Alexandre R. Camara

Study of thermally poled fibers with a two-dimensional model

A two-dimensional (2D) numerical model is implemented to describe the movement of ions under thermal poling for the specific case of optical fibers. Three types of cations are considered (representing Na(+), Li(+) and H3O(+)) of different mobility values. A cross-sectional map of the carrier concentration is obtained as a function of time. The role of the various cations is investigated. The assumptions of the model are validated by comparing the predictions to experimental data of the time evolution of the nonlinearity induced. A variational analysis of poling parameters including temperature, poling voltage, sign of the bias potential and initial ionic concentrations is performed for a particular fiber geometry. The analysis allows identifying the impact of these parameters on the induced second-order nonlinearity in poled fibers.

Microsecond switching of plasmonic nanorods in an all-fiber optofluidic component

As information technologies move from electron-to photon-based systems, the need to rapidly modulate light is of paramount importance. Here, we study the evolution of the electric-field-induced ali ...

Optical creation and erasure of the linear electrooptical effect in silica fiber

We study the creation and erasure of the linear electrooptical effect in silicate fibers by optical poling. Carriers are released by exposure to green light and displaced with simultaneous application of an internal dc field. The second order nonlinear coefficient induced grows with poling bias. The field recorded (~10⁸ V/m) is comparable to that obtained through classical thermal poling of fibers. In the regime studied here, the second-order nonlinearity induced (~0.06 pm/V) is limited by the field applied during poling (1.2 × 10⁸ V/m). Optical erasure with high-power green light alone is very efficient. The dynamics of the writing and erasing process is discussed, and the two dimensional (2D) field distribution across the fiber is simulated.

Optical and Structural Properties of Zn2TiO4:Mn2+

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.

Photonics with Special Optical Fibers and Nanoparticles

Optical properties of nanorods in the presence of external electric field when confined to a special optical fiber was investigated, showing an increase of the longitudinal absorption peak in the presence of the field.

Pockels fibers by optical poling

Silica fibers with internal electrodes biased with HV are poled when simultaneously excited by green light. The x(2) induced measured through the Pockels effect at 1.55 μm reaches ~0.11 pm/V. Polin ...

Dengue Immunoassay using an LSPR-based Fiber Optic Sensor with Au Nanoparticles

An all-optical fiber sensor based on Localized Surface Plasmon Resonance (LSPR) and specular reflection from gold nanoparticles (NPs) has been functionalized detecting NS1 protein of dengue virus.