Thesis (Ph. D.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains xiii, 109 p. : ill. Includes abstract. Includes bibliographical references (p. 102-109).

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 132-142).

Thesis (Ph. D.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains xiii, 150 p. : ill. Includes abstract. Includes bibliographical references (p. 141-150).

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.

Although the study of the interaction of acoustic and elastic waves with periodic surfaces and structures has a rich history dating back to Lord Rayleigh, it has recently been attracting new research efforts due to its value in the study of phononic crystals and in methods for ultrasonic non-destructive evaluation (NDE). The objective of the research described in this thesis is to provide new numerical and experimental tools capable of capturing important features that occur due to the diffraction of ultrasound on periodic solid surfaces. This thesis is divided into four main parts. First, the Rayleigh-Fourier (R-F) method will be used to simulate diffracted fields generated by structures containing multiple periodic surfaces and/or multiple solid layers. The second part of this thesis examines diffraction effects and compares ultrasonic NDE techniques for surfaces with imperfect periodicities. The third portion of this thesis focuses on one unusual phenomenon that has been observed on periodic surfaces, namely the lateral backward displacement of a bounded ultrasonic beam along the surface. This effect is currently understood to occur due to backward propagating surface waves that result from diffraction and mode conversion on the surface. The fourth and final part of this thesis describes the diffraction of bulk ultrasonic waves that can occur on the surfaces of phononic crystals.

CAPES / Com o intuito de agregar valor à literatura numa área onde resultados positivos são incentivadores no processo de continuidade de pesquisas nesta área, até que se consiga obter a necessária reprodutibilidade do processo para gravação de redes em fibras óticas micro-estruturadas, este trabalho mostra o sucesso obtido na gravação de redes de Bragg e redes de período longo em fibras de cristal fotônico de núcleo sólido. As redes de Bragg são gravadas em fibras micro-estruturadas de 12 anéis de furos ao redor do núcleo, dopado com uma pequena quantidade de germânio. A gravação destas redes é feita utilizando radiação ultravioleta (UV) do laser excímero KrF em 248 nm e máscara de fase, e são obtidas redes de Bragg de ≈ 11 dB de refletividade. As redes de período longo, por sua vez, são gravadas em fibras micro-estruturadas de sílica pura de 6 anéis de furos de ar ao redor do núcleo. Utilizando o método de gravação ponto-a-ponto e radiação infra-vermelha (IR) do laser CO2 são obtidas redes com resultados condizentes com a literatura, ou seja, redes de período longo com um modo principal de ressonância e perda na transmissão de até 17 dB. Também são detalhadas as caracterizações das redes de período longo quanto à tração mecânica e à temperatura, com o diferencial da repetibilidade de ambos os testes para maior confiabilidade nos resultados. Foram obtidas sensibilidade à tração entre −0, 85 pm/με e −6, 3 pm/με. Obtiveram-se sensibilidades à temperatura iguais a −18, 4 pm/◦ C e −19, 6 pm/◦ C. / In order to contribute to literature in an area where successful results are important in the process of further research in this area, until it can be obtained the necessary reproducibility of the process of writting gratings in micro-structured optical fibers, this work shows positive Bragg and long period gratings written in solid core photonic crystal fibers. The Bragg gratings are written in a 12 rings of holes around the core doped with a small amount of germanium micro-structured fiber. Written process of these gratings is made using ultraviolet excimer laser KrF at 248 nm and phase mask, and are obtained Bragg gratings with ≈ 11 dB reflectivity. Long period gratings, in turn, are written in micro-structured optical fibers made of pure silica 6 rings of air holes around the core. Using the method of point-to-point and infrared radiation CO2 laser are obtained gratings with consistent results within the literature, that is, gratings with a main mode of resonance and transmission loss of up to 17 dB. This work also detailed characterizations of long period gratings on mechanical stress and temperature variation, emphasizing the repeatability of both tests for more reliable results. Sensitivity to mechanical stress were obtained between −0, 85 pm/με and −6, 3 pm/με. More, sensitivities to temperature variation were equal to −18, 4 pm/◦ C and −19, 6 pm/◦ C.

