Articolele autorului Adrian RIZEA
Link la profilul stiintific al lui Adrian RIZEA

Femtosecond laser ablation of TiO2 films for two-dimensional photonic crystals

Femtosecond laser ablation of TiO2 thin films was studied as a function of laser pulse energy and number of pulses. The ablated holes were characterized by atomic force microscopy and the optimum irradiation conditions were chosen for producing a periodic structure of triangular lattice of air holes in the TiO2 films. A photonic structure with period of 1.5 μm was designed to show photonic band gap in the near-infrared, at the telecommunication

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Interferential dichroic filter

The aim of the present paper is to provide a description of the general aspects regarding the theoretical concept, the structure, the execution and the properties of an interferential filter used in a medical application. The main functional characteristic of this filter is to block the radiation supplied by a He-Ne laser ( = 632,8 nm), allowing to passing only the higher wavelength radiation ( > 650 nm). The most important problem that has

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Selective interferential filters with high optical efficiency and increased resistance in intense optical radiation

In this paper the results of a study and the found solutions for some interferential filters obtained through Physical Vapor Deposition method on optical support are presented. These filters have a good resistance to an intense optical radiation, as well a high optical efficiency in a large spectral domain (400 - 2000 nm). Both theoretical and experimental aspects will be discussed herein.

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Ellipsometric arrangement for thin films control

An ellipsometric experimental set up of PSA type with an extinction factor E.F.= 10-5, inspired from the Gaertner’s L119 and a powerful BASIC software for the theoretical calculus of the ellipsometric parameters  and , including original practical solutions, were developed. Encouraging results were obtained in applying the simple ellipsometric method of azimuths to determine the optical constants: refractive index n, absorption index k and

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Effect of pulse number on the ablation rate of metals in PLA multi-pulse regime

The pulsed laser ablation of aluminium, copper and titanium irradiated with 4.5 ns pulses at 355 nm, 532 nm and 1064 nm wavelengths is investigated in open air at normal atmospheric conditions. The effect of pulse number, which is varied in the range of 5 to 50, on ablation rate in these three wavelength regimes is determined. The results indicate a higher efficiency of the ablation in VIS and UV regimes as compared to IR regime which is characterised

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Two-dimensional photonic crystals produced by femtosecond laser ablation on TiO2 films
Angle-resolved evanescent-wave cavity ring-down spectroscopy for thin film-solid interface characterization

A new method, that involves Evanescent-Wave Cavity Ring-Down Spectroscopy (EW-CRDS), is presented. This method is useful for the study of thin films on optical solid surfaces. The new design of experimental set-up incorporates a semicylindrical prism with a plane surface where the Total Internal Reflection (TIR) effect appears. The antireflex (AR) coated cylindrical surface of the prism induces the stability of resonant cavity. The evanescent wave

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Antireflection optical coatings for the visible spectral range

In this paper, a design for a reliable antireflection coating is proposed. This is, probably, among the best combinations of a maximum imposed number of six layers for an antireflection coating, having a very good efficiency, a good reproducibility and a durable coating package. The applications refer to visible spectral range, widely ordered in optical industry.

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Design technique for all-dielectric non-polarizing beam splitter plate

There are many situations when, for the proper working, an opto−electronic device requiring optical components does not change the polarization state of light after a reflection, splitting or filtering. In this paper, a design for a non−polarizing beam splitter plate is proposed. Based on certain optical properties of homogeneous dielectric materials we will establish a relia− ble thin film package formula, excellent for the start of optimization

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Design techniques for all-dielectric polarizing beam splitter cubes, under constrained situations

In this paper, a guide to design optical coatings for polarizing beam splitter cubes, starting from certain imposed situations, is presented. For this purpose, will be presented two main situations: the criterion by which we choose materials for interferential package if the glass prisms is imposed and, on the other hand, how to choose the glass for prisms, depending on the materials for interferential package that we need to build.

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