The analogy of optical system to other physical systems has been attracting much attention over the past decades. In coupled optical lattices, phenomena originated from electronic systems, such as Bloch oscillations, Dynamic localization and Zener tunneling, have been extensively investigated and led to novel research directions and applications. Following this idea, harmonic oscillations are spatially mimicked by the propagation of supermodes in quadratically-coupled waveguide arrays. By analyzing the field envelope with the propagation constants and the superposition of the supermodes, we achieve conjugate-imaging at the half-period plane and self-imaging at the full-period plane, which give rise to the linear switching. Combining the linear switching and the nonlinear light propagation triggered at high power level, we demonstrate the superior performances of nonlinear power switching compared with traditional nonlinear directional couplers. Through the linear and nonlinear observation on AlGaAs waveguide array, we present the first experimental proof of the harmonic oscillations in optical waveguide arrays.

The study and applications of surface plasmon polaritons (SP) – also known as plasmonics – has attracted the interest of a wide range of researchers in various fields such as biology, physics, and engineering. Unfortunately, the large propagation losses of the SP severely limit the usefulness of plasmonics for many practical applications. In this dissertation a new wave guiding mechanism is proposed in order to address the large propagation losses of the plasmonic guides. Possible applications of this guiding scheme are also investigated. The proposed hybrid plasmonic waveguide (HPWG) consists of a metal layer separated from a high index slab by a low index spacer. A detailed analysis is carried out to clarify the wave guiding mechanism and it is established that the mode guided by the HPWG results from the coupling of a SP mode and a dielectric waveguide mode. A two dimensional HPWG is proposed and the effects of various parameters on the HPWG performance are analyzed in detail. This structure offers the possibility of integrating plasmonic devices on a silicon platform. The proposed waveguide supports two different modes: a hybrid TM mode and a conventional TE mode. The hybrid TM mode is concentrated in the low index layer, whereas the conventional TE mode is concentrated in the high index region. This polarization diversity is used to design a TM- and a TE-pass polarizer and a polarization independent coupler on a silicon-on-insulator (SOI) platform. Moreover, the performance of a HPWG bend is investigated and is compared with plasmonic waveguide bends. The proposed devices are very compact and outperform previously reported designs. The application of HPWG for biosensing is also explored. By utilizing the polarization diversity, the HPWG biosensor can overcome some of the limitations of plasmonic sensors. For example, unlike plasmonic sensors, the HPWG biosensor can remove the interfering bulk and surface effects.

Approved for public release; distribution is unlimited / A general study of conductor backed coplanar waveguide is presented. The impedance (Z(0)) and effective dielectric constant (ɛ(reff)) of conductor-backed coplanar waveguide (CBCPW) have been calculated by using a variational method and the boundary point matching method. In this present work only the TEM dominant low frequency propagation mode of coplanar line has been considered. Experimental facilities are vector network analyzer (HP8409) and bench-instrument measurements. / http://archive.org/details/evaluationofcopl00jeon / Captain, Korean Air Force

An ever-increasing demand for wider bandwidths in communication, radar, and imaging systems has emerged. In order to facilitate this growing demand, progressive research into millimeter-wave technologies has become vital in achieving next generation networks such as 5G. Being cost effective and easy to manufacture, Substrate Integrated Waveguide (SIW) circuits have been demonstrated as a viable candidate for high-frequency applications due to their low-loss, high quality-factor, and high power-handling capabilities.Research on beam-forming networks, specifically the Butler matrix, has demonstrated powerful beam-steering capabilities through the use of passive component networks. Through these clever configurations, a cost effective and robust option is available for us to use. In order to further millimeter-wave research in this area, this thesis presents a modified configuration of the Butler Matrix in SIW that is physically reconfigurable; by separating the Butler matrix from the antenna array at a pre-selected point, the array can be easily interchanged with other 1-Dimensional,and 2-Dimensional slot antenna arrays. Although this system does not fall under the rigorous definitions of Reconfigurable Antennas, it should be noted that the interchangeability of 1 and 2 dimensional arrays is not typically expressed in Butler matrix configurations. Design and simulations are carried out in CST Microwave Studio to inspect individual components as well as system characteristics. Circuit prototypes are then manufactured and tested in an anechoic chamber to validate simulation results and the design approach. / Graduate / 2020-07-17

A theoretical and experimental investigation into the use of the corrugated circular waveguide as a feeder and radiator for microwave antennas is described. Because corrugated waveguide feeders are ·overmoded, the effects on the propagation and radiation characteristics of mode conversion due to bends are investigated. New methods of providing higher order mode suppression are described, and substantiated by experimental results using resonant cavity and transmission line methods. The cross-polarisation properties of corrugated waveguides are shown to be intrinsically superior to those of smooth wall waveguides when the waveguide wall suffers elliptical deformation. As an alternative to the problems involved in overmoded operation a design of corrugated circular waveguide for HEll mono-mode operation, which still exhibits an attenuation advantage, is developed. The radiated co-polar and cross-polar performance of corrugated circular waveguides and narrow flare-angle corrugated concial horns are studied both experimentally and theoretically using a more accurate analysis than attempted by previous authors. Design curves for optimum cross-polar radiation performance are presented and a new method of improving the cross-polarisation performance of these structures is theoreti6ally predicted, and experimentally verifjed.

