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An innovative approach for characterization of one dimensional Photonic Band Gap structures comprised of metallic inclusions (i.e. subwavelength dipole elements or resonant ring elements) is presented. Through an efficient S- to T-parameters conversion technique, a detailed analysis has been performed to investigate the variation of the dispersion characteristics of 1-D PBG structures as a function of the cell element configuration. Also, for the first time, the angular sensitivity of the structure has been studied in order to obtain the projected band diagrams for both TE and TM polarizations. Polarization sensitivity of the subwavelength cell element is exploited to propose a novel combination of elements which allows achieving PBGs with simultaneous frequency and polarization selectivity. The proposed approach demonstrates that the dispersion characteristic of each orthogonal polarization can be independently adjusted with dipole elements parallel to that same polarization. Generally, the structure has potential applications in orthomode transducer, and generally whenever the polarization of the incoming signal is to be used as a means of separating it from another signal in the same frequency band that is of orthogonal polarization. The current distribution and the resonance behavior of the ring element is studied and the effect of resonance on dispersion characteristics of 1-D PBGs composed of rings is investigated for the first time, for both individual and coupled rings. Interestingly, it is observed that 1-D PBG composed of resonant elements consistently has a bandgap around the resonant frequency of the single layer structure.

"Photonic crystals have recently been the subject of studies for use in optical signal processing. In particular, a Coupled Resonator Optical Waveguide (CROW) structure has been considered by M. F. Yanik and S. Fan in “Stopping Light All Optically” for use in a time-varying optical system for the storage of light in order to mitigate the effects of waveguide dispersion. In this thesis, the effects of the thermal field on the state stored in such a structure is studied. Through simulation, this thesis finds that when this structure is constructed of gallium arsenide cylinders in air, loss of the signal was found to be caused by free-carrier absorption, and the decay of the signal dominates over thermal spreading of the optical signal’s spectrum."

An innovative approach for characterization of one dimensional Photonic Band Gap structures comprised of metallic inclusions (i.e. subwavelength dipole elements or resonant ring elements) is presented. Through an efficient S- to T-parameters conversion technique, a detailed analysis has been performed to investigate the variation of the dispersion characteristics of 1-D PBG structures as a function of the cell element configuration. Also, for the first time, the angular sensitivity of the structure has been studied in order to obtain the projected band diagrams for both TE and TM polarizations. Polarization sensitivity of the subwavelength cell element is exploited to propose a novel combination of elements which allows achieving PBGs with simultaneous frequency and polarization selectivity. The proposed approach demonstrates that the dispersion characteristic of each orthogonal polarization can be independently adjusted with dipole elements parallel to that same polarization. Generally, the structure has potential applications in orthomode transducer, and generally whenever the polarization of the incoming signal is to be used as a means of separating it from another signal in the same frequency band that is of orthogonal polarization. The current distribution and the resonance behavior of the ring element is studied and the effect of resonance on dispersion characteristics of 1-D PBGs composed of rings is investigated for the first time, for both individual and coupled rings. Interestingly, it is observed that 1-D PBG composed of resonant elements consistently has a bandgap around the resonant frequency of the single layer structure.

Photonic crystals, periodic dielectric structures that control photons in a similar way that atomic crystals control electrons, present opportunities for the unprecedented control of light. Photonic crystals display a wide gamut of properties, such as the photonic band gap, negative index of refraction, slow or stationary modes, and anomalous refraction and propagation effects. This thesis investigates the modeling, simulation, fabrication, and measurement of two-dimensional square lattice photonic crystals. An effective index model was developed to describe the propagation of electromagnetic waves in the media and applied to characterize the behavior of self-collimated beams to discern the effect of the photonic crystal on the evolution of the amplitude and phase of the propagating beam. Potential applications include optical interconnects and stand alone devices such as filters and lasers. Based on design parameters from the simulations, two dimensional photonic crystals were fabricated on amorphous and single crystal silicon-on-insulator substrates utilizing electron beam lithography and inductively coupled plasma etching. A unique etching process utilizing a combination of Cl2 and C4F6 gases was developed and characterized which displayed a vertical profile with a sidewall angle of under 1 degree from vertical and very smooth sidewalls for features as small as 150 nm. The high quality of the etching was the key to obtaining extremely low loss, low noise structures, making feasible the fabrication of large area photonic crystal devices that are necessary to measure propagation phenomena. Reflectivity measurements were used to directly observe the photonic band structure with excellent correlation with theory. A device was designed and fabricated which successfully verified the prediction of the simulations through measurements of the self-collimation effect across a broad range of infrared wavelengths. A solid foundation for the necessary components (simulation, modeling, design, fabrication, and measurement) of two-dimensional photonic crystal has been demonstrated. Elements from solid state physics, materials science, optics, and electromagnetics were incorporated to further the understanding of the mechanism of beam propagation in photonic crystals and illuminating the vast potential of research in periodic media.

