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Effective optical constants n and κ and extinction coefficient of silica aerogel

Published online by Cambridge University Press:  31 January 2011

J. S. Q. Zeng ,
R. Greif ,
P. Stevens ,
M. Ayers  and
A. Hunt
J. S. Q. Zeng
Affiliation:
Department of Mechanical Engineering, University of California, Berkeley, California 94720
R. Greif
Affiliation:
Department of Mechanical Engineering, University of California, Berkeley, California 94720
P. Stevens
Affiliation:
Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720
M. Ayers
Affiliation:
Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720
A. Hunt
Affiliation:
Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720
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Abstract

In this work the normal reflectance, R, at a planar silica aerogel interface and the normal transmittance, T, of a silica aerogel slab were measured using a Fourier Transform Infrared Spectrometer. Two procedures were used to obtain the effective optical constants, i.e., the refractive index n and the absorption index κ, of silica aerogel. One procedure determined κ from the measured transmittance T and then determined n from the results for κ and from the measured reflectance R using the Kramers–Kronig relation; the other procedure determined n and κ of silica aerogel from n and κ of fully dense silica glass by using the Clausius–Mossotti equation, Maxwell Garnett formula, and Bruggeman formula. The first procedure has a relatively large error due to the inaccuracy of the transmission and reflection measurements. The second procedure, especially the Clausius–Mossotti equation, yields values of n that are consistent with experiments and may be used for the calculation of the effective optical constants and the extinction coefficient of silica aerogel.

Type
Articles
Information
Journal of Materials Research , Volume 11 , Issue 3 , March 1996 , pp. 687 - 693
Copyright
Copyright © Materials Research Society 1996

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References

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