An apparatus for producing atomic-gas Bose-Einstein condensates (BECs) of 87-Rb atoms is described. The apparatus produces 87-Rb BECs in a dual-chamber vacuumsystem that incorporates magnetic transport of trapped atoms from the magneto-optical trapping cell to the BEC production cell via the operation of a series of overlapping magnet coils. The design, construction, and operation of the apparatus are described in detail.The apparatus is used to study the creation of quantized vortices in BECs by the merging and interference of multiple trapped condensates. In this experiment, a single harmonic potential well is partitioned into three sections by an optical barrier,enabling the simultaneous formation of three independent, uncorrelated BECs. The BECs may either merge together during their growth, or, for high-energy barriers, the BECs can be merged together by barrier removal after their formation. Either process may instigate vortex formation in the resulting BEC, depending on the initially indeterminate relative phases of the condensates and the merging rate.

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This thesis is devoted to potential applications of metamaterials in antenna structures as well as metamaterials behaviour, characterisation, structure design, simulation and extraction of parameters. The focus of this work is on the practical application of metamaterial structures for antenna performance enhancement. This thesis comprises three key parts; In the first part, theory of metamaterials is investigated including fields, polarisation, effective and average parameters, parameters extraction and transmission line (TL) model. In part two, zero index metamaterials (ZIM) theory is studied. The use of ZIM to form a highly directive medium is illustrated. A comparative study between different ZIM structures is conducted with a special attention to their operational bandwidth. ANSYS HFSS is used to model ZIM structures where simulation results show a bandwidth between 7.4% and 14.0%. Then two novel ZIM structures with a bandwidth of up to 33% are proposed. The first proposed ZIM is used to form a highly directive shell. Four directive shells are designed and placed around the dipole antenna where a gain increase of up to 6.8 dBi is obtained along the desired direction. Further, proposed ZIM cells are integrated with a quasi-Yagi antenna in order to increase its gain. Simulation results demonstrate gain enhancement for frequencies over which the proposed structure expresses ZIM properties. In part three, a new technique is stablished to design a metamaterial lens. The new technique is based on wave interference phenomena where engineered wave interference results in a desired spatial energy distribution. It is shown theoretically that having 180° phase difference between interfering waves results in a focused emission. Both hypothetical and metamaterial realisation models of a 180° phase shifter for a patch antenna are designed and simulated where a gain enhancement of 8 dBi and 5.77 dBi are achieved, respectively. Further, the concept of intended phase shift between interfering waves is used to design a novel bi-reflectional ground plane which can focus the reflected emission and consequently, increase the antenna directivity. In the theoretical model, the Perfect-E and Perfect-H planes are combined to form a bi-reflectional plane, whereas the practical model is designed using the copper cladding for the Perfect-E plane and the mushroom structure for the perfect-H plane. Both square and hexagonal geometries are used to form the mushroom structure. Simulation results confirm a gain enhancement of 5.4 dBi for the design using the square mushroom structure and a gain enhancement of 3.3 dBi for the design using the hexagonal mushroom structure.

The spectral and directional control of radiative properties by utilizing engineered micro/nanostructures has enormous applications in photonics, microelectronics, and energy conversion systems. The present dissertation aims at: (1) design and analysis of micro/nanostructures based on wave interference and magnetic resonance effects to achieve tunable coherent thermal emission or enhanced optical transmission; (2) microfabrication of the designed structures; and (3) development of a high-temperature emissometer to experimental demonstrate coherent thermal emission from fabricated samples at temperatures from 300 K to 800 K. Asymmetric Fabry-Perot resonant cavities were studied as a potential coherent emission source. The reflectance was measured at room temperature using a Fourier-transform infrared spectrometer, and the emittance can be indirectly obtained from Kirchhoff's law. A high-temperature emissometer was built to measure the thermal emission of fabricated samples, and the temperature effect on the emission peaks was discussed. The direct and indirect approaches were unified and a generalized Kirchhoff's law was deduced to calculate thermal emission from layered structures with nonuniform temperatures. Magnetic polaritons were identified as a mechanism for achieving extraordinary optical transmission/absorption, through the comparison between equivalent capacitor-inductor models and the rigorous coupled-wave analysis. With carefully tuned geometric parameters, the resonance frequencies can be tailored for specific applications. A coherent emission source was designed with grating structures by excitation of magnetic polaritons, and is well suitable for thermophotovoltaic applications, thanks to the spectral selectivity and directional insensitivity of magnetic polaritons. Test samples were fabricated, and coherent thermal emission was experimentally observed at room temperatures up to 800 K. The results obtained in this dissertation will facilitate the design and application of micro/nanostructures in energy-harvesting systems.

