Refractive Index Of Substrate Research Articles

Bragg coupling efficiency for guided acoustooptic interaction in GaAs

The guided acoustooptical interaction on the (100) plane of GaAs is investigated as a function of waveguide thickness type of mode, acoustic frequency, direction of acoustic wave propagation, and substrate refractive index Our calculated results indicate that best efficiency is obtained for TE(0) ? TE(0) optical modes and for acoustic surface wave propagating along the ?01l? direction at a waveguide thickness close to cut-off Under these conditions, approximately 75 mW of acoustic power is required for 100% diffraction. For a transducer aperture giving 50 Omega of radiation resistance, the rf bandwidth of the diffraction is limited essentially by the frequency bandwidth of the interdigital transducer. A comparison of the calculated results with experimental data at 1.06-microm optical wavelength is also given.

Ellipsometer data analysis of a multilayer film with a suitable computer program

Several methods have already been devised for determining n, k and d for an absorbing single film by varying the experimental conditions to increase the number of ellipsometer readings: 1. (i)with single films of unknown optical constants and of various thickness; 2. (ii)with single films at various angles of incidence; 3. (iii)with single films in various surrounding media of known refractive index n 0; 4. (iv)with single films on various substrates of known refractive index. In the case of a multilayer absorbing or non-absorbing film an extension of these methods can be used to determine the optical constants and thickness of the individual layers of the film. This paper describes a computer method based on a non-linear least squares curve fitting for determining the optical constants and thickness of the individual layers by applying experimental conditions (i) or (ii) or both.

Radiation pattern of an end-fire optical waveguide coupler

A section of an optical waveguide having thickness less than the mode cutoff value adjoining a section having thickness greater than this value serves as an input-output optical waveguide coupler. Expressions for the radiation pattern of this coupler, the angle at which the maximum occurs, and the angular beam width are derived. Calculations of these quantities as a function of coupler thickness for several waveguide-substrate structures applicable at λ = 10.6 μm are presented. Radiation patterns with small angular widths that result in high coupler efficiencies are found to occur when the waveguide and substrate refractive indices are nearly equal.

ChemInform Abstract: MEASUREMENT OF FILM THICKNESS FROM LATTICE ABSORPTION BANDS

AbstractEin Verfahren zur Bestimmung der Dicke halbleitender oder isolierender Filme aus den IR‐Gitterabsorptionsbanden wird beschrieben.

Measurement of Film Thickness from Lattice Absorption Bands

Many compound semiconductors and insulators exhibit characteristic infrared lattice absorption bands which can be quantitatively described by classical dispersion theory. When the dispersion parameters are known, the thickness of an absorbing film on a nonabsorbing substrate can be determined from a measurement of the lattice absorption. For thin films the dispersion parameters can differ from the values appropriate to bulk single crystals; however, it is shown that the parameter most susceptible to variation can be obtained directly from the measured absorption band without knowledge of the film thickness. It is also shown that the integrated optical density (the area under the band plotted as optical density vs. wave number) is a linear function of thickness when the refractive index of the substrate is unity, but departs from linearity as the substrate refractive index increases. The appropriate equations and a method for determining film thickness from a measured absorption band are given. The discussion is illustrated by data for thin films on Si substrates.

Proton-implanted GaP optical waveguide

Waveguiding in the visible spectrum has been observed in proton-implanted n-type GaP. The results obtained indicate that waveguide formation results from free carrier index change of the substrate refractive index with respect to that of the implanted layer.

Comparative study of Vašíček's theory, Murmann-Försterling's theory and single reflection theory of thin film optics

Vašíček's theory and the Murmann-Försterling theory for determining the optical constants of thin metallic films, using ellipsometric parameters, are compared with the single reflection theory. Optical constants for thin metallic films are theoretically evaluated for wide ranges of azimuth ψ, phase difference Δ and film thickness/wavelength factor; the three theories are studied by comparing optical constants obtained for various values of the film thickness/wavelength factor. It is shown that the three theories lead to almost the same values of optical constants for certain ranges of variables. It is further shown that in other ranges, Vašíček's theory and the Murmann-Försterling theory agree with each other or one of them agrees with the single reflection theory. However, the study is restricted to the following values only: angle of incidence 75°, and refractive indices of substrate and air 1.500 and 1.000, respectively.

Note on the constant - reflectivity method of determining substrate optical constants

The “constant-reflectivity” method for determining all the optical parameters of a system of an isotropic nonabsorbing film on an isotropic absorbing substrate using ellipsometry is examined. It is shown that this technique can only be considered for either very high or very low ratios of substrate extinction coefficient to substrate refractive index and even then caution must be exercised. This infers that the calculational method is very sensitive to the material involved.

Matching a multilayer stack to a high refractive index substrate by means of an inhomogeneous layer

Matching a multilayer stack to a high refractive index substrate by means of an inhomogeneous layer