Spectrogoniometric determination of refractive indices of GaSe

A simple interference spectroscopy technique of determining real parts of refractive indices in thin isotropic or anisotropic films is presented. This method is based on the evaluation of the orders of extrema in interference spectra of optical transmittance and/or reflectance measured for various angles of light incidence. It also makes possible to determine thickness of the investigated sample. This method of investigations was used to determine the parameters of gallium selenide (GaSe). The determined spectral characteristics of ordinary and extraordinary refractive indices of GaSe are compared with the data presented in literature by other authors.     

Measurement of refractive indices of prismatic materials

The purpose of this work is to describe the advantages of a simple alternative to the minimum-deviation and other methods used to determine refractive indices of prism-shaped specimens.     

Double slit interferometry to measure the EUV refractive indices of solids using high harmonics

Accurate values of the extreme ultraviolet (EUV) optical properties of materials are required to make EUV optics such as filters and multilayer mirrors. The optical properties of aluminum studied in this report are required, in particular, as aluminum is used as an EUV filter material. The complex refractive index of solid aluminum and the imaginary part of the refractive index of solid iron between 17 eV and 39 eV have been measured using EUV harmonics produced from an 800 nm laser focused to 10(14) Wcm(2) in an argon gas jet impinging on a double slit interferometer.     

Determination of refractive indices of opaque rough surfaces

The refractive indices of optical materials are usually determined from spectrophotometric and ellipsometric measurements of specular beams. When the roughness of the interfaces increases, the energy in the specularly reflected and transmitted beams decreases and scattering becomes predominant. For strong roughness (compared to the incident wavelength) a surface does not exhibit specular reflection or transmission, making difficult the determination of the refractive index. We describe two techniques, based on scattering measurements, that one can use to determine the refractive indices of opaque inhomogeneous media.     

More on the accurate measurement of refractive indices

Measurement of refractive indices using the normalincidenceprocedure and its relationship to the general andminimum deviation method are described.     

Determining mean integral refractive indices in geodetic rangefinding

Translated from Izmeritel'naya Tekhnika, No. 10, pp. 17–18, October, 1990.     

Silica nanorod-array films with very low refractive indices

The refractive-index contrast is an important figure of merit for dielectric multilayer structures, optical resonators, and photonic crystals. This represents a strong driving force for novel materials that have refractive indices lower than those of conventional optically transparent materials. Silica nanorod-array dielectric films with unprecedented low refractive indices of 1.08 are demonstrated and shown to have viable optical properties including enhanced reflectivity of a single-pair distributed Bragg reflector.     

Scattering by particles with radially variable refractive indices

The problem of scattering by a spherical particle whose refractive index arbitrarily depends on the distance from its center has been solved. A computational scheme for determining the scattering coefficients for the refractive-index profiles given by some piecewise smooth function is constructed, and the models to use it are presented. The simple algorithm for evaluating the scattered and internal field vectors is elaborated. The exact expression for the scattering cross section in terms of the generated Debye partial potentials that are dependent on the given refractive index has been obtained.     

Direct measurement of substrate refractive indices and determination of layer indices in slab-guiding structures

We present a new method for accurate and nondestructive measurement of the refractive indices of substrates and guiding layers in slab waveguides. This method is based on the excitation of leaky waves in substrates and guided waves in guiding layers owing to the etching of grating couplers on the top of structures. It is particularly applicable to high refractive-index materials and to in situ measurements near the energy band gap of semiconductor waveguides. We present results that were obtained for an InP substrate with an InGaAsP epitaxial layer with regard to their refractive indices and temperature coefficients.     

