Thiago Alexandre Alves de Assumpção

O artigo apresenta a dinâmica do processo contínuo de imersão a quente no revestimento de tiras de aço por liga de alumínio e zinco, baseado no processo da linha Dual Purpose da Companhia Siderúrgica Nacional (CSN), licenciada pela BIEC International Inc. para utilização da liga 55% Al-Zn (denominada Galvalume®) no tratamento superficial de aços. São descritos brevemente todas as etapas desse processo, os equipamentos utilizados e como eles atuam para manter o fluxo contínuo, dando ênfase à importante atuação do inversor de frequência que controla a rotação e torque dos motores devido à alteração do raio da bobina quando ela está sendo enrolada e desenrolada. É apresentada também uma dedução matemática para as equações do torque e da rotação em função do número de ciclos efetuados pelo bobinador.

In this paper we present the fabrication and characterization of pedestal-type optical waveguides using aluminum nitride (AlN) as core layer. To the best knowledge of the authors, the utilization of AlN as core layer in pedestal-type waveguides has not been studied. The AlN thin films were obtained by radio frequency reactive magnetron sputtering from a pure aluminum target. The AlN refractive index was determined by ellipsometry. The optical waveguides were fabricated by the pedestal technique, which consists in etching the silicon oxide lower cladding layer before depositing the core layer. Thus, the waveguide geometrical definition is simplified because etching the AlN core is not necessary. AlN thin films of 0.6, 1, and 1.2 μm thick were deposited on thermally grown silicon dioxide using crystalline silicon (100) as substrate. The pedestal profile was defined using conventional photolithography, followed by plasma etching of the cladding layer. Optical propagation losses were measured for pedestal heights of 1 μm and widths from 1 to 100 μm.

This work explores the production and characterization of pedestal-type active waveguides based on PbO–GeO₂ (PGO) thin films codoped with Tm³⁺/Yb³⁺ rare earth ions. Silicon wafers containing around 1.7 μm of SiO₂ thickness were used as substrate, and the pedestal structure was obtained by conventional photolithography and plasma etching in a reactive ion etching reactor. Plasma etching procedures were made in steps to reduce roughness at the laterals and sidewalls of waveguides. Around 0.5 μm of Tm³⁺/Yb³⁺ codoped PGO thin film was obtained by radio frequency magnetron sputtering deposition after etching procedures. Results of scanning electron microscopy confirmed the waveguide pedestal profile. Optical propagation losses around 4, 5, and 20 dB/cm were observed at 1050, 633, and 543 nm, respectively, for waveguide width in the 30–100 μm range. Near field profiles at these wavelengths and also at 980 nm are also reported and confirmed the multimode coupling behavior. The present results corroborate the possibility of using Tm³⁺/Yb³⁺ codoped PGO thin films as active waveguides for photonic applications.