Fresnel reflection coefficient

A grazing angle objective on an infrared microspectrometer is studied for quantitative spectroscopy by considering the angular dependence of the incident intensity within the objective's angular aperture. The assumption that there is no angular dependence is tested by comparing the experimental reflectance of Si and KBr surfaces with the reflectance calculated by integrating the Fresnel reflection coefficient over the angular aperture under this assumption. Good agreement was found, indicating that the specular reflectance of surfaces can straightforwardly be quantitatively integrated over the angular aperture without considering nonuniform incident intensity. This quantitative approach is applied to the thickness determination of dipcoated Krytox on gold. The infrared optical constants of both materials are known, allowing the integration to be carried out. The thickness obtained is in fair agreement with the value determined by ellipsometry in the visible. Therefore, this paper illustrates a method for more quantitative use of a grazing angle objective for infrared reflectance microspectroscopy.

Download Full-text

Accounting for Antenna in Half-Space Fresnel Coefficient Estimation

International Journal of Geophysics ◽

10.1155/2012/138458 ◽

2012 ◽

Vol 2012 ◽

pp. 1-11 ◽

Cited By ~ 1

Author(s):

A. D'Alterio ◽

R. Solimene

Keyword(s):

Reflection Coefficient ◽

Half Space ◽

Estimation Procedure ◽

Reflection Coefficients ◽

Fresnel Reflection ◽

Reflection Mode ◽

Coefficient Estimation ◽

Fresnel Coefficient ◽

Different Types

The problem of retrieving the Fresnel reflection coefficients of a half-space medium starting from measurements collected under a reflection mode multistatic configuration is dealt with. According to our previous results, reflection coefficient estimation is cast as the inversion of linear operator. However, here, we take a step ahead towards more realistic scenarios as the role of antennas (both transmitting and receiving) is embodied in the estimation procedure. Numerical results are presented to show the effectiveness of the method for different types of half-space media.

Download Full-text

Evaluation and Analysis of Attenuated Total Reflectance FT-IR Spectra Using Kramers-Kronig Transforms

Applied Spectroscopy ◽

10.1366/0003702924926970 ◽

1992 ◽

Vol 46 (11) ◽

pp. 1666-1672 ◽

Cited By ~ 39

Author(s):

J. B. Huang ◽

M. W. Urban

Keyword(s):

Iterative Process ◽

Absorption Index ◽

Attenuated Total Reflectance ◽

Initial Estimate ◽

Fresnel Reflection ◽

Total Reflectance ◽

Fresnel Reflection Coefficient ◽

Reflectivity Spectra ◽

Ft Ir ◽

The Difference

Two commonly used correction algorithms that were originally developed by Bertie and Dignam and their co-workers for quantitative analysis of ATR spectra are examined. It is shown that the Dignam theory is more suitable for strong ATR bands, whereas the Bertie algorithm is more applicable for weak bands. On the basis of analysis of possible deviation sources determined in the Bertie and Dignam theories, a new ATR algorithm is developed and analyzed. With this approach, the initial estimate of the absorption index spectrum is obtained by KK correlation of the intensity and the phase of the complex Fresnel reflection coefficient. An iterative process that minimizes the difference between the true and calculated reflectivity spectra while maintaining the KK relation between refractive and absorption indices is used in conjunction with the Maclaurin numerical KKT method. Such an approach appears to improve accuracies for both weak and strong ATR bands.

Download Full-text