The absence of appropriate media to cultivate photons efficiently at the micro or nano scale has hindered taking the full advantage of processing information with light. The proposal of such a medium for light, known as photonic crystals (PCs)--multi-dimensional artificially periodic dielectric media--brings the possibility of a revolution in communications and sensing much closer. In such media, one can manipulate light at a scale on the order of the wavelength or even shorter. Applications of PCs other than in communication include bio-sensing because of the peculiar properties of PCs such as the capability of enhance field-matter interaction and control over the group velocity. As a result, PC waveguide (PCW) structures are of interest and it is expected that PC sensors offer the feasibility of multi-analyte and compact sensing schemes as well as the ability of the detection of small absolute analyte quantities (nanoliters) and low-concentration samples (picomoles), which may be advantages over conventional approaches such as fiber optic and slab waveguide sensors. Depending on the nature of the analyte, either dispersive or absorptive sensing schemes may be implemented. Light propagation is controlled fully only with 3D PCs. One of the problems arising due to reducing the dimension to 2D is that PCs become strongly polarization sensitive. In many cases, one wants to implement polarization insensitive devices such that the PC provides a full band gap for all polarizations. To address this problem, a novel type of PC called annular PC is proposed and analyzed. The capability of tuning the TE and TM polarizations independently within the same structure provides great flexibility to produce polarization-independent or polarization-dependent devices as desired. PCW bends are expected to be the essential building blocks of photonic integrated circuits. Sharp corners having small radii of curvature can be obtained. To enhance the low-loss and narrow-band transmission through these bends, PC heterostructures waveguide concept is introduced. We show that in PCWs formed by joining different types of PCs in a single structure, light can flow around extremely sharp bends in ways that are not possible using conventional PCWs based on a single type of PC.

Because of their outstanding characteristics, micro/nano-mechanical (MM) structures have found a plethora of applications in wireless communications and sensing. Many of these MM structures utilize mechanical vibrations (or phonons) at megahertz or gigahertz frequencies for their operation. On the other hand, the periodic atomic structure of crystals is the fundamental phenomenon behind the new era of electronics technology. Such atomic arrangements lead to a periodic electric potential that modifies the propagation of electrons in the crystals. In some crystals, e.g. silicon (Si), this modification leads to an electronic band gap (EBG), which is a range of energies electrons can not propagate with. Discovering EBGs has made a revolution in the electronics and through that, other fields of technology and the society. Inspired by these trends of science and technology, I have designed and developed integrated MM periodic structures that support large phononic band gaps (PnBGs), which are ranges of frequencies that phonons (and elastic waves) are not allowed to propagate. Although PnBGs may be found in natural crystals due to their periodic atomic structures, such PnBGs occur at extra high frequencies (i.e., terahertz range) and cannot be easily engineered with the current state of technology. Contrarily, the structures I have developed in this research are made on planar substrates using lithography and plasma etching, and can be deliberately engineered for the required applications. Although the results and concepts developed in this research can be applied to other substrates, I have chosen silicon (Si) as the substrate of choice for implementing the PnBG structure due to its unique properties. I have also designed and implemented the fundamental building blocks of MM systems (e.g., resonators and waveguides) based on the developed PnBG structures and have shown that low loss and efficient MM devices can be made using the PnBG structures. As an example of the possible applications of these PnBG structures, I have shown that an important source of loss, the support loss, can be suppressed in MM resonators using PnBG structures. I have also made improvements in the characteristics of the developed MM PnBG resonators by developing and employing PnBG waveguides. I have further shown theoretically, that photonic band gaps (PtBGs) can also be simultaneously obtained in the developed PnBGs structures. This can lead to improved photon-phonon interactions due to the effective confinement of optical and mechanical vibrations in such structures. For the design, fabrication, and characterization of the structures, I have developed and utilized complex and efficient simulation tools, including a finite difference time domain (FDTD), a plane wave expansion (PWE), and a finite elements (FE) tool, each of which I have developed either completely from scratch, or by modification of an existing tool to suit my applications. I have also developed and used advanced micro-fabrication recipes, and characterization methods for realizing and characterizing these PnBG structures and devices. It is agued that by using the same ideas these structures can be fabricated at nanometer scales to operate at ultra high frequency ranges. I believe my contributions has opened a broad venue for new MM structures based on PnBG structures with superior characteristics compared to the conventional devices.

