Biomechanical model produced from light-activated dental composite resins: a holographic analysis

Light-activated dental composites, commonly applied in dentistry, can be used as excellent material for producing biomechanical models. They can be cast in almost any shape in an appropriate silicone mold and quickly solidified by irradiation with light in the blue part of the spectrum. In that way, it is possible to obtain any number of nearly identical casts. The models can be used to study the behavior of arbitrary structure under mechanical loads. To test the technique, a simple mechanical model of the tooth with a mesio-occluso-distal cavity was manufactured. Composite resin restoration was placed inside the cavity and light cured. Real-time holographic interferometry was used to analyze the contraction of the composite resin and its effect on the surrounding material. The results obtained in the holographic experiment were in good agreement with those obtained using the finite element method.3rd International Conference on the Physics of Optical Materials and Devices, Sep 02-06, 2012, Belgrade, Serbi

Inducing subwavelength periodic nanostructures on multilayer NiPd thin film by low-fluence femtosecond laser beam

During femtosecond interaction with surfaces, the processes of liquid and solid-state dewetting could be responsible for the generation and regrouping of nanoparticles and nanoparticle clusters. The occurrence of surface plasmon polariton most probably induces the LIPSS arrangement. We have used low-fluence scanning femtosecond beam to generate sub-wavelength periodic structures on multilayer Ni/Pd thin films on Si. The spatial period of LIPSS increases with the change of scanning directions in respect to the polarization direction due to the phase difference increase between the incoming and induced oscillations. (c) 2017 Elsevier B.V. All rights reserved.10th International Conference on Photo-Excited Processes and Applications (ICPEPA), Aug 29-Sep 02, 2016, Transilvania Univ Brasov, Brasov, Romani

Light propagation in quasi-periodic Fibonacci waveguide arrays

We investigate light propagation along one-dimensional quasi-periodic Fibonacci waveguide array optically induced in Fe:LiNbO3 crystal. Two Fibonacci elements, A and B, are used as a separation between waveguides. We demonstrate numerically and experimentally that a beam expansion in such arrays is effectively reduced compared to the periodic ones, without changing beam expansion scaling law. The influence of refractive index variation on the beam expansion in such systems is discussed: more pronounced diffraction suppression is observed for a higher refractive index variation

Laser-induced structural and composition modification of multilayered Ni/Ti thin film in air and liquids

The interaction of an Er, Yb, Cr-glass laser, operating at 1540 nm wavelength and a pulse duration of 40 ns, with Ni/Ti multilayer thin films has been studied. Five (Ni/Ti) bilayers deposited by DC ion sputtering on Si(100) wafers to a total thickness of about 180 nm were treated with laser fluences of about 6.4 and 8.8 J cm(-2). Single and multi-pulse laser irradiation was done at normal incidence in air, water and ethanol ambients. The composition and surface morphology were monitored by particle-induced x-ray emission, Rutherford backscattering spectrometry (RBS), scanning electron microscopy and profilometry. Most of the absorbed laser energy was rapidly transformed into heat, producing intensive modifications of composition and morphology on the target surface. The results show an increase in surface roughness, formation of parallel periodic surface structures, appearance of hydrodynamic features and ablation of surface material. RBS analysis revealed that laser modification induced inter-mixing between the components of individual Ni and Ti layers, with indications of the formation of NiTi intermetallic compounds. An interesting finding is the morphological changes dominant in the Si substrate, whereas the Ni/Ti multilayer structure has mainly undergone changes in the chemical composition