The refraction properties of photonic crystal lattices offers methods to control the beam steering of light through use of non-linear dispersion contours. In this thesis new photonic crystal structures, such as the square and triangular superlattices, that provide novel refractive properties are analyzed. The property difference between rows in these structures is the hole radius Δr. The difference in hole sizes leads to observation of the superlattice effect, that is, a change in the refractive index Δn between opposite rows of holes. The index difference becomes a function of the size of the smaller r2 hole area or volume due to the addition of the higher index background material compared to the larger r1 holes. The difference in hole radii Δr = r1 - r2 is referred to as the static superlattice strength and is designated by the ratio of r2/r1. The superlattice strength increases as the ratio of r2/r1 decreases. The hole size modulation creates modified dispersion contours that can be used to fabricate advanced beam steering devices through the introduction of electro-optical materials and a controlled bias. A discussion of these superlattice structures and their optical properties will be covered, followed by both static and dynamic tunable device constructions utilizing these designs. Also, static tuning of the devices through the use of atomic layer deposition, as well as active tuning methods utilizing liquid crystal (LC) infiltration, sealed LC cells, and the addition of electro-optic material will be discussed. Also in this thesis we present designs to implement a simpler demonstration of cloaking, the carpet cloak, in which a curved reflective surface is compressed into a flat reflective surface, effectively shielding objects behind the curve from view with respect to the incoming radiation source. This approach eliminates the need for metallic resonant elements. These structures can now be fabricated using only high index dielectric materials by the use of electron beam lithography and standard cleanroom technologies. The design method, simulation analysis, device fabrication, and near field optical microscopy (NSOM) characterization results are presented for devices designed to operate in the 1400-1600nm wavelength range. Improvements to device performance by the deposition/infiltration of linear, and potentially non-linear optical materials, were investigated.

Hybrid plasmonic-photonic structures were introduced as novel platforms for on-chip biochemical sensing and spectroscopy. By appropriate coupling of photonic and plasmonic modes, a hybrid architecture was realized that can benefit from the advantages of integrated photonics such as the low propagation loss, ultra-high Q modes, and robustness, as well as the advantages of nanoplasmonics such as extreme light localization, large sensitivities, and ultra-high field enhancements to bring about unique performance advantages for efficient on-chip sensing. These structures are highly sensitive and can effectively interact with the target biological and chemical molecules. It was shown that interrogation of single plasmonic nanoparticles is possible using a hybrid waveguide and microresonator-based structure, in which light is efficiently coupled from photonic structures to the integrated plasmonic structures. The design, implementation, and experimental demonstration of hybrid plasmonic-photonic structures for lab-on-chip biochemical sensing applications were discussed. The design goal was to achieve novel, robust, highly efficient, and high-throughput devices for on-chip sensing. The sensing scenarios of interest were label-free refractive index sensing and SERS. Nanofabrication processes were developed to realize the hybrid plasmonic-photonic structures. Silicon nitride was used as the material platform to realize the integrated photonic structure, and gold was used to realize plasmonic nanostructures. Special optical characterization setups were designed and implemented to test the performance of these nanoplasmonic and nanophotonic structures. The integration of the hybrid plasmonic-photonic structures with microfluidics was also optimized and demonstrated. The hybrid plasmonic-photonic-fluidic structures were used to detect different analytes at different concentrations. A complete course of research from design, fabrication, and characterization to demonstration of sensing applications was conducted to realize nanoplasmonic and integrated photonic structures. The novel structures developed in this research can open up new potentials for biochemical sensors with advanced on-chip functionalities and enhanced performances.

