Papers by Keyword: Refractive Index

Abstract: Ellipsometry is a non-destructive and indirect technique able to characterize both optical and dielectric properties of thin films and bulks, besides determining the thickness of thin films. This characterization is performed by evaluating the change in the polarization state of the incident light when it interacts with the material of interest. In this work, the ellipsometry technique was used to characterize optical properties of AZ31 magnesium alloy samples. This alloy has several interesting properties such as low density, high thermal conductivity, good machinability, among others, which makes it suitable for use in automotive and aerospace components. However, when this alloy is exposed to ambient atmosphere, it undergoes natural oxidation, developing a surface film of oxides and/or hydroxides. This study aimed to establish an efficient methodology for accessing the optical and dielectric characteristics of the substrate (AZ31 alloy) as well as those for the surface film of oxide/hydroxides, and to obtain the thickness of this film. Four samples mechanically grinded and polished were investigated: One sample, namely P sample, was subjected to the ellipsometric measurements immediately after grinding and polishing and three samples, namely A10, A50 and A60, were exposed to the air at 150°C during 10, 50 e 60 minutes, respectively. From the results of the ellipsometric measurements for P sample, it was possible to determine the refractive index (n) and extinction coefficient (k) curves as a function of the wavelength (λ) for the substrate (AZ31 alloy). Besides, through appropriate modeling, it was possible to determine the thicknesses of the oxides/hydroxides films presented in A10, A50 and A60 samples. The thicknesses values obtained seem to be quite coherent when we analyze the surface roughness of these samples using the confocal microscope, validating the optical model constructed to represent the A10, A50 and A60 samples. The results achieved in this study can contribute to the study of both of oxides/hydroxides layers growth and protective coating films growth for AZ31 magnesium alloy.

Abstract: A glass series with chemical composition of {[(TeO₂)_0.7(B₂O₃)_0.3]_0.7(ZnO)_0.3}_1-x (La NPs)_x where x = 0.01, 0.02, 0.03, 0.04 and 0.05 molar fraction was synthesized through conventional melt-quenching method. The fabricated glasses were characterized by using UV-Vis and FTIR technique in the range of 220 to 800 nm and 280 to 2000 cm^-1 respectively. Various absorption bands that were recorded in FTIR spectra indicates the presence of TeO₄, BO₃ and BO₄ unit. In this research, indirect energy band gap showed an increasing trend while refractive index values decreases as amount of La NPs increases due to the decrement of high polarizability nonbridging oxygen number in the glass system. Other optical parameter that also take part in governing the value of refractive index such as electronic polarizability was also determined.

Abstract: Silica borotellurite glasses doped with manganese oxide with chemical formula {[(TeO₂)_0.7(B₂O₃)_0.3­]_0.8[SiO₂]_0.2}_1-x{MnO₂}_x (where x = 0.0, 0.01, 0.02, 0.03, 0.04 and 0.05 molar fraction) were fabricated. Silica were extracted from the burning process of rice husk. Glass samples were prepared by using the melt-quenching technique. The FTIR spectra showed that the addition of MnO₂ contributed to the transformation of TeO₄ to TeO₃. The diffraction pattern of XRD showed a broad hump which indicates the amorphous nature of the samples. The result for both optical band gap and Urbach energy showed decreasing trend as the concentration of manganese increased.

Abstract: We propose a new approach for determining the distribution of full-field refractive index based on the angle deviation method (ADM) with a surface plasmon resonance (SPR) sensor in phase detection. The inhomogeneous distribution of refractive index causes the variant deviation angles in the test light. SPR sensor is a sensitive angular sensor especially for phase detection. For the full–field phase measurement, we should use the four-step phase shift interferometry (PSI) to measure the phase shift profile of the test light after reflected from the SPR sensor. Thus the phase shift is caused by the variation of the refractive index. The approach can plot the full-field refractive index distribution in a short time and its resolution can be better than 2.2×10^-8 (RIU).

Abstract: The relationship between structure and refractive index for SiO₂-B₂O₃- Ta₂O₅-ZrO₂-Na₂O system glasses was investigated via Raman spectrum and V-block technology. The results showed that refractive index of the borosilicate glasses is mainly influenced by network structure such as planar [BO₃] triangle, [BO₄] tetrahedron and [SiO₄] tetrahedron. Refractive index decreases from 1.629 to 1.616 when B₂O₃ content increases from 15 mol% to 50 mol%. Na₂O component has a strong preference to provide non-bridging oxygen (NBO) atoms, which not only promotes the conversion of [BO₃] to [BO₄] unit but also depolymerizes the network structure. The refractive index has the highest value, =1.6264, when Na₂O content reaches to 28 mol%. Both ZrO₂ and Ta₂O₅ can promote structure formation of borosilicate glasses and make higher connection degree. However, the refractive index increasing with Ta₂O₅ addition is quicker than that with ZrO₂ addition.