Made available in DSpace on 2014-12-17T14:55:43Z (GMT). No. of bitstreams: 1 HumbertoDA_DISSERT.pdf: 1369294 bytes, checksum: 4b7817dfceebc22263e36739d877c8f2 (MD5) Previous issue date: 2010-06-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Recently, planar antennas have attracted interest due to its characteristics as well as the advantages they offer compared to other types of antennas. In the area of mobile communications the need for such antennas has become increasingly intense due to development, which requires antennas that operate in multifrequency and broadband. The microstrip antennas have narrow bandwidth due to losses in the dielectric caused by irradiation. Another limitation is the radiation pattern degradation due to generation of surface waves in the substrate. Some techniques are being developed to minimize this bandwidth limitation, as is the case in the study of type materials PBG - Photonic Band Gap, to compose the dielectric material. The analysis developed in this work were performed with use of the method LTT - Transverse Transmission Line, in the field of Fourier transform that uses a component propagating in the y direction (transerve real direction of propagation z), thus treating the general equations of the fields electric and magnetic fields as a functions of y E and Hy . This work has as main objective the method LTT structures resonator line slot with four layers of material photonic PBG, for obtaining the complex resonant frequency and efficiency of this structure. PBG theory is applied to obtain the relative permittivity for the substrate biases sep compounds photonic material. Numerical-computational results in graph form in two dimensions for all the analysis are presented for the proposed structures that have photonic materials, as substrates / Recentemente as antenas planares tem despertado interesses devido as suas caracter?sticas e vantagens que oferecem quando comparadas com os demais tipos de antenas. Na ?rea de comunica??es m?veis a necessidade de antenas desse tipo, tem se tornado cada vez mais utilizadas, devido ao intenso desenvolvimento, que necessita de antenas que operem em multifrequ?ncia e em banda larga. As antenas de microfita apresentam largura de banda estreita devido ?s perdas no diel?trico geradas pela irradia??o. Outra limita??o ? a degrada??o do diagrama de irradia??o devido ? gera??o de ondas de superf?cie no substrato. Algumas t?cnicas est?o sendo desenvolvidas para minimizar esta limita??o de banda, como ? o caso do estudo de materiais do tipo PBG Photonic Band Gap, para compor o material diel?trico. Este trabalho tem como objetivo principal a aplica??o do m?todo LTT ?s estruturas ressoadoras retangulares de fenda com quatro camadas de material fot?nico PBG, para a obten??o da freq??ncia de resson?ncia complexa e a efici?ncia de radia??o dessa estrutura. As an?lises desenvolvidas neste trabalho foram realizadas com utiliza??o do m?todo LTT Linha de Transmiss?o Transversa, no dom?nio da Transformada de Fourier que utiliza uma componente de propaga??o na dire??o y (transversa ? dire??o real de propaga??o z), tratando assim as equa??es gerais dos campos el?tricos e magn?ticos em fun??o de yEe yH. A teoria PBG ser? aplicada para a obten??o da permissividade relativa para as polariza??es s e p dos substratos compostos de material fot?nico. Resultados num?rico-computacionais s?o apresentados em forma de gr?fico em duas dimens?es para todas as an?lises realizadas para as estruturas propostas que tem como substratos, materiais fot?nicos

An innovative approach for characterization of one dimensional Photonic Band Gap structures comprised of metallic inclusions (i.e. subwavelength dipole elements or resonant ring elements) is presented. Through an efficient S- to T-parameters conversion technique, a detailed analysis has been performed to investigate the variation of the dispersion characteristics of 1-D PBG structures as a function of the cell element configuration. Also, for the first time, the angular sensitivity of the structure has been studied in order to obtain the projected band diagrams for both TE and TM polarizations. Polarization sensitivity of the subwavelength cell element is exploited to propose a novel combination of elements which allows achieving PBGs with simultaneous frequency and polarization selectivity. The proposed approach demonstrates that the dispersion characteristic of each orthogonal polarization can be independently adjusted with dipole elements parallel to that same polarization. Generally, the structure has potential applications in orthomode transducer, and generally whenever the polarization of the incoming signal is to be used as a means of separating it from another signal in the same frequency band that is of orthogonal polarization. The current distribution and the resonance behavior of the ring element is studied and the effect of resonance on dispersion characteristics of 1-D PBGs composed of rings is investigated for the first time, for both individual and coupled rings. Interestingly, it is observed that 1-D PBG composed of resonant elements consistently has a bandgap around the resonant frequency of the single layer structure.

No description available.