Ultra-cold dilute gases of neutral atoms are attractive candidates for creating controlled mesoscopic quantum systems. In particular, quantum degenerate gases of bosonic and fermionic atoms can be used to model the correlated many-body behaviour of Bose and Fermi condensed matter systems, and to study matter wave interference and coherence. This thesis describes the experimental realization and manipulation of Bose-Einstein condensates (BECs) of 87Rb and degenerate Fermi gases (DFGs) of 40K using static and dynamic magnetic atom chip traps. Atom chips are versatile modern tools used to manipulate atomic gases. The chips consist of micrometre-scale conductors supported by a planar insulating substrate, and can be used to create confining potentials for neutral atoms tens or hundreds of micrometres from the chip surface. We demonstrate for the first time that a DFG can be produced via sympathetic cooling with a BEC using a simple single-vacuum-chamber apparatus. The large 40K-87Rb collision rate afforded by the strongly confining atom chip potential permits rapid cooling of 40K to quantum degeneracy via sympathetic cooling with 87Rb. By studying 40K-87Rb cross-thermalization as a function of temperature, we observe the Ramsauer-Townsend reduction in the 40K-87Rb elastic scattering cross-section. We achieve DFG temperatures as low as T = 0.1TF , and observe Fermi pressure in the time-of-flight expansion of the gas. This thesis also describes the radio-frequency (RF) manipulation of trapped atoms to create dressed state double-well potentials for BEC and DFG.We demonstrate for the first time that RF-dressed potentials are species-selective, permitting the formation of simultaneous 87Rb double-well and 40K single-well potentials using a 40K-87Rb mixture. We also develop tools to measure fluctuations of the relative atom number and relative phase of a dynamically split 87Rb BEC. In particular, we observe atom number fluctuations at the shot-noise level using time-of-flight absorption imaging. These measurement tools lay the foundation for future investigations of number squeezing and matter wave coherence in BEC and DFG systems.

Ultra-cold dilute gases of neutral atoms are attractive candidates for creating controlled mesoscopic quantum systems. In particular, quantum degenerate gases of bosonic and fermionic atoms can be used to model the correlated many-body behaviour of Bose and Fermi condensed matter systems, and to study matter wave interference and coherence. This thesis describes the experimental realization and manipulation of Bose-Einstein condensates (BECs) of 87Rb and degenerate Fermi gases (DFGs) of 40K using static and dynamic magnetic atom chip traps. Atom chips are versatile modern tools used to manipulate atomic gases. The chips consist of micrometre-scale conductors supported by a planar insulating substrate, and can be used to create confining potentials for neutral atoms tens or hundreds of micrometres from the chip surface. We demonstrate for the first time that a DFG can be produced via sympathetic cooling with a BEC using a simple single-vacuum-chamber apparatus. The large 40K-87Rb collision rate afforded by the strongly confining atom chip potential permits rapid cooling of 40K to quantum degeneracy via sympathetic cooling with 87Rb. By studying 40K-87Rb cross-thermalization as a function of temperature, we observe the Ramsauer-Townsend reduction in the 40K-87Rb elastic scattering cross-section. We achieve DFG temperatures as low as T = 0.1TF , and observe Fermi pressure in the time-of-flight expansion of the gas. This thesis also describes the radio-frequency (RF) manipulation of trapped atoms to create dressed state double-well potentials for BEC and DFG.We demonstrate for the first time that RF-dressed potentials are species-selective, permitting the formation of simultaneous 87Rb double-well and 40K single-well potentials using a 40K-87Rb mixture. We also develop tools to measure fluctuations of the relative atom number and relative phase of a dynamically split 87Rb BEC. In particular, we observe atom number fluctuations at the shot-noise level using time-of-flight absorption imaging. These measurement tools lay the foundation for future investigations of number squeezing and matter wave coherence in BEC and DFG systems.