In this dissertation, high-power ytterbium-doped fiber amplifiers designed with advanced waveguide concepts are characterized and power scaled. Fiber waveguides utilizing cladding microstructures to achieve wave guidance via the photonic bandgap (PBG) effect and a combination of PBG and modified total internal reflection (MTIR) have been proposed as viable single-mode waveguides. Such novel structures allow larger core diameters (>35 μm diameters) than conventional step-index fibers while still maintaining near-diffraction limited beam quality. These microstructured fibers are demonstrated as robust single-mode waveguides at low powers and are power scaled to realize the thermal power limits of the structure. Here above a certain power threshold, these coiled few-mode fibers have been shown to be limited by modal instability (MI); where energy is dynamically transferred between the fundamental mode and higher-order modes. Nonlinear effects such as stimulated Brillouin scattering (SBS) are also studied in these fiber waveguides as part of this dissertation. Suppressing SBS is critical towards achieving narrow optical bandwidths (linewidths) necessary for efficient fiber amplifier beam combining. Towards that end, new effects that favorably reduce acoustic wave dispersion to increase the SBS threshold are discovered and reported. The first advanced waveguide examined is a Yb-doped 50/400 µm diameter core/clad PBGF. The PBGF is power scaled with a single-frequency 1064 nm seed to an MI-limited 410 W with 79% optical-to-optical efficiency and near-diffraction limited beam quality (M-Squared < 1.25) before MI onset. To this author's knowledge, this represents 2.4x improvement in power output from a PBGF amplifier without consideration for linewidth and a 16x improvement in single-frequency power output from a PBGF amplifier. During power scaling of the PBGF, a remarkably low Brillouin response was elicited from the fiber even when the ultra large diameter 50 µm core is accounted for in the SBS threshold equation. Subsequent interrogation of the Brillouin response in a pump probe Brillouin gain spectrum diagnostic estimated a Brillouin gain coefficient, gB, of 0.62E-11 m/W; which is 4x reduced from standard silica-based fiber. A finite element numerical model that solves the inhomogenous Helmholtz equation that governs the acoustic and optical coupling in SBS is utilized to verify experimental results with an estimated gB = 0.68E-11 m/W. Consequently, a novel SBS-suppression mechanism based on inclusion of sub-optical wavelength acoustic features in the core is proposed. The second advanced waveguide analyzed is a 35/350 µm diameter core/clad fiber that achieved wave guidance via both PBG and MTIR, and is referred to as a hybrid fiber. The waveguide benefits mutually from the amenable properties of PBG and MTIR wave guidance because robust single-mode propagation with minimal confinement loss is assured due to MTIR effects, and the waveguide spectrally filters unwanted wavelengths via the PBG effect. The waveguide employs annular Yb-doped gain tailoring to reduce thermal effects and mitigate MI. Moreover, it is designed to suppress Raman processes for a 1064 nm signal by attenuating wavelengths > 1110 nm via the PBG effect. When seeded with a 1064 nm signal deterministically broadened to ~1 GHz, the hybrid fiber was power scaled to a MI-limited 820 W with 78% optical-to-optical efficiency and near diffraction limited beam quality of M_Squared ~1.2 before MI onset. This represents a 14x improvement in power output from a hybrid fiber, and demonstrates that this type of fiber amplifier is a quality candidate for further power scaling for beam combining.

Hybrid microstructured fibers, utilizing both air holes and high index cladding structures, provide important advantages over conventional fiber including robust fundamental mode operation with large core diameters (>30 mu m) and spectral filtering (i.e. amplified spontaneous emission and Raman suppression). This work investigates the capabilities of a hybrid fiber designed to suppress stimulated Brillouin scattering (SBS) and modal instability (MI) by characterizing these effects in a counter-pumped amplifier configuration as well as interrogating SBS using a pump-probe Brillouin gain spectrum (BGS) diagnostic suite. The fiber has a 35 mu m annularly gain tailored core, the center doped with Yb and the second annulus comprised of un-doped fused silica, designed to optimize gain in the fundamental mode while limiting gain to higher order modes. A narrow-linewidth seed was amplified to an MI-limited 820 W, with near-diffraction-limited beam quality, an effective linewidth similar to 1 GHz, and a pump conversion efficiency of 78%. Via a BGS pump-probe measurement system a high resolution spectra and corresponding gain coefficient were obtained. The primary gain peak, corresponding to the Yb doped region of the core, occurred at 15.9 GHz and had a gain coefficient of 1.92x10(-11) m/W. A much weaker BGS response, due to the pure silica annulus, occurred at 16.3 GHz. This result demonstrates the feasibility of power scaling hybrid microstructured fiber amplifiers

No description available.

Los efectos de la luz lenta y luz rápida (SFL) han mostrado unas capacidades excepcionales sobre el control dinámico de la velocidad de la luz en diferentes medios. Una de las motivaciones más estimulantes redica en la potente aplicación de estos sistemas en el marco del procesado fotónico de señales de radio frecuencia (RF). En esta tesis doctoral, se evalúan las prestaciones de las plataformas de SFL actuales para desarrollar múltiples tareas que se requieren en el campo de la fotónica de microondas (MWP) con el valor añadido de sintonizabilidad y operación en banda ancha. En esta contexto, el scattering de Brillouin estimulado (SBS) tanto en fibra estándar como en fibra mantenedora de polarización (PMF), de redes Bragg (FBG), amplificadores ópticos de semiconductor (SOA) y cristales fotónicos (PhC) han sido las tecnologías bajo estudio. Desde escalas del orden de km hata mm, estas plataformas de SFL representan la evolución hacia la consolidación de componentes y subsistemas de MWP en circuitos fotónicos integrados (PIC). Diversos modelos analíticos y numéricos se han desarrollado con el objetivo de entender los procesos físicos que goboernan la porpagación a través de las diferentes plataformas de SFL, así como para describir los enfoques de MWP propuestos. Además, a través de las plataformas presentadas se ha llevado a cabo el análisis de las prestaciones de dos de las funcionalidades clave que se requieren para el procesado fotónico de señales de microondas, desfasadores sintonizables y retardos verdaderos (TTD). Se ha propuesto un sistema de TTD basado en la llamada técnica de sintonización separada de la portadora (SCT) a través de los efectos de SBS en fibrras estándr. Se ha evaluado la interacción del SBS en PMF con el propósito de desarrollar redes de Brillouin dinámicas (DBG), cuya fase generada ha sido fruto de estudio. Por otro lado, también se ha demostrado un sistema de densado distribuido basado en la reflexión continua de un pulso estrecho a lo la / Sancho Durá, J. (2012). Photonic-assisted RF Signal Processing based on Slow and Fast Light Technological Platforms [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/16471 / Palancia

