Simultaneous Determination Of Refractive Index Research Articles

Simultaneous Determination of Refractive Index and Thickness of Submicron Optical Polymer Films from Transmission Spectra.

High-transparency polymers, called optical polymers (OPs), are used in many thin-film devices, for which the knowledge of film thickness (h) and refractive index (n) is generally required. Spectrophotometry is a cost-effective, simple and fast non-destructive method often used to determine these parameters simultaneously, but its application is limited to films where h > 500 nm. Here, a simple spectrophotometric method is reported to obtain simultaneously the n and h of a sub-micron OP film (down to values of a few tenths of a nm) from its transmission spectrum. The method is valid for any OP where the n dispersion curve follows a two-coefficient Cauchy function and complies with a certain equation involving n at two different wavelengths. Remarkably, such an equation is determined through the analysis of n data for a wide set of commercial OPs, and its general validity is demonstrated. Films of various OPs (pristine or doped with fluorescent compounds), typically used in applications such as thin-film organic lasers, are prepared, and n and h are simultaneously determined with the proposed procedure. The success of the method is confirmed with variable-angle spectroscopic ellipsometry.

Ellipsometric study of molecular orientations of Thermomyces lanuginosus lipase at the air–water interface by simultaneous determination of refractive index and thickness

Ellipsometric studies of very thin organic films suffer from the low refractive index contrast between layer and bulk substrate. We demonstrate that null ellipsometry can not only provide detailed information about the adsorption kinetics and surface excess values, but in addition on layer thicknesses with submonolayer resolution of a lipase from Thermomyces lanuginosus at the air–water interface. While measuring very close to the Brewster angle, refractive indices and layer-thicknesses can both be determined with a precision that is sufficiently high to make conclusions on the density and orientation of the molecules at the interface. The orientation was found to be concentration- and pH value-dependent. At the isoelectric point, the lipase was almost vertically oriented with respect to the surface, while for pure distilled water and low lipase concentration a rather horizontal alignment was found. Further experiments, varying the size of the interfacial area in a Langmuir trough, confirm the different layer structures.

Simultaneous determination of refractive index and thickness of moderately thick plane-parallel transparent glass plates using cyclic path optical configuration setup and a lateral shearing interferometer

We present a simple technique for simultaneous determination of refractive index and thickness of moderately thick plane-parallel transparent glass plates (GPs) using a cyclic path optical configuration (CPOC) setup and a wedge shear plate as lateral shearing interferometer. The CPOC setup is used to simultaneously focus the counterpropagating converging beams at a common point at its hypotenuse arm. The apparent thickness and real thickness of the test GP are determined by observing three retrocollimation positions of the GP surfaces with respect to the common focus point. The RI is obtained by dividing the real thickness with apparent thickness of the GP. Presented in this paper are the results obtained for a test GP with a thickness of 14.983 mm and a RI of 1.515.

Determination of refractive index, thickness, and the optical losses of thin films from prism-film coupling measurements

We present a method of analysis of prism-film coupler spectroscopy based on the use of transfer matrix and genetic algorithm, which allows the simultaneous determination of refractive index, thickness, and optical losses of the measured layer.

Simultaneous determination of refractive index and thickness of multilayer dielectric films by discrete Fourier transform

In this work a novel method is proposed for simultaneous determination of refractive index n and geometrical thickness d. Transmittance spectra of dielectric films, exhibiting weakly absorbance in 14,285–14,492 cm −1 region, were exposed to Discrete Fourier Transform (DFT) whereby { n, d} values were extracted at the same time. Refractive index variation of films is assumed to be constant in the measurement range. Obtained results revealed favourable accordance with the literature and mechanical micrometer readings.

Simultaneous determination of refractive index, extinction coefficient, and void distribution of titanium dioxide thin film by optical methods

The refractive index n(λ) and the extinction coefficient k(λ) of a TiO(2) film prepared by electron-beam evaporation are determined in the spectral region 1.5-5.5 eV. The transmission spectrum of the TiO(2) film on a vitreous silica specimen is inverted to get the k(λ) of TiO(2) in its interband transition region. Above 3.5 eV, k(λ) is used to get the coefficients of the quantum mechanically derived dispersion relation of an amorphous TiO(2). These coefficients and n(∞) are used to determine n(λ). The modeling procedure is applied to spectroscopic ellipsometry data of a TiO(2) film on a c-Si specimen, and the void distribution of the film is revealed. With spectroscopic ellipsometry data above the fundamental band gap, valuable information about surface roughness is obtained. The effective thickness of this rough surface layer is confirmed by an atomic force microscopy measurement.

