Nonlinear refractive index measurements in antimony-sulfide glass films using a single beam nonlinear image technique

The nonlinear refractive index, n(2), of films based on the new glass system Sb(2)O(3)-Sb(2)S(3) was measured at 1064 nm with laser pulses of 15 ps, using a single-beam nonlinear image technique in presence of a phase object. The films were prepared from bulk glasses by RF-sputtering. A large value of n(2) = 3 x 10-(15) m(2)/W, which is three orders of magnitude larger than for CS(2), was determined. The result shows the strong potential of antimony-sulfide glass films for integrated nonlinear optics. (c) 2005 Elsevier B.V. All rights reserved.

Study of the most suitable new glass laser to incorporate ytterbium: alkali niobium tellurite, lead fluorborate or heavy metal oxide

Diode-pumped Yb-doped glass lasers have received considerable attention for applications such as high-power beam production or femtosecond pulses generation. In this paper, we evaluate the laser potential of three different glass families doped with Yb3+ : alkali lead fluorborate (PbO-PbF2-B2O3), heavy metal oxide (Bi2O3-PbO-Ga2O3) and niobium tellurite (TeO2-Nb2O5-K2O-Li2O). Spectroscopic properties were studied for the samples and calculations of the minimum laser pump intensity (I-min), saturation fluence (U-sat) and the theoretical limit of peak power (P-max) are also presented. A comparison of laser properties of these three different glasses and their importance is shown and analyzed. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Laser weld: microstructure and corrosion study of Ag-Pd-Au-Cu alloy of the dental application

The laser Welding process was introduced into dentistry by the end of the 1980s, resulting on a great impulse to that area with the development of cheaper and smaller equipment, using simpler technique. This allowed greater use of that process on the confection of prostheses compared to the brazing process since the heat source for that process is a concentrated light beam of high power, which minimizes distortion problems on the prosthetic pieces. Ag-Pd-Au-Cu alloy used on the confection of dental implant prostheses was observed before and after subjection to the laser welding process. The microstructure was analyzed with the. use of optic microscopy and the corrosion resistance was studied by the traditional electrochemical techniques and by electrochemical impedance, under environmental conditions simulating the aggressiveness found in the mouth cavity. A structural change was detected on the weld area, which presented a refined microstructure deriving from the high-speed cooling. The base metal out of the weld area presented a fusion coarse microstructure. The electrochemical essays showed differences on the potentiodynamic polarization behavior in both weld and metal base areas, indicating superior corrosion resistance in the weld area. The impedance spectra were characterized by capacitive distorted components, presenting linear impedance in the low frequencies area. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Surgical treatment of ranula with carbon dioxide laser radiation

Ranula is a mucous extravasation cyst which appears as a swelling in the submental and submandibular regions. Several surgical techniques to manage ranula have been described in the literature, these techniques include the CO2 laser radiation excision. Four patients were treated for intraoral ranula in the floor of the mouth by marsupialization with carbon dioxide laser radiation with defocused beam, continuous mode and 4 watts of power. There were no complications and no recurrences have occurred to date. The results showed that carbon dioxide laser radiation gives optimal results with no need for suture and good wound healing.

Measurement of low-derivative surface lenses by two-laser holography with Bi12TiO20 crystals

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Design, construction, and performance of a real-time holographic refractometry prototype for liquid analysis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Enhanced multi-wavelength holographic profilometry by laser mode selection

The application of multi-wavelength holography for surface shape measurement is presented. In our holographic setup a Bi12TiO 20 (BTO) photorefractive crystal was the holographic recording medium and a multimode diode laser emitting in the red region was the light source in a two-wave mixing scheme. The holographic imaging with multimode lasers results in multiple holograms in the BTO. By employing such lasers the resulting holographic image appears covered of interference fringes corresponding to the object relief and the interferogram spatial frequency is proportional to the diode laser free spectral range (FSR). We used a Fabry-Perot étalon at the laser output for laser mode selection. Thus, larger effective values of the laser FSR were achieved, leading to higher-spatial frequency interferograms and therefore to more sensitive and accurate measurements. The quantitative evaluation of the interferograms was performed through the phase stepping technique (PST) and the phase map unwrapping was carried out through the Cellular-Automata method. For a given surface, shape measurements with different interferogram spatial frequencies were performed and compared, concerning measurement noise and visual inspection.