Abstract: The spectra of refractive index and absorption coefficient in thin films of Ge_23.5Pb₂₀S_56.5 glassy system were calculated on the base of analysis of transmission spectra. The refractive index has values between 2.0 and 2.6 in the spectral range between 500 nm and 1200 nm. The existence of indirect allowed transitions with energy E_g = 1.70 ± 0.01 eV and phonon energy of w_ph= 0.11 eV at room temperature was found. For values of the absorption coefficient a < 10³см ^–1 the fundamental absorption edge is described by exponential function known as Urbach-rule. The static structure disorder parameter w_o, is equal to 0.06 eV.

Abstract: Static dielectric constant (ε₀) and refractive index (n) have been experimentally determined for binary liquid mixture of n-Hexanol (HxOH) with Acetophenone (ACP) over the entire concentration range of mixture composition (0.0 →1.0) at constant temperature 303.15 K. Static dielectric constant (ε₀) and refractive index (n) for the binary mixture have been measured using high precision LCR meter (0.2 MHz) and Abbe’s refractometer respectively. Excess of static dielectric constant (ε₀)^E and refractive index (n)^E are determined and fitted with Redlich-Kister polynomial equation to derive the binary coefficients and standard deviations. Deviations of these parameters are discussed in terms of terms of molecular interaction between the constituent species. In the present work, comparative study of various mixing models for static dielectric constant (ε₀) [Böttcher-Bordewijk (BOTT), Bruggeman (BRUG), Kraszewski (KRAZ), Looyenga (LOOY), Peon–Iglesias (P-I)] and for refractive index (n) [Oster (OST), Weiner (W), Eykman (EYK), Lorentz–Lorentz (L-L), Arago–Biot (A-G), Newton (Nw), Gladstone–Dale (G-D) and Erying–John (EJ)] have been carried out and their validity has been tested for the (n-HxOH+ACP) binary mixtures. The objective of the present work is to report the influence of nonassociative molecule on the molecular dynamics of associative molecules and validation mixing models.

Abstract: Studies on Physico-chemical properties of binary liquid mixtures provide information on the nature of interactions between the constituent of the binaries. Literature provides extensive data on the static dielectric constant (ε₀) and refractive index (n) of liquid compounds, but the combined study of all is quite scarce. In the present work static dielectric constant (ε₀) and refractive index (n) have been experimentally determined for binary liquid mixture of 1-Propanol (PrOH) with Acetophenone (ACP) over the entire concentration range of mixture composition (0.0 →1.0) at constant temperature 303 K. Static dielectric constant (ε₀) and refractive index (n) for the binary mixture have been measured using high precision LCR meter (0.2 MHz) and Abbe’s refractometer respectively. Excess of static dielectric constant (ε₀)^E and refractive index (n)^E are determined and fitted with Redlich-Kister polynomial equation to derive the binary coefficients and standard deviations. For interaction and structural information various parameters namely, Kirkwood correlation factor (g), Kirkwood effective correlation factor (g^eff), Kirkwood angular correlation factor (g_F) and Bruggeman parameter (f_B) are determined for the binary mixtures. Variations of these parameters against the concentration of constituents are discussed in terms of molecular interaction between the constituent species.

Abstract: This paper presents the optical properties of erbium doped tellurite glasses with the composition of 55TeO₂-2Bi₂O₃-35ZnO-5PbO-(3-x)Na₂O-xEr₂O₃ where x = 0, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mol% . Refractive index of the glasses was measured using Brewster’s angle method and their optical absorption spectra were measured in spectral range 200 – 1100 nm recorded at room temperature. The results show that the glass refractive index increases with the increase of Er³⁺ ion content in the glass and the optical band gap energy decreases with the increase of erbium content in the glass.

Abstract: The influence of process parameters on amorphous reactively sputtered silicon nitride thin films is reported in this study. The films were prepared with various argon and nitrogen flows, and sputter power in in-line horizontal coater by DC magnetron reactive sputtering from Si (10% Al) target. Refractive index and mechanical properties like residual stress, hardness and elastic modulus were studied. We show that process pressure has an important influence on mechanical properties of the sputtered film. On the other hand, the nitrogen content is the key factor for the optical properties of the films.