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Proceedings Paper

Three-Layer Dielectric Stripline Filter For Guided-Wave Applications
Author(s): A B. Buckman
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Paper Abstract

A novel wavelength filtering mechanism in a three-layer dielectric stripline structure is described. The waveguide consists of two high-index layers separated by a low-index layer in which the fields are evanescent perpendicular to the layer surfaces. The stripline is defined by a local extremum in the thickness of the middle, low-index layer. The analysis shows that upper or lower wavelength limits for propagation along the stripline can be set by proper choice of the thicknesses of the two high-index layers, if all layer refractive indices are specified. Outside these limits, the modes arc contained in the direction perpendicular to the layer surfaces, but are leaky in the direction parallel to them. The wavelength filtering mechanism is explained in terms of the wavelength dependence of the mode profile within and without the stripline. In this three-layer structure, for a particular mode, there is a critical wavelength for which the dependence of propagation constant on the thickness of the middle layer vanishes. At this wavelength, the mode does not see the stripline at all. On one side of this critical wavelength the effective index is at a local maximum along the stripline axis, while on the other it is at a local minimum. In the former case the structure acts as a dielectric stripline waveguide, containing the mode near the axis, while in the latter case the mode leaks away parallel to the layer surfaces. The structure gives sharp cutoffs in the transmittance vs. wavelength, with none of the oscillations beyond cutoff characteristic of distributed Bragg reflection filters.

Paper Details

Date Published: 23 May 1984
PDF: 5 pages
Proc. SPIE 0464, Solid-State Optical Control Devices, (23 May 1984); doi: 10.1117/12.966221
Show Author Affiliations
A B. Buckman, The University of Texas (United States)

Published in SPIE Proceedings Vol. 0464:
Solid-State Optical Control Devices
Pochi Yeh, Editor(s)

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