Researchers have argued for many years that one of the conditions for omnidirectional reflection in a one-dimensional photonic crystal is a strong refractive index contrast between the two constituent dielectric materials. Using numerical simulations and the theory of Anderson localization of light, in this work we demonstrate that an omnidirectional band gap can indeed be created utilizing low refractive index contrast materials when they are arranged in a disordered manner. Moreover, the size of the omnidirectional band gap becomes a controllable parameter, which now depends on the number of layers and not only on the refractive index contrast of the system, as it is widely accepted. This achievement constitutes a major breakthrough in the field since it allows for the development of cheaper and more efficient technologies. Of particular interest is the case of high index contrast one-dimensional photonic crystal fibers, where the propagation losses are mainly due to increased optical scattering from sidewall roughness at the interfaces of high index contrast materials. By using low index contrast materials these losses can be reduced dramatically, while maintaining the confinement capability of the waveguide. This is just one of many applications that could be proven useful for this discovery.

In this dissertation, I am presenting my research on the fabrication and simulation of the optical properties of 3D photonic crystals and 2D graded photonic super-crystals. The 3D photonic crystals were fabricated using holographic lithography with a single, custom-built reflective optical element (ROE) and single exposure from a visible light laser. Fully 3D photonic crystals with 4-fold, 5- fold, and 6-fold symmetries were fabricated using the flexible, 3D printed ROE. In addition, novel 2D graded photonic super-crystals were fabricated using a spatial light modulator (SLM) in a 4f setup for pixel-by-pixel phase engineering. The SLM was used to control the phase and intensity of sets of beams to fabricate the 2D photonic crystals in a single exposure. The 2D photonic crystals integrate super-cell periodicities with 4-fold, 5-fold, and 6-fold symmetries and a graded fill fraction. The simulations of the 2D graded photonic super-crystals show extraordinary properties such as full photonic band gaps and cavity modes with Q-factors of ~106. This research could help in the development of organic light emitting diodes, high-efficiency solar cells, and other devices.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18284号 / 工博第3876号 / 新制||工||1595(附属図書館) / 31142 / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 野田 進, 教授 川上 養一, 教授 藤田 静雄 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

We have invented an in-plane all-photonic transduction method for photonic microcantilever arrays that is scalable to large arrays for sensing applications in both bio- and nanotechnology. Our photonic transduction method utilizes a microcantilever forming a single mode rib waveguide and a differential splitter consisting of an asymmetric multimode waveguide and a Y-branch waveguide splitter. The differential splitter's outputs are used to form a differential signal that has a monotonic response to microcantilever deflection. A differential splitter using an amorphous silicon strip-loaded multimode rib waveguide is designed and fabricated to demonstrate the feasibility of the in-plane photonic transduction method. Our initial implementation shows that the sensitivity of the device is 0.135×10^-3 nm^-1 which is comparable to that of other readout methods currently employed for static-deflection based sensors. Through further analysis of the optical characteristics of the differential splitter, a new asymmetric double-step multimode rib waveguide has been devised for the differential splitter. The new differential splitter not only improves sensitivity and reduces size, but also eliminates several fabrication issues. Furthermore, photonic microcantilever arrays are integrated with the differential splitters and a waveguide splitter network in order to demonstrate scalability. We have achieved a measured sensitivity of 0.32×10^-3 nm^-1, which is 2.4 times greater than our initial result while the waveguide length is 6 times shorter. Analytical examination of the relationship between sensitivity and structure of the asymmetric double-step rib waveguide shows a way to further improve performance of the photonic microcantilever sensor. We have demonstrated experimentally that greater sensitivity is achieved when increasing the step height of the double-step rib waveguide. Moreover, the improved sensitivity of the photonic microcantilever system, 0.77×10^-3 nm^-1, is close to the best reported sensitivities of other transduction methods (~10^-3 nm^-1).