A New Kösters Prism Interferometer for Simultaneous Determination of Refractive Index and Thermal Expansion of Crystals as a Function of Temperature

An uniquely-modified Kosters prism interferometer for the simultaneous and independent measurement of refractive index, δn(T), and thermal expansion, δl(T), as a function of temperature in the range 308-1273 K, is described. The capabilities of the system are demonstrated via measurement of δn(T) and δl(T) along both the [100] and [001] directions up to and through the α-8 phase transition in quartz, with results in good agreement with previous measurements. Further to this, experiments to determine δn(T) and δn(T) along the [100], [010] and [001] directions in the orthorhombic nonlinear optical crystal indium-doped KTiOAsO 4 are described. The results are used to show that the ferroelectric-paralectric phase transition at T c =1063 K is second-order and exhibits Landau-type behaviour over a range of 100 K below T c . Finally, similar experiments on the orthorhombic crystal Ba 2 NaNb 5 O 15 are reported. The behaviours of δn(T) and δl(T) at the ferroelastic phase transition at 563 K and the ferroelectric-paraelectric phase transition at T c = 849 K are discussed. Clear evidence of the existence of polar fluctuations in the paraelectric phase is presented.

Laser Method of Refractive Index Determination Within the Selective Reflection Band of Cholesteric Liquid Crystals

Abstract A principally new method of simultaneous determination of refractive index and small values of helical pitch of cholesteric liquid crystals is proposed. Its accuracy, limitations and possible use are also discussed.

Simultaneous determination of refractive index and absorbance spectra of chemical samples using surface plasmon resonance

A technique for using surface plasmon resonance to characterize dispersive refractive-index and absorption profiles is reported. This is accomplished by simultaneously exciting surface plasmon resonance at multiple angles and multiple wavelengths and then analyzing the resulting resonance profiles. By calibrating with liquids of known refractive index profiles, the refractive index spectrium of solid or liquid samples can be measured. Preliminary experimental results demonstrate a refractive index sensitivity of 6 × 10 −4 between 580 and 700 nm for refractive indices from 1.3 to 1.5.

Simultaneous Determination of Refractive Index and Density of an Evaporating Aqueous Solution Droplet

The experimental technique and computational method developed for simultaneous determination of refractive index and density of an electrolyte solution droplet undergoing evaporation at 25°C are described. Results are presented for the systems (NH4)2SO4-H2O, Na2SO4-H2O, and NaNO3-H2O over a wide concentration range from high dilution to critical supersaturation. It is shown that the partial molal refraction derived for each electrolyte is remarkably constant throughout the entire concentration region, thereby validating the partial molal refraction approach for predicting the refractive index of highly supersaturated solutions.

Simultaneous determination of refractive index, its dispersion and depth-profile of magnesium oxide thin film by spectroscopic ellipsometry

A new method of using the spectroscopic ellipsometry technique to determine (a) the true (or bulk) refractive index of the film material, (b) the dispersion of the above refractive index with wavelength, (c) the thickness of the film, and (d) the distribution of the voids in the film is presented.

Simultaneous determination of refractive index and size of spherical dielectric particles from light scattering data

The diameter and refractive index of micrometer sized spherical dielectric particles are simultaneously deduced using the wavelength dependence of backscattering data from optically levitated particles. The accuracy of the results is set by experimental errors in the determination of the wavelength of backscatter resonance peaks and the ratio of slopes of specified peaks. At present the refractive index and diameter can be deduced with relative errors of 5 x 10(-5). This represents the most accurate determination of absolute size and refractive index yet made by light scattering. A reduction of these errors by an order of magnitude is possible. We assume a priori knowledge of diameter and refractive index with accuracy of 10(-1) and 5 x 10(-3), respectively.

Stepped Interference Reflector for Determining the Optical Constants of Nonabsorbing Unimolecular Films I Theory

An interference reflector consisting of two barium stearate steps (~1000 A and 2000 A in height) on chromium, has been devised as the basis of a simple method for the simultaneous determination of refractive index (n2) and thickness (d2) of nonabsorbing unimolecular films. The measured variables are the two interference fringe displacements produced when an unknown film is cast simultaneously over both steps. From these fringe shifts, n2 and d2 may be calculated easily by the use of approximations good to three significant figures. The method is sensitive enough to determine n2 to within 1% and d2 to within 4% for films ⩾20 A in thickness. Measurements and computations for an unknown film may be completed in under 2 hr. Experimental verification is in a separate paper.