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|Title: ||Numerical modelling of photonic crystal based switching devices|
|Authors: ||Selim, Ramsey|
|Issue Date: ||16-May-2012|
|Citation: ||Selim, R. (2010) Numerical modelling of photonic crystal based switching devices. Unpublished PhD thesis. University of Glamorgan.|
|Abstract: ||In the last few years research has identified Photonic Crystals (PhCs) as
promising material that exhibits strong capability of controlling light propagation in a
manner not previously possible with conventional optical devices. PhCs, otherwise
known as Photonic Bandgap (PBG) material, have one or more frequency bands in
which no electromagnetic wave is allowed to propagate inside the PhC. Creating
defects into such a periodic structure makes it possible to manipulate the flow of
selected light waves within the PhC devices outperforming conventional optical
devices. As the fabrication of PhC devices needs a high degree of precision, we have
to rely on accurate numerical modelling to characterise these devices.
There are several numerical modelling techniques proposed in literature for
the purpose of simulating optical devices. Such techniques include the Finite
Difference Time Domain (FDTD), the Finite Volume Time Domain (FVTD), and the
Multi-Resolution Time Domain (MRTD), and the Finite Element (FE) method
among many others. Such numerical techniques vary in their advantages,
disadvantages, and trade-offs. Generally, with lower complexity comes lower
accuracy, while higher accuracy demands more complexity and resources.
The Complex Envelope Alternating Direction Implicit Finite Difference Time
Domain (CE-ADI-FDTD) method was further developed and used throughout this
thesis as the main numerical modelling technique. The truncating layers used to
surround the computational domain were Uniaxial Perfectly Matched Layers
(UPML). This thesis also presents a new and robust kind of the UPML by presenting
an accurate physical model of discretisation error.
This thesis has focused on enhancing and developing the performance of PhC
devices in order to improve their output. An improved and new design of PhC based
Multiplexer/Demultiplexer (MUX/DEMUX) devices is presented. This is achieved
using careful geometrical design of microcavities with respect to the coupling length
of the propagating wave. The nature of the design means that a microcavity
embedded between two waveguides selects a particular wavelength to couple from
one waveguide into the adjacent waveguide showing high selectivity.
Also, the Terahertz (THz) frequency gap, which suffers from a lack of
switching devices, has been thoroughly investigated for the purpose of designing and
simulating potential PhC based switching devices that operate in the THz region.
The THz PhC based switching devices presented in this thesis are newly
designed to function according to the variation of the resonant frequency of a ring
resonator embedded between two parallel waveguides. The holes of the structures are
filled with polyaniline electrorheological fluids that cause the refractive index of the
holes to vary with applied external electric field. Significant improvements on the
power efficiency and wavelength directionality have been achieved by introducing
defects into the system.|
|Appears in Collections:||PhD theses|
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