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Polycrystalline Zn2TiO4 samples with Mn2+ doping level of 0%, 0.1%, 1.0%, and 5.0% have been produced by conventional solid-state method and their optical and structural properties investigated. Rietveld refinement of x-ray diffraction patterns revealed the formed phases and the crystallographic parameters. The chemical composition was obtained by x-ray fluorescence measurements. The optical properties were studied by photoluminescence, excitation, reflectance, and photoacoustic spectroscopy. All measurements were performed at room temperature. The photoluminescence spectrum of the pure sample (0% Mn2+) showed a band in the red region associated with Zn2TiO4, while the sample with 0.1% Mn2+ exhibited two bands, in the green and red spectral regions, assigned to Mn2+ ions at tetrahedral and octahedral sites. No emission was observed for the samples with 1.0% or 5.0% Mn2+. The excitation results for the sample with 0.1% Mn2+ ions showed characteristic peaks of Mn2+ transitions. Tanabe–Sugano theory was used to obtain the crystal field Dq, B, and C Racah parameters from the energy peak positions in the excitation spectrum of the sample with 0.1% Mn2+. Photoacoustic measurements revealed a broad band, characteristic of semiconductor materials, hiding the Mn2+ transitions.

The MgO-SiO 2 system with small quantities of MnCO 3 was produced by solid-state reaction at high temperature. The crystallographic phases and the amounts of components were determined by X-ray diffraction measurements. Emission and excitation spectra of samples with Mn replacing 1% and 5% of Mg in mass were obtained at room temperature. The photoluminescence spectra showed a broad band between 580 nm and 800 nm assigned to transitions of Mn 2+ in octahedral sites and a narrow emission at 610 nm, overlapped to the broad band, attributed to Mn 4+ ions in octahedral sites.

This work presents photoluminescence data for gallium-niobium oxide with chromium ion as an impurity. The samples were obtained by the solid-state method (SSM) and the wet-chemical method (WCM) and investigated by X-ray diffraction, photoluminescence, excitation, and photoacoustic and X-ray fluorescence. The color of the sample obtained by the SSM was pink, while the color of the sample prepared by the WCM was green. This dramatic difference was associated with Cr3+ concentration and with the neighborhood of the doping ions, obtained from crystallographic data, which is strongly dependent on the preparation method. The difference between the samples was also verified in the photoacoustic and excitation spectra, in which the energy bands were located at different energy levels; on the other hand, in the photoluminescence spectra, no band shift was observed. All spectra were assigned to chromium ions at nonequivalent octahedral sites.

In this work, the optical properties of the gallium–niobium oxide doped with chromium ions were investigated. The samples were obtained by wet chemical and solid-state methods, investigated by X-ray powder diffraction and the data were refined by Rietveld methods. The morphology was determined by scanning electron microscope (SEM) images. The photoluminescence, excitation and photoacoustic measurements showed broad and intense bands in the red region of the spectrum, associated with energy transitions of chromium ions in octahedral sites. From the optical spectra and using the crystal field theory, the energy parameters were obtained.

Metallic colloids can confine and focus light below the diffraction limit, leading to interesting properties and applications, such as metamaterials and sensors. However, accurate knowledge of the refractive indices of these colloids is critical to develop their unique optical properties. Anisotropic colloids, such those with Au nanorods (NRs) can be aligned with external electric fields, thus dynamically controlling the system's optical properties. NRs have two extinction peaks corresponding to plasmon resonances along and across the long NRs axis. By applying a variable voltage across the laser propagation direction, Padilha et al. measured the dependence of the extinction on this applied voltage and on the light polarization [1]. The sample's nonlinear refractive index n 2 was measured for applied voltages up to 10 kV and for laser polarization perpendicular and parallel to the applied electric field, obtaining a variation of ∼25% of the n2 value compared to when one does not apply any voltage.

We present the photoluminescence, excitation and photoacoustic spectra at room temperature of the system MgGa 2 O 4 –Ga 2 O 3 doped with Cr 3+ . The samples were prepared by solid state reaction and their formation was verified by X-ray diffraction. The emission spectra exhibit broad bands in the red and infrared regions associated to Cr 3+ with octahedral coordination. The excitation as well as the photoacoustic spectra show broad and intense bands in the visible region, all associated to Cr 3+ ions in octahedral sites, making this material interesting for future practical applications.