Freestanding self-written polymer waveguides were fabricated between two single mode fibres by using free radical photopolymerization technique. Photo curing enables modification of the initial liquid monomer at the illuminated part of the photopolymerizable system to form a permanent solid polymer waveguide between the cores of the fibres. Three compound acrylate based monomer (PETA) and Norland optical adhesives (NOA) were used to fabricate polymer bridges. The two systems are cured by visible and UV respectively. The optical, mechanical and nonlinearity properties of freestanding self-written polymer waveguides were investigated. Polymer waveguides up to 600 μm long between two fibres were fabricated by unidirectional illumination. The optical power required for photopolymerization is sufficiently low that it is possible to use incoherent light source instead of laser, which also allows investigation of the optical transmission over a wide range of wavelengths from visible to NIR. Optical characterization showed that PETA waveguides have better optical transmission and insertion loss of about 1.2 dB was measured for the bridges up to 600 μm long at 1550nm. Some limitations prevented us to extend waveguide’s length beyond 600 μm, the bridges also showed poor adhesion quality particularly at the polymer/fibre interfaces which needed an action. In order to improve mechanical properties of polymer waveguides also to overcome bonding failure between fibre and polymer, the fibres were treated with adhesion promoter. The treatment together with bidirectional curing from both fibres improved mechanical and optical properties of the polymer waveguides. The insertion loss was reduced to 0.6 dB associated with bi-directionally cured 600 μm long waveguide. Nonlinear response of polymer waveguides was measured by coupling a high power ultra short pulse laser. Using bidirectional curing and inserting fibre ends into capillaries millimeter long waveguides with minimum loss of 1.1dB were fabricated. A long interaction length of polymer waveguide allows spectral broadening and self-phase modulation features to occur in response to the high power laser propagation through the polymer bridge. The spectral broadening in polymer waveguide was much broader than that of 1.5m plain fibre. The comparison of the results associated with maximum phase shift occurs in polymer with plain fibre revealed that the nonlinear coefficient of polymer material is about 1000 times larger than that of silica fibre.

Researchers at Brigham Young University (BYU) have developed an optical biosensor that can quickly analyze a sample to detect any type of nucleic acid based organism, such as viruses or bacteria. The biosensor's reliability over time is compromised due to water absorbing into the SiO2 waveguides of the chip. It was hypothesized that keeping the thin-film stress of the waveguides close to zero would slow or stop water absorption from occurring. Completion of this thin-film study relied upon a new plasma enhanced chemical vapor deposition (PECVD) machine and a new 3-D optical profilometer, both of which were installed in the BYU cleanroom. The new PECVD machine was much more capable than previous machines at controlling deposition parameters and was a critical component in accurately controlling the intrinsic stress of deposited films. The 3-D optical profilometer provided us a way to accurately measure the intrinsic stress of the films. Rib waveguides made from different stressed SiO2 films were fabricated over anti-resonant reflecting optical waveguide (ARROW) layers. The wafers were baked out, cleaved, and their initial throughputs recorded. All waveguides were placed in a humid environment and were removed periodically to check their optical throughput. The resulting measurements were normalized to the highest measured throughput to determine how throughput was changing over time. Rib waveguides with the lowest stressed SiO2 had the slowest rate of throughput change, dropping to 50% of the original throughput after 40 days in the humid environment. The +50 MPa stressed waveguides performed next best, dropping to 20% of the original throughput after 40 days. The +100 MPA stressed waveguides dropped to 20% throughput after 16 days while the -50 MPa stressed wafers dropped to 20% optical throughput after 7 days. Keeping the stress of the film as low as possible helped reduce the rate of water absorption, but did not eliminate it completely. A method involving the use of high index difference buried channel waveguides is shown to be effective at stopping the effects of water absorption in our waveguides.