Laser stimulated light reflection for TeO2-WO 3-Bi2O3 thin films with incorporated Si nanoparticles

A novel method of preparation of the Si nanoparticles (NPs) incorporated in tellurite TeO2-WO3-Bi2O3 (TWB) thin films is proposed. This mew method applies RF magnetron sputtering technique at room temperature. The incorporation of Si NP was confirmed by transmission electron microscopy (TEM); isolated Si NPs with diameters of around 6 nm are observed. Energy dispersive X-ray spectroscopy (EDS) was performed during TEM analysis in order to confirm the presence of Si NP and also the other elements of the thin film. The thin films are explored with respect to the photoinduced changes of the reflectivity within the 400-65 nm spectra range using a 10 ns pulsed Nd:YAG with power densities varying up to 400 MW/cm2 and beam diameter within the 3-5 mm range. The observed processes are analyzed within a framework of trapping level conceptions for the Si NP. The possible application of the discovered materials as optical sensitive sensors is proposed. © 2013 Elsevier B.V.

Tamanho de gotas de pontas de pulverização em diferentes condições operacionais por meio da técnica de difração do raio laser

The present study aimed to evaluate the droplet spectrum of hydraulic nozzles, under different pressures and spray liquid compositions, using a laser particle size analyzer. In a completely randomized design, two air induction twin flat-fan nozzles (AD-IA/D 11002 and AD-IA/D11004) and two hollow-cone nozzles (MAG - 2 and MAG - 4) were evaluated, in factorial design 3 x 2: tree spray pressures (207, 276 and 345 kPa for twin flat-fan nozzles, and 414, 483 and 552 kPa for cone nozzles); and two spray liquid compositions (water and water plus phosphatydilcoline + propionic acid adjuvant). The addition of adjuvant reduced the volume median diameter for the AD-IA/D 11002 and 11004 nozzles; however it had an opposite effect with the MAG - 4 nozzles and not changed with the MAG - 2 nozzles. In adverse weather conditions, it is not recommended the use of hollow cone spray nozzle, even with the addition of adjuvant tested because of the high risk potential of drift.

Influência da potência de laser Nd: YAG na soldagem do aço inoxidável duplex UNS S32205

Pós-graduação em Engenharia Mecânica - FEIS

Lensometry by two-laser holography with photorefractive Bi12TiO20

Refractive and profilometric measurements of lenses were performed through holography with a photorefractive Bi12TiO20 crystal as the recording medium. Two properly aligned diode lasers emitting in the red region were employed as light sources. Both lasers were tuned in order to provide millimetric and sub-millimetric synthetic wavelengths. The surfaces of the test lens were covered by a 25-μm opaque plastic tape in order to allow the lens profilometry upon illuminating them with a collimated beam. The resulting holographic images appear covered by interference fringes corresponding to the wavefront geometry of the wave scattered by the lens. For refractive index measurement a diffusely scattering flat surface was positioned behind the uncovered lens which was also illuminated by a plane wave. The resulting contour interferogram describes the form of the wavefront after the beam traveled back and forth through the lens. The fringe quantitative evaluation was carried out through the four-stepping technique and the resulting phase map and the Branch-cut method was employed for phase unwrapping. The only non-optical procedure for lens characterization was the thickness measurement, made by a dial caliper. Exact ray tracing calculation was performed in order to establish a relation between the output wavefront geometry and the lens parameters like radii of curvature, thickness and refractive index. By quantitatively comparing the theoretical wavefront geometry with the experimental results relative uncertainties bellow 3% for refractive index and 1 % for focal length were obtained. © 2008 American Institute of Physics.

Influência do espaçamento do feixe de laser Nd: YAG na obtenção de óxidos e nitretos na superfície do titânio em pressão atmosférica

Neste trabalho investigou-se a modificação de superfície do titânio pela irradiação com feixe de Laser Nd:YAG. Os parâmetros do laser como a potência, o comprimento de onda, a frequência, a velocidade de varredura e a área de exposição foram mantidos constantes, exceto o espaçamento da matriz, o qual foi de 0,01 e 0,02 mm. A caracterização da superfície foi realizada por Microscopia Eletrônica de Varredura (MEV) e Difração de Raios X (DRX), sendo que os espectros foram refinados pelo método Rietveld. Pela análise de MEV, observou-se uma mudança na topografia, obtendo uma superfície rugosa produzida pelo fenômeno de ablação. As análises por Rietveld dos espectros de difração de raios X detectaram TiN, Ti2N, TiO2 (anatásio e rutilo), sendo que a amostra com espaçamento 0,01 mm apresentou uma maior quantidade de óxidos e nitretos. Isso pode ser devido à sobreposição do feixe, induzindo à formação de uma superfície com maior estabilidade termodinâmica. Os óxidos e nitretos obtidos são de grande importância, pois são responsáveis por produzir uma maior interação entre o osso-implante.