CAPES / Com o intuito de agregar valor à literatura numa área onde resultados positivos são incentivadores no processo de continuidade de pesquisas nesta área, até que se consiga obter a necessária reprodutibilidade do processo para gravação de redes em fibras óticas micro-estruturadas, este trabalho mostra o sucesso obtido na gravação de redes de Bragg e redes de período longo em fibras de cristal fotônico de núcleo sólido. As redes de Bragg são gravadas em fibras micro-estruturadas de 12 anéis de furos ao redor do núcleo, dopado com uma pequena quantidade de germânio. A gravação destas redes é feita utilizando radiação ultravioleta (UV) do laser excímero KrF em 248 nm e máscara de fase, e são obtidas redes de Bragg de ≈ 11 dB de refletividade. As redes de período longo, por sua vez, são gravadas em fibras micro-estruturadas de sílica pura de 6 anéis de furos de ar ao redor do núcleo. Utilizando o método de gravação ponto-a-ponto e radiação infra-vermelha (IR) do laser CO2 são obtidas redes com resultados condizentes com a literatura, ou seja, redes de período longo com um modo principal de ressonância e perda na transmissão de até 17 dB. Também são detalhadas as caracterizações das redes de período longo quanto à tração mecânica e à temperatura, com o diferencial da repetibilidade de ambos os testes para maior confiabilidade nos resultados. Foram obtidas sensibilidade à tração entre −0, 85 pm/με e −6, 3 pm/με. Obtiveram-se sensibilidades à temperatura iguais a −18, 4 pm/◦ C e −19, 6 pm/◦ C. / In order to contribute to literature in an area where successful results are important in the process of further research in this area, until it can be obtained the necessary reproducibility of the process of writting gratings in micro-structured optical fibers, this work shows positive Bragg and long period gratings written in solid core photonic crystal fibers. The Bragg gratings are written in a 12 rings of holes around the core doped with a small amount of germanium micro-structured fiber. Written process of these gratings is made using ultraviolet excimer laser KrF at 248 nm and phase mask, and are obtained Bragg gratings with ≈ 11 dB reflectivity. Long period gratings, in turn, are written in micro-structured optical fibers made of pure silica 6 rings of air holes around the core. Using the method of point-to-point and infrared radiation CO2 laser are obtained gratings with consistent results within the literature, that is, gratings with a main mode of resonance and transmission loss of up to 17 dB. This work also detailed characterizations of long period gratings on mechanical stress and temperature variation, emphasizing the repeatability of both tests for more reliable results. Sensitivity to mechanical stress were obtained between −0, 85 pm/με and −6, 3 pm/με. More, sensitivities to temperature variation were equal to −18, 4 pm/◦ C and −19, 6 pm/◦ C.

Saccharides, a class of organic materials, are potential candidates for nonlinear optical applications. Ascorbic acid is a sugar acid and is classified as a monosaccharide. The molecule of ascorbic acid has two chiral centers and, therefore, four stereoisomers. Among them, two are naturally occurring compounds; L-ascorbic acid and D-isoascorbic acid. From these two acids various salts and other derivatives could be synthesized. In this thesis, four compounds of the ascorbic acid family were selected for detailed study based on their nonlinearity, chemical and physical stability and their crystallization characteristics. The thesis is organized into seven chapters. The first chapter covers the theoretical background of nonlinear optics, especially, second harmonic generation. Second chapter details the experimental techniques and methodology adopted. Chapter 3 discusses the crystal structure, growth, physical and nonlinear optical properties of Lithium Disoascorbate monohydrate (LDAM). Detailed analysis of refractive index measurements employing Brewsters angle method and determination of phase matching curves, effective nonlinear coefficient, walk off angle etc are given. In Chapter 4, investigations on Sodium D-isoascorbate monohydrate (NDAM) are presented. Detailed characterization of the crystals including thermal, optical, dielectric properties are carried out. Analyses of dielectric dispersion based on Cole-Cole equation are discussed. Comprehensive studies on laser damage of the crystals are discussed. Chapter 5 discusses the nonlinear optical properties of the monoclinic D-isoascorbic acid (DIA). Chapter 6 presents studies on the triclinic Lithium L-ascorbate dihydrate (LLA) crystals. The crystals exhibit intense non-collinear second harmonic rings as they possesses large birefringence coupled with high second order nonlinear coefficients. The SHG conversion efficiency of these crystals is 15 times that of KDP. In the final chapter, a comprehensive summary of the work carried out is presented along with scope for further investigations.