inter-NBBs correlation distances have been estimated for the pure di-ureasil and a model compound obtained. by hydrolysis/condensation of Zr(OPr(n))(4):McOH (molar ratio 1: 1): d(Si) approximate to 26 +/- 1 angstrom and d(Zr) approximate to 16 +/- 1 angstrom, respectively. In the case of the di-ureasil-zirconium oxo-cluster hybrids, these distances depend on the Zr relative molar percentage (rel. mol. Zr %) (d(Si) ranges from 18 to 25 angstrom and d(Zr) from 14 to 23 angstrom, as the rel. mol. Zr % increases from 5 to 75), suggesting that the Si- and Zr-based clusters are interconstrained. Complementary data from FT-IR, FT-Raman, (29)Si and (13)C NMR, and AFM support to a structural model where McOH-modified Zr-based NBBs (Zr-OMc) are present over the whole range of composition. At low Zr-OMc contents (rel. mol. Zr % <30) the clusters are well-dispersed within the di-ureasil host, whereas segregation occurs at the 0.1 mu m scale at high Zr-OMc concentration (rel. mol. Zr % = 50). No Zr-O-Si heterocondensation has been discerned. Monomode waveguides, diffractions gratings, and Fabry-Perot cavities have been written through the exposure of the hybrid monoliths to UV light. FT-Raman has shown that the chemical process that takes place under illumination is the polymerization of the methacrylate groups of the Zr-OMc NBBs. The guidance region in patterned channels is a Gaussian section located below the exposed surface with typical dimensions of 320 mu m wide and 88 mu m deep. The effective refractive index is 1.5162 (maximum index contrast on the order of 1 x 10(-4)) and the reflection coeficient of the Fabry-Perot cavity (formed by a grating patterned into a 0.278 cm channel) is 0.042 with a free spectral range value of 35.6 GHz.

PbO-GeO2 rib waveguides for photonic applications

This work presents for the first time to our knowledge the fabrication and characterization of rib waveguides produced with PbO-GeO2 (PGO) thin films. The target was manufactured using pure oxides ( 60 PbO-40 GeO2, in wt%) and amorphous thin films were produced with the RF sputtering technique. PGO thin films present small absorption in the visible and in the near infrared and refractive index of similar to 2.0. The definition of the rib waveguide structure was made using conventional optical lithography followed by plasma etching, performed in a Reactive Ion Etching (RIE) reactor. Light propagation mode in the waveguide structure was analyzed using integrated optic simulation software. Optical loss measurements were performed to determine the propagation loss at 633 nm, for ribs with height of 70 nm and width of 3-5 mu m; experimental values around 2 dB/cm were found for the propagation loss and confirmed the theoretical calculations. The results obtained demonstrate that PGO thin films are potential candidates for application in integrated optics. Published by Elsevier B.V.

Organic-inorganic hybrids prepared by carboxylic acid solvolysis: Planar waveguides

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

Nonresonant third-order nonlinear properties of NaPO3-WO3-Bi2O3 glasses in the near infrared

nonlinear (NL) refractive index, n(2), of NaPO3-WO3-Bi2O3 glass with different relative amounts of the constituents was measured at 1064 and 800 nm using the Z-scan and the thermally managed eclipse Z-scan techniques, respectively. The values of n(2) >= 10(-15) cm(2)/W and negligible NL absorption coefficient were determined. The large values of the NL refractive index and the very small NL absorption indicate that these materials have large potential for all-optical switching applications. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3212972]

Novel fabrication process of planar waveguides in rare-earth doped fluoroindate glasses

We report the successful fabrication of planar waveguides in rare-earth doped fluoroindate glass substrates. A new procedure for waveguide fabrication using a thermally evaporated AgF nonmetallic film was developed. The refractive index changes of more than 0.03, associated to low propagation losses achieved, open new perspectives and show the potentiality of using this glass family toward further developments in fabrication and design of integrated optical devices for optical communication wavelengths.© 1995 American Institute of Physics.

