Infrared Reflectance Characterization of a GaAs-AlAs Superlattice

1986 ◽  
Vol 90 ◽  
Author(s):  
J. M. Zavada ◽  
G. K. Hubler ◽  
H. A. Jenkinson ◽  
W. D. Laidig
Keyword(s):  
Refractive Index ◽  
Dielectric Function ◽  
Absorption Edge ◽  
Reflectance Spectrum ◽  
Least Squares Method ◽  
Alloy Film ◽  
Infrared Reflectance ◽  
A Value ◽  
Non Destructive

ABSTRACTThe optical properties of a GaAs-AlAs superlattice have been examined using the non-destructive technique of infrared reflectance spectroscopy. Through this technique, the absorption edge, the effective superlattice refractive index, the thickness, and the optical grading of the superlattice-substrate were determined. Location of the absorption edge was made from the reflectance spectrum and showed general agreement with photoluminescence measurements. A more detailed analysis of the infrared spectra indicated the presence of a transition region between the substrate and the superlattice. Based on a non-linear least squares method for fitting the experimental data, a dispersion relation for the dielectric function was obtained. This dielectric function yielded a value for the superlattice refractive index that was lower than that of the corresponding, homogeneous, AlGaAs alloy film for wavelengths between 1.0 and 2.5 micrometers.

scholarly journals Identification of pigments in artworks by inverse tangent derivative of spectrum and a new filtering method

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
F. Fazlali ◽  
S. Gorji Kandi
Keyword(s):  
Reflectance Spectrum ◽  
Practical Method ◽  
Chemical Methods ◽  
Munk Function ◽  
Absorption Of Light ◽  
Spectrophotometric Data ◽  
First Time ◽  
Non Destructive ◽  
Derivatives Of

Abstract Employing an economical and non-destructive method for identifying pigments utilized in artworks is a significant aspect for preserving their antiquity value. One of the non-destructive methods for this purpose is spectrophotometry, which is based on the selected absorption of light. Mathematical descriptive methods such as derivatives of the reflectance spectrum, the Kubelka–Munk function and logarithm have been employed for the characterization of the peak features corresponding to the spectrophotometric data. In the present study, the mentioned mathematical descriptive methods were investigated with the aim to characterize the constituents of an Iranian artwork but were not efficient for the samples. Therefore, inverse tangent derivative equation was developed on spectral data for the first time, providing considerable details in the profile of reflectance curves. In the next part, to have a simpler and more practical method it was suggested to use filters made up of pure pigments. By using these filters and placing them on the samples, imaging was done. Then, images of samples with and without filter were evaluated and pure pigments were distinguished. The mentioned methods were also used to identify pigments in a modern Iranian painting specimen. The results confirmed these methods with reliable answers indicating that physical methods (alongside chemical methods) can also be effective in determining the types of pigments.

scholarly journals Automatic Characterization of the Refractive Index Profile of Fibers by Interferometry

2002 ◽  
Vol os-11 (1) ◽  
pp. 1558925002OS-01
Author(s):  
Han Seong Kim ◽  
Behnam Pourdeyhimi
Keyword(s):  
Refractive Index ◽  
Interference Fringe ◽  
Axial Direction ◽  
Refractive Index Profile ◽  
Path Difference ◽  
Fringe Field ◽  
Index Profile ◽  
Degree Of Orientation ◽  
Non Destructive

Interferometry provides a non-destructive method for examining the refractive index profile or the radial birefringence distribution within fibers. The key step in the interference data reduction involves the extraction of the refractive index profile along the axial direction of the fiber. The profile is due to the path difference between the fiber and the immersion liquid when a fiber is oriented perpendicular to the fringe field in an interference microscope. The refractive index provides a measure of the degree of optical anisotropy and is indicative of the degree of orientation of the structure. This is of particular interest to nonwovens because in thermally bonded nonwovens, the orientation plays a major role in how well the fibers are bonded and the ultimate properties of the fabric. Despite its long history, however, the interpretation of the interference fringe shift is not precisely defined. Consequently, the data are not reproducible from one laboratory to the next. We outline below an objective and quantitative method for precisely measuring a fiber's refractive index profile from a digitized image of the interference fringe. This new algorithm uses the Fast Fourier Transform (FFT) to remove the inherent noise present in the fiber interferogram and to aid in extracting the profile.

Optical Technique for Characterization of High Energy Ion Implanted Materials

1992 ◽  
Vol 268 ◽  
Author(s):  
Gustavo E Aizenberg ◽  
Pieter L Swart ◽  
Beatrys M Lacquet
Keyword(s):  
Refractive Index ◽  
Digital Signal ◽  
Amorphous Layer ◽  
High Energy ◽  
Optical Technique ◽  
Concentration Peak ◽  
Non Destructive ◽  
Reflectance Data ◽  
Ion Implanted

ABSTRACTA new method for the characterization of high energy ion-implanted materials has been developed. The refractive index and thickness of the amorphous layer produced by ion-implantation as well as the recrystallized layer formed by annealing of the ionimplanted samples can be determined by means of this non-destructive optical technique.For frequencies where the carriers do not respond, the measured reflectance is bilinear transformed, and further digital signal processing yields information about thickness and refractive index of the abovementioned layers. When working at optical frequencies where the carriers can respond to the electromagnetic field the physical position of the peak concentration follows directly from the processed reflectance data. Simulated and experimental data have been analyzed. The position of the boundaries between the amorphous, recrystallized and substrate zones, as well as the position of the carrier concentration peak can be determined for various steps of annealing. The algorithm has the advantage of being simple and time efficient.

