| dc.description.abstract | This thesis provides an insight into the designing, physical realization and characterization
of optical transformation devices. It begins with an introduction to the discrete
coordinate transformation with a design example of a carpet cloak. The realization and
characterization of materials, namely a dielectric disk matrix and polyurethane/BaTiO3
foam composite, for constructing transformation optics devices are studied both numerically
and experimentally.
Two different kinds of low loss and broadband all-dielectric realisations of OT devices
are designed and experimentally demonstrated. First, the cloaking structure made of
a high-ǫ dielectric-loaded foam mixture is reported. A polyurethane foam, mixed with
different ratios of barium titanate is used to produce the required range of permittivities,
and the invisibility cloak is demonstrated to work for all incident angles, over a wide
range of microwave frequencies. Then, based on a study on the properties of periodic
dielectric particles, the cloak, realized with periodic dielectric cylinders, is proposed. The
required dielectric map for the cloak is achieved by means of manipulating the dimensions,
or spatial density, of the periodically distributed dielectric cylinders embedded in
the host medium, whose permittivity is close to one. The scattering reduction effects
are verified through both simulation and experimental results. The performances of the
two different kinds of cloak are also compared quantitatively. Last, but not least, an
extraordinary-transmission (ET) device made from commercially available ceramics and
Teflon is designed, which exhibits broadband transmission through a sub-wavelength
aperture. It is verified both numerically and experimentally that the device can provide
transmission with a -3 dB bandwidth of more than 1 GHz, in a region which would otherwise
be a stop band caused by the sub-wavelength aperture in an X-band waveguide. | en_US |