The etching rate of silica glass in 40% hydrofluoric acid under the influence of electric fields is studied with the help of an interferometric technique. A linear dependence of etching rate with field strength was found, with a $\ensuremath{\sim}2.5%$ etching rate change for an applied field of 20 MV/m. The experimental results are compared with those of a simple model that attributes this dependence to partial orientation of the HF molecules in the electric field. The measured dependence is sufficiently significant to account for the selective etching observed in frequency doubling glasses and fibers.

Erbium-doped fibers have been prepared for frequency doubling with various input powers. Annealing experiments were carried out, and a single exponential decay in time was found for the conversion efficiency. An activation energy of ~ 0.2 eV was measured for two fibers with different Er 3+ concentrations. A peculiar modal evolution was also observed in a scale of minutes.

The spatial distribution of the second-order nonlinearity induced in thermally poled Infrasil silica samples is recorded after thermal annealing experiments. Two regimes have been studied: short and long poling durations. For short poling durations, the observations are in good agreement with a model where only one ion type recombines inside the depletion region. The nonlinear distribution and erasure observed for the other case are well explained by considering the addition of another positive-charged ion injected during the poling process. This second ion acts as a barrier during thermal annealing and reduces the mobility of the first one.

In-fiber modulators are extremely attractive for telecommunication applications, and electro-thermal polin can be used to induce the necessary second-order nonlinearity in the glass fiber [1]. Long et al. have recently reported a way of mounting and poling D-fibers that is extensible to volume manufacturing and a relatively low voltage modulator has been demonstrated [2]. D-fibers are rugged, particularly if inbeded i a resin such as polyimide, but restrict the choice of available fibers, are not easily spliced, and a part of the voltage applied externally is wasted in biasing the cladding, unless further polishing/etching is used to remove the cladding and leave only the core region of the fiber. In the present work, we describe an alternative approach to making a fiber modulator, where pieces of conventional fiber are used, the central part of which is etched to the core and subsequently poled. After etching, the fibers have a diameter of ~10 μm and therefore are referred to as microfibers. Microfibers are surprisingly strong for their diameter and have some unique advantages. They can be fabricated with any fiber, the two ends that are not etched are truly easily spliceable, and the applied voltage during poling and in later use of the modulator develops mainly in the core, ensuring a large overlap integral.

Soft glasses, such as soda lime are the often used in waveguide fabrication by ion exchange. They are also cheap, readily available, and are potentially a base material for active components in fiber-to-the-home systems. Therefore, waveguide modulators based on poled soda lime glass are of great interest. In this work we demonstrate that it is possible to induce a large second-order optical nonlinearity in soda lime and borosilicate glass with the electro-thermal poling procedure described by Myers et al1. We also demonstrate a scheme based on poling to record single-mode waveguides in soda lime.

It is now generally believed that second harmonic generation in an optical fiber can be attributed to the creation of a permanent dc electric field grating along the fiber. The grating allows for quasi phase matching and gives rise to high conversion efficiencies. Imaging the grating with micrometer spatial resolution has so far been a difficult task because the cladding of the fiber shields efficiently the core from the environment. Indirect techniques have been employed, such as probing the small changes in the spontaneous Raman spectrum scattered as side-light1. Besides being of difficult interpretation, such technique gives low signal-to-noise ratio measurements.

The authors report experimental results on the optical limiting behavior of a bismuth oxide-based glass by exciting the samples with nanosecond laser pulses at 532 and 598 nm. The results show that two-photon and free-carrier absorption processes contribute for the nonlinear absorption. Values for beta, the two-photon absorption coefficient, and sigma_e, the absorption cross section due to free carriers, were determined. The values for beta and sigma_e are dependent on the amount of bismuth oxide in the glass composition.

Both the second-order nonlinear distribution and the built-in electric field have been measured in poled Infrasil™ silica samples, leading to the determination of the third-order nonlinear susceptibility spatial distribution. A difference between the χ(2) and electric field profiles has been observed in the first micrometers near the surface in contact with the anode. This behavior could be attributed to a modification of the χ(3) susceptibility in the poled region.