THE DETERMINATION OF THE OPTICAL CONSTANTS OF SOME SILICATE GLASSES AT MILLIMETRE AND SUBMILLIMETRE WAVELENGTHS
Abstract
This work has two interlocking themes. It is primarily concerned with
the development of precise, broad band, Fourier transform spectrometric
techniques for the determination of the optical constants of solids at
millimetre and submillimetre wavelengths. One such technique cannot
easily accomodate the wide range of optical constants found in solids,
leading to specimens which range from the virtually transparent to the
virtually opaque, and it was therefore necessary to develop transmission
and reflection techniques. The intercomparison of these techniques, their
particular experimental difficulties and susceptibilities to random and
systematic error, was performed by using each method to determin'the
optical constants of soda lime silica glass over as wide a spectral
range as possible. Previous to this work there had been no systematic
study of this important material at these wavelengths and,thus, this
investigation gave the second theme of this work, the quantitative
determination of the optical constants of soda lime silica glass at
millimetre and submillimetre wavelengths.
The results of this study are presented in four chapters. First, in
chapter 5, power transmission Fourier transform spectrometry has been
used to investigate the spectral variation of the optical constants of
the glass between 3 and 50cm, using an analysis of channel spectra to
give the refractive index. This chapter also contains the results of
measurements made with a grating instrument between 1000 and k000cm.
Secondly, in chapter 6, the results of the first direct determinations
of the optical constants by dispersive transmission Fourier transform
spectrometry are presented and shown to indicate the presence of a
hitherto unknown loss process below 20er that is tentatively associated
with a similar process previously observed in fused silica. Thirdly, in
chapter 7, dispersive reflection Fourier transform spectrometry has been
used to determin the optical constants up to 360em, well into the midinfrared
region of opacity of this glass. The results of chapters 6 and
7 provide the first quantitative description of the optical constants of
this glass betweem 3 and 360em Finally, in chapter 8, the dispersive
reflection measurements are extended to simple binary and ternary
silicate glasses, and these results used to identify the contributions
to the mid-infrared absorption of the metal ions associated with the
various metal oxide additives of the glass. From this it was possible to
account for all of the absorption in soda lime silica glass as a
superposition of contributions from the near-infrared bands of the SiO1
network of the glass and the four main metal ions.
Authors
Birch, James RobertCollections
- Theses [3366]