Elektromanyetik dalgaların yayılmasının kontrolünde yeni yöntemler: Metamalzemeler ve fotonik kristaller

Applications in areas such as photonics, antennas, imaging and optics requirethe control of propagation of electromagnetic waves and the control of emission ofelectromagnetic radiation. Achievements in three key research fields may providethe answer to these problems. These emerging research fields are metamaterials,photonic crystals and surface plasmons. This thesis will be about our work onmetamaterials and photonic crystals. Metamaterials are a new class of artificialstructures whose electromagnetic response can be described by effective perme-ability and permittivity functions that may attain negative values. I will presentour results on the properties of a metamaterial structure that we proposed re-cently, the labyrinth structure. I will demonstrate that the labyrinth structurecan be used to design a medium that exhibits negative permeability values withina certain frequency range. Moreover, I will explore the possibility of negative re-fraction and sub-wavelength focusing of electromagnetic waves by two and three-dimensional labyrinth structure based left-handed mediums. Novel applicationssuch as metamaterial based compact size antennas, ultra-small high-Q cavitieswill be also discussed. Another type of artificial electromagnetic structures arethe photonic crystals. Photonic crystals can be described by a periodic modu-lation of the permittivity and/or the permeability of a medium. I will discusstwo phenomena arising from the dispersion properties of photonic crystals andtheir possible applications. One of these phenomena is the existence of surface-bound electromagnetic modes and the other is the negative refraction effect. Iwill further show that the surface-bound modes can be used for applications suchas beaming of electromagnetic waves and enhancement of transmission throughsub-wavelength apertures. In addition, I will demonstrate that the negative re-fraction effect can be utilized to focus electromagnetic waves emitted from a finitesize source.ivvKeywords: Metamaterial, photonic crystal, labyrinth structure, plasma frequency,negative refraction, sub-wavelength focusing, surface mode, beaming, enhancedtransmission .