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Application of modal techniques to multiply configured gratings


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Adams, JL 1981 , 'Application of modal techniques to multiply configured gratings', PhD thesis, University of Tasmania.

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The main theme of this thesis is the development of new rigorous
formalisms to describe the diffraction properties of multiply configured,
perfectly conducting, gratings with simple groove geometries. This class
of gratings is composed of singly or doubly periodic elements. The
formalisms are derived using modal techniques which are particularly
suited to solving the diffraction properties of these gratings.
Considerable attention is paid to the far infrared properties of the
gratings with the aim of describing their performance as interference
filters used in this wavelength range.
The thesis contains a general review of the previous contributions
to the theoretical study of diffraction gratings, including a review of
investigations which have been undertaken into the properties of far
infrared interferometers. This is followed by a discussion of a
formalism describing the diffraction properties of lossless dielectric
and finitely conducting gratings. This study represents one of the first
generalisations of a modal formalism to structures which are other
than perfectly conducting, and is a step towards the solution of the
diffraction properties of capacitive or finitely conducting inductive
The remainder of the thesis is concerned with perfectly conducting
gratings having basically rectangular geometries. The structures
considered are either singly periodic or doubly periodic. The double
periodicity results either directly from the geometry of the element (as
for example in the case of inductive grids) or is contrived by suitable
arrangement of singly periodic elements.
The performance of singly periodic interference filters, composed
of two or more lamellar gratings, is then described. The first such
structure to be considered is the double grating and the diffraction
properties of this arrangement are described in detail. The associated
analysis is performed by explicitly specifying the fields in each groove
region by a modal expansion. The geometry of the double grating is then
generalised to consider a grating composed of a stack of an arbitrary
number of singly periodic elements, and the properties of this structure
are analysed using a new rigorous multiple scattering technique.
These singly periodic gratings have application as Fabry-Perot
interferometers only for radiation having a particular linear polarization.
If the incident radiation is unpolarized it is necessary to use doubly
periodic devices such as inductive grids. For this reason the performance
of the double grid interferometer is considered, and a rigorous formalism
for it is derived using an approach similar to that used for the double
grating. The properties of multi-element grids are then analysed using a
multiple scattering approach.
Interesting conservation properties for lossless singly and doubly
periodic structures are presented and are related to the geometrical
symmetry of the structure. These relations provide constraints on the
scattering matrices of the diffraction system.
Finally, two formalisms are presented describing the diffraction
properties of a structure which is doubly periodic by virtue of the
positioning of its two singly periodic elements. This arrangement is
termed the crossed lamellar transmission grating. The first formalism
uses a modal expansion to describe the field within the grooves of each
element, while the second employs a rigorous multiple scattering approach.
In particular, it is demonstrated that this structure has application as a
solar heat mirror.

Item Type: Thesis - PhD
Authors/Creators:Adams, JL
Keywords: Diffraction gratings, Interferometry
Copyright Holders: The Author
Copyright Information:

Copyright 1981 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1981. Includes bibliographical references

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