Reverse engineering of AlxGa1−xAs/GaAs structures composition by reflectance spectroscopy

2011 ◽  
Vol 19 (4) ◽  
Author(s):  
M. Wośko ◽  
B. Paszkiewicz ◽  
K. Tarnowski ◽  
B. Ściana ◽  
D. Radziewicz ◽  
...  
Keyword(s):  
Reverse Engineering ◽  
Reflectance Spectrum ◽  
Reflectance Spectroscopy ◽  
Experimental Results ◽  
Spectral Measurements ◽  
Spectrum Matching ◽  
Non Destructive ◽  
Sensitive Method

AbstractThe paper presents the application of non-modulation reflectance method for composition profiling of epitaxial AlxGa−xAs/GaAs structures. This non-destructive method is based on spectral measurements and theoretical reflectance spectrum matching. This is a very accurate and sensitive method of determining the Al composition in AlxGa1−xAs layers and structures with resolution down to 1 nm. In this work, the authors describe theoretic principles of this method and present experimental results of characterization of different AlGaAs structures to prove the potential of the worked out method.

Determination of the Complex Refractive Index of Materials via Infrared Measurements

2002 ◽  
Vol 56 (8) ◽  
pp. 1107-1113 ◽  
Author(s):  
Christos-Platon E. Varsamis
Keyword(s):  
Refractive Index ◽  
Dielectric Function ◽  
Complex Refractive Index ◽  
Infrared Reflectance ◽  
Finite Samples ◽  
Interference Fringes ◽  
Infrared Measurements ◽  
Optical Effects ◽  
Si Wafer

In this work, methods are presented for obtaining the real, n, and imaginary, k, parts of the complex refractive index of materials considered as semi-infinite and finite from infrared reflectance, R( ν), and/or transmittance, T( ν), spectra. In semi-infinite samples, with negligible T( ν), only R( ν) is measured, and n and k can derive from the Kramers–Kronig (K–K) transformation or the modeling of the dielectric function of the material. In finite samples, the interference fringes due to multiple internal reflections can significantly alter the measured spectra. It was demonstrated that whenever the period of the fringes is on the order of a few cm−1, n and k can be equivalently obtained by the extended K–K analysis for T( ν) spectra, the modeling of the dielectric function, and the inversion of low-resolution R( ν) and T( ν) spectra, as well as the acquisition of a single high-resolution R( ν) or T( ν) spectrum. Otherwise, n and k can be calculated by modeling the dielectric function of the material once the optical effects are carefully removed. These methods were applied in infrared measurements of crystalline Si wafer and of glassy 0.20AgI·0.80[Ag2O·2B2O3].

MEASUREMENT OF THE INTENSITY-DEPENDENT REFRACTIVE INDEX USING COMPLETE SPATIO-TEMPORAL PULSE CHARACTERIZATION

2005 ◽  
Vol 14 (01) ◽  
pp. 9-20 ◽  
Author(s):  
GIOVANNI PIREDDA ◽  
CHRISTOPHE DORRER ◽  
ELLEN M. KOSIK WILLIAMS ◽  
IAN A. WALMSLEY ◽  
ROBERT W. BOYD
Keyword(s):  
Refractive Index ◽  
Phase Modulation ◽  
Optical Glass ◽  
Optical Parameters ◽  
Transverse Coordinate ◽  
A Value ◽  
Spatio Temporal ◽  
Pulse Characterization ◽  
Good Agreement

We use complete spatio-temporal characterization of an ultrashort pulse to study self-phase modulation and other propagation effects in a sample of SF59 optical glass. The goal of this work is to perform accurate experimental measurements of the optical parameters of material samples. From the measured dependence of the self-induced phase shift on the transverse coordinate, we deduce a value of the coefficient n2 of the intensity-dependent refractive index that is in good agreement with previous measurements. We also observe that the spectrum of the transmitted pulse can be explained only approximately in terms of the solution to the nonlinear Schrödinger equation.

scholarly journals Identification of pigments in artworks by inverse tangent derivative of spectrum and a new filtering method

2020 ◽  
Author(s):  
Fatemeh Fazlali ◽  
Saeideh GORJI KANDI
Keyword(s):  
Reflectance Spectrum ◽  
Practical Method ◽  
Chemical Methods ◽  
Munk Function ◽  
Absorption Of Light ◽  
Spectrophotometric Data ◽  
First Time ◽  
Non Destructive ◽  
Derivatives Of

Abstract Employing an economical and non-destructive method for identifying pigments utilized in artworks is a significant aspect for preserving their antiquity value. One of the non-destructive methods for this purpose is spectrophotometry, which is based on the selected absorption of light. Mathematical descriptive methods such as derivatives of the reflectance spectrum, the Kubelka-­Munk function and logarithm have been employed for the characterization of the peak features corresponding to the spectrophotometric data. In the present study, the mentioned mathematical descriptive methods were investigated with the aim to characterize the constituents of an Iranian artwork but were not efficient for the samples. Therefore, inverse tangent derivative equation was developed on spectral data for the first time, providing considerable details in the profile of reflectance curves. In the next part, to have a simpler and more practical method it was suggested to use filters made up of pure pigments. By using these filters and placing them on the samples, imaging was done. Then, images of samples with and without filter were evaluated and pure pigments were distinguished. The mentioned methods were also used to identify pigments in a modern Iranian painting specimen. The results confirmed these methods with reliable answers indicating that physical methods (alongside chemical methods) can also be effective in determining the types of pigments.

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