Chiral metamaterial and high-contrast grating based polarization selective devices

View/ Open
Author
Mutlu, Mehmet
Advisor
Özbay, Ekmel
Date
2013Publisher
Bilkent University
Language
English
Type
Thesis
Metadata
Show full item recordPlease cite this item using this persistent URL
http://hdl.handle.net/11693/17065Abstract
The utilization of purposely designed artificial media with engineered electromagnetic
responses enables the obtaining of intriguing features that are either
impossible or difficult to realize using readily available natural materials. Here,
we focus on two classes of artificial media: metamaterials and high-contrast gratings.
Metamaterials and high-contrast gratings are designed within the subwavelength
periodicity range and therefore, they are non-diffractive. We exploit the
magnetoelectric coupling effect in chiral metamaterials to design several structures.
Firstly, we design a linear to circular polarization convertor that operates
for x-polarized normally incident plane waves. Then, we combine the chirality
feature and the electromagnetic tunneling phenomenon to design a polarization
insensitive 90◦ polarization rotator that exhibits unity transmission and crosspolarization
conversion efficiencies. Subsequently, we combine this polarization
rotator with a symmetric metallic grating with a subwavelength slit for the purpose
of enabling the one-way excitation of spoof surface plasmons and achieving
a reversible diodelike beaming regime. Then, we exploit the asymmetric transmission
property of chiral metamaterials and show that a polarization angle dependent
polarization rotation and a strongly asymmetric diodelike transmission
is realizable. Afterwards, a brief waveguide theory is provided and eventually,
the dispersion relations for a periodic dielectric waveguide geometry are derived.
Then, using these relations and considering the finiteness of the waveguide length,
we show the theoretical description of high-contrast gratings. Finally, we theoretically
and experimentally show that the achievement of a broadband quarter-wave
plate regime is possible by using carefully designed high-contrast gratings.