Optical properties of chromium-doped fluoroindate glasses

This work reports on the optical properties of Cr3+ ions in the pseudoternary system InF3-GdF3-GaF3. Linear properties, investigated through absorption and emission spectra, provide information on the crystal field, the frequency, and number of phonons emitted during the absorption to the 4T2 band and the emission to the 4A2 ground state, and the Fano antiresonance line shape in the vicinity of the 4A2→2E transition. A study of the nonlinear refractive index as a function of the wavelength, carried out with the Z-scan technique, provides spectroscopic data about electronic transitions starting from the excited state.

Control of nonlinear absorption and amplification of light in Er3+-doped fluoroindate glass

Nonlinear absorption and amplification of a probe laser beam can be controlled by adjustment of the intensity-modulation frequency and the wavelength of a pump laser beam. A demonstration of this effect in Er3+-doped fluoroindate glass is presented. The results show maximum amplification of the probe beam (∼12%) when a pump laser emitting 16 mW of power is modulated at ∼30 Hz. In the limit of low modulation frequencies, or cw pumping, induced absorption of the probe beam is the dominant nonlinear process. © 1999 Optical Society of America.

Soliton propagation in a medium with Kerr nonlinearity and resonant impurities: A variational approach

The soliton propagation in a medium with Kerr nonlinearity and resonant impurities was studied by a variational approach. The existence of a solitary wave was shown within the framework of a combined nonintegrable system composed of one nonlinear Schrödinger and a pair of Bloch equations. The analytical solution which was obtained, was tested through numerical simulations confirming its solitary wave nature.

Optical limiting behavior of tungstate fluorophosphate glasses

Nonlinear absorption measurements were performed on fluorophosphate glasses with high concentration of tungsten oxide. Large two-photon absorption coefficients, α2, were determined at 660 nm using nanosecond laser pulses. It was observed that α2 increases for increasing tungsten oxide concentrations and therefore the optical limiting performance of this new glass composition can be controlled.

Nonlinear absorption spectrum in perylene derivatives

Knowledge about nonlinear absorption spectra of materials used in photonic devices is of paramount importance in determining their optimum operation wavelengths. In this work, we have investigated the two-photon absorption (2PA) degenerate cross-section spectrum for perylene derivatives using the Z-scan technique with femtosecond laser pulses. All perylene derivatives studied present large 2PA cross-sections, only comparable to the best ones reported in the literature. The results achieved in the present investigation indicate perylene derivatives as promising materials for two-photon applications. ©2005 Optical Society of America.

Photoluminescence-structure relationships in ormosils for integrated optical devices

Planar waveguides with low losses in the infrared (from 0.6-1.1 dB/cm) were prepared with sol-gel derived poly(oxyethylene)/siloxane hybrid doped with zirconium(IV) n-propoxide (ZPO) and methacryloxypropyltrimethoxysilane (MAPTMS). The doped nanohybrids were characterized by small angle X-ray scattering, 29Si nuclear magnetic resonance and photoluminescence spectroscopy and compared with the undoped hybrid material. The results indicate an effective interaction between the zirconium particles and the siliceous nanodomains. © 2005 Materials Research Socicty.

One-dimensional superfluid Bose-Fermi mixture: Mixing, demixing, and bright solitons

We study an ultracold and dilute superfluid Bose-Fermi mixture confined in a strictly one-dimensional (1D) atomic waveguide by using a set of coupled nonlinear mean-field equations obtained from the Lieb-Liniger energy density for bosons and the Gaudin-Yang energy density for fermions. We consider a finite Bose-Fermi interatomic strength gbf and both periodic and open boundary conditions. We find that with periodic boundary conditions-i.e., in a quasi-1D ring-a uniform Bose-Fermi mixture is stable only with a large fermionic density. We predict that at small fermionic densities the ground state of the system displays demixing if gbf >0 and may become a localized Bose-Fermi bright soliton for gbf <0. Finally, we show, using variational and numerical solutions of the mean-field equations, that with open boundary conditions-i.e., in a quasi-1D cylinder-the Bose-Fermi bright soliton is the unique ground state of the system with a finite number of particles, which could exhibit a partial mixing-demixing transition. In this case the bright solitons are demonstrated to be dynamically stable. The experimental realization of these Bose-Fermi bright solitons seems possible with present setups. © 2007 The American Physical Society.