Long path optical waveguides can be used in optical absorption measurements to increase the optical path length and, thus, the overall absorption of a sample. Recently, 1m long coiled Liquid Waveguide Capillary Cells (LWCC) have been used by analytical spectroscopists to measure the absorption strength of weakly absorbing liquids. However, most of these measurements have used conventional light sources such as Xenon or Halogen lamps and not spectroscopic laser sources. In this thesis study, we used a LWCC absorption waveguide and a laser light source to measure, for the first time to our knowledge, the optical transmission through several water or liquid samples. It was found upon using the LWCC waveguide, the coherent laser light source tended to produce larger variability (>±15%) in the measurements of transmission readings than that for a conventional absorption cell or a conventional light source. This was especially evident when the LWCC waveguide was chemically cleaned with an acid and a base solution between each sample run as directed by the manufacturer. The non-coherent optical sources, Halogen lamp and Xenon arc lamp, produced more stable (±3%) transmission measurements. Finally, using a Helium Neon laser scattered off a diffuse reflecting surface was found to produce moderate variability (±7%), but this was much less than the coherent Helium Neon laser alone. It was concluded that the use of the coherent source was more susceptible than the non-coherent source to small changes in the reflectivity or index of refraction along the wall of the coiled LWCC waveguide. Our results are consistent with recent work by Barwicz and Haus, and by Lytle and Splawn who saw a large dependence of the transmission through a hollow straight waveguide upon changes in the polarization and input angle of the laser beam directed into the waveguide.

In the past decade, ultrashort laser sources have had a decisive impact on material processing for photonic applications. The technique is usually restricted to the elemental association of an ultrashort source with a focusing lens. It is thus limited in the achievable bulk modifications. Accompanying studies of material modifications in space and time, we propose here that automated spatio-temporal tailoring of the laser pulses is an efficient manner to overcome these limitations. More precisely, we demonstrate the generation of multiple processing foci for synchronous photomachining of multiple devices in the bulk. Thus, we report on the parallel photowriting of waveguides, light couplers, light dividers in 2D/3D in fused silica glass. We show that the domain of photowriting can be extended to deep focusing. We indicate that this can be achieved by wavefront shaping or temporal profile tailoring conducted by an evolutionary optimization loop. We also have unveiled a singular interaction regime where regular structuring takes place before the focal region. For the first time, the dynamics of the energy coupling to the glassy matrix is evaluated for various temporal pulse profiles. Enhanced energy confinement in the case of picosecond pulses is confirmed by characterization of the transient electronic gas and of the subsequent pressure. These pump-probe studies were carried out with a self-build time-resolved microscopy system with temporally shaped pump irradiation. We also developed a new method based on the Drude model to differentiate the electronic and matrix contributions to the contrast of the microscopy images.

Recent advances in computing technology have highlighted deficiencies with electrical interconnections at the motherboard and card-to-backplane levels. The CPU speeds of computing systems are drastically increasing with on-chip local clock speeds expected to approach 6 GHz by 2010. Yet, card-to-backplane communication speeds have been unable to maintain the same pace. At speeds beyond a few gigahertz the implementation of electronic interconnects gets increasingly complex, thus, alternative optical interconnection techniques are being extensively researched to relieve the expected CPU to data bus bottleneck. Despite the advantages afforded by optical interconnects there are still demands for improved packaging, enhanced signal tapping, and reduced cost expenditures. In this dissertation, we present a novel array waveguide evanescent coupling (AWEC) technology for card-to-backplane applications. The interconnection scheme is based on waveguide directional coupling between a backplane waveguide and a flexible waveguide connected to the access card or daughter board. To gain access to the shared bus media, coupling of evanescent waves is exploited to tap optical signals from the backplane waveguide to the corresponding card waveguide. The approach results in the elimination of micro-mirror out of plane deflectors and local waveguide termination obstacles present in other reported optical interconnect schemes. Most importantly, the AWEC method can yield efficient multi-drop bus architectures, not possible through free-space, fiber, or traditional guided wave approaches, that only achieve point-to-point topologies. The AWEC concept for optical interconnection was introduced through coupled mode theory, numerical simulations and BeamPROP aided CAD models. Subsequent experimental waveguide analysis was performed and shown to reasonably agree with the simulation results. Likewise, a high-resolution, cost-effective, and rapid prototyping approach for AWEC fabrication has been formulated. Significantly, when compared to other soft lithographic methods, the novel vacuum assisted microfluidic (VAM) technique results in improved waveguide structures, polymer background residue elimination and lower propagation losses. Moreover, experimental results show that our evanescent coupling approach facilitates high-speed coupling between card and backplane waveguides at speeds of 10 Gbps per channel; currently limited only by our testing electronics. In addition, satisfactory eye diagram performance comparable to that of a conventional fiber link, was also observed for the AWEC, alluding to possible aggregate speeds of 100 Gbps. Similarly, we implemented an elementary AWEC shared bus architecture and demonstrate a microprocessor-to-memory interconnect prototype through the proposed AWEC link. Notably, we expect that the AWEC scheme will be significant for high-speed optical interconnects in advanced computing systems.