Low chromatic aberration of gradient refractive index rod lens for Na+/Li+ ion exchange using oxide compositions model

In this paper, the oxide compositions model (OC model) is established for discussing the chromatic aberrations of gradient refractive index rod lens. The chromatic aberration for Na⁺/Li⁺ ion exchanges is discussed based on the OC model and the Huggins–Sun–Davis (HSD) model. Theoretical result indicates that the function value mainly depends on base glass properties and nature of exchanging ion pairs, and hardly depends on the quantity of ion exchanging. Experimental results show that the chromatic aberrations using the OC model have smaller errors than them using the HSD model. The estimating average error between the OC model and the HSD model is ?0.0067 for the Na⁺/Li⁺ ion exchanges.     

Reconstruction of refractive indices from spectral measurements of monodisperse aerosols

For the investigation of two-component aerosols, one needs to know the refractive indices of the two aerosol components. One problem is that they depend on temperature and pressure, so one needs for their determination a robust measurement instrument such as the FASP device, which can cope with rigid environmental conditions. In this article, we show that the FASP device is capable of measuring the needed refractive indices, if monodisperse aerosols of the pure components are provided. We determine the particle radii of the monodisperse aerosols needed for this task and investigate how accurate the measurements have to be in order to retrieve refractive indices in a sufficient quality, such that they are suitable for investigations of two-component aerosols.     

Theory for the measurement of the linear and nonlinear refractive indices of double-clad fibers using an interferometric technique

Multiple-beam Fizeau fringes are formed across a liquid silvered wedge when it is illuminated by a collimated beam of monochromatic light. Inserting the fiber into the liquid silvered wedge causes the fringes to shift across the fiber region with respect to the fringes at the liquid region. Fringe shift is a function in the geometry of the different regions of the fiber and the refractive index profile of the fiber. In this paper, theoretical models for the fringe shift across double-clad fibers (DCFs) with rectangular, elliptical, circular, and D-shaped inner cladding are developed. An algorithm to reconstruct the linear and nonlinear terms of the refractive index profile of the DCF is outlined. Numerical examples are provided and discussed.     

Analysis of capillary interferometry for measuring refractive indices of minute samples

A method of measuring the refractive indices of minute samples by analyzing capillary interferometry is introduced. With the interference theory of light, the intensity distribution of an interference fringe pattern formed by a cylindrical tube of a capillary is obtained, and the influence of some parameters on the fringes are discussed. The measurement accuracy and its relative problems are analyzed.     

Optical filters with prescribed optical thickness and refined refractive indices

We propose to refine the refractive index of the layers composing optical filters while keeping their optical thicknesses constant. Using this technique, one can optimize filters made of quarter-wave layers using conventional optimization techniques, while preserving the possibility to use turning-point monitoring during their fabrication. Application of this method to the design of a dual narrowband filter and a tilted edge filter demonstrates its effectiveness.     

The refractive indices of some garnet crystals at 1.15 μm

Refractive index measurements for Y₃Fe₅O₁₂, (LaY)₃Ga_.33Fe_4.67O₁₂ and Ga₃Gd₅O₁₂ were obtained at 1.152 μm by observing optical waveguiding in epitaxial thin films.     

Measuring the refractive indices of liquids with a capillary tube interferometer

A theoretical analysis of the fringe pattern produced by a capillary tube interferometer is presented, which is expected to be two-beam interference, and a computer program to simulate the interference fringe pattern is established. By comparing the simulated fringe pattern and the experimental fringe pattern, the refractive index of the liquid can be given when the two fringes coincide best. The results of this method are close to those of the Abbe refractometer.     

Planar waveguide refractive index distribution functions determined precisely from mode indices

The inverse WKB (IWKB) approximation has been extended to derive the index distribution functions from the measured mode indices of a planar waveguide. Through the use of this technique, the forms of the index distribution functions are obtained by IWKB approximation and a criterion is used to derive the functions accurately. The results are compared to the exponential and Fermi distributions. It is shown that the index profile, surface index, and waveguide depth can be obtained more accurately than with the original IWKB approximation. Finally, the index distribution function of a c-cut proton-exchanged LiTaO(3) waveguide is given by this technique, the mode indices calculated with this function agree with the experimental results in the range of 10(-4).