The incorporation of porosity in a material potentially results in the changes in electrical, mechanical and electrical properties and has generated much interest by researchers. The development of new techniques for inducing porosity in thin films may prove advantageous if they lead to a decrease in processing complexity, or an increase in the processing flexibility by widening the window of compatible physical conditions, or the improvement of the final properties of the porous materials. Two processing techniques were developed to produce porosity in thin dielectric films at temperatures below the glass transition temperature of the host matrix. These glassy-regime processing methods relied on the susceptibility of hydrogen silsesquioxane (HSQ) to gelation in the glassy regime when exposed to polar substances. Both of these glassy-regime processing methods relied on the susceptibility of hydrogen silsesquioxane (HSQ) towards gelation in the glassy regime when exposed to polar substances. The first processing method made use of co-solvent mixtures of polar non-protic organic solvent to serve both as gelation catalysts and pore-generators. HSQ films were soaked in the polar organic co-solvents, which penetrated the films and initiated crosslinking throughout the matrix. Afterwards the films were baked, volatilizing entrapped solvents and producing air pockets within the rigid matrix. The second porosity method used UV-radiation to initiate acid-catalyzed decomposition of polycarbonate sacrificial polymers after first using bases to catalyze the gelation of HSQ. The radiation-based (direct-write) decomposition of the porogen enabled the selective patterning of regions porosity via the use of a photomask, which resulted in the creation of refractive index profiles in the direct-written films. Porous films that were produced by these two glassy-state processing techniques were used to build slab waveguide structures. Optical characterization experiments showed that the fabricated waveguides had average propagation losses of 16 - 27 dB/cm for the first guided TE mode and about 36-40 dB/cm, for the second TE guided mode. It is believed that the large propagation loss values were caused by a combination of the Rayleigh scattering from the relatively large UV-induced pores produced in the direct-write layers as well as scattering induced by surface roughness.

In high performance electronic systems, with increasing chip speed and larger number of processors, the system performance is being limited by off-chip metal interconnects. In such systems, polymer optical waveguides are being considered to replace electrical interconnects because of their high capacity for bandwidth and less constraints on interconnect length. The optical loss in the polymer optical waveguides is the key criterion used to evaluate their performance, and is significantly affected by thermal curing and aging. The evolution of degree-of-cure is determined from differential scanning calorimetry and compared to optical absorption from spectroscopy. Optical loss due to scattering mechanisms is related to local density fluctuations, which is studied using dielectric analysis. Based on the optical loss trends in uncladded and cladded waveguides, the underlying mechanisms for the optical loss variations are proposed and a cure process schedule to realize the lowest optical loss is recommended. Process-induced thermal stresses can also affect the polymer waveguide by introducing stress birefringence. The stress-optical coefficients of the siloxane polymer are extracted and employed in a numerical modeling method to determine the stress-induced birefringence in an optical waveguide system. The thermal-aging dependent optical loss is determined for waveguide samples at several different accelerated temperature conditions. To get the field-use conditions, the temperature distribution in the vicinity of the embedded laser and the polymer waveguide is determined. Using such thermal experimental data, the analytical reliability models were employed to relate the optical loss with time, and provide a practical way of determining whether the optical waveguides would perform within the optical loss budget during field-use conditions.

<p>The rapid expansion of major cities in the west Europeancountries has accentuated the need to exploit every potentialsite for new establishments, e.g. areas over train tunnels andnear railway tracks in general. A significant impediment toexploit such areas is the structure-borne noise generated bythe train traffic, which is transmitted into buildings via theground. Reliable prediction methods and cost-effective noisecontrol measures are therefore needed and are also the objectof the present work. In this thesis, the studied buildings areconsidered as wave-guides for the sound transmitted from theground. The work is restricted to the case of hard ground suchas granite. The chosen technique permits comparison betweendifferent potential measures to reduce the transmission ofstructure-borne sound upward in buildings. It is shown that thedesign of the load-bearing structures is important in thiscontext, and a design with relocated columns has givenpromising results. It is also shown that the stiffness of theground plays an important role in the transmission process.This leads to the idea that a sand layer between the foundationof the building and the bedrock may reduce the transmission.New methods have thus been developed in the course of this workto evaluate the stiffness of the layer using approximate andexact techniques. Results are presented and a comparison ismade with previous results for a "normal" building and it isshown that the insertion of sand layer has a potential toconsiderably reduce the sound level in the building.</p><p><b>Keywords:</b>Ground-borne noise, railway noise, in-planewaves, wave-guides, scattering, propagation constant, inputmobility, elastic stratum, dual integral equations.</p>

The time required for inspection and maintenance of piping systems and vessels needs to be reduced to both minimize down time and decrease operational costs of petrochemical plants. Current ultrasonic inspection systems are not suited for on-line monitoring, with the main issues being the resistance of transducers and their coupling to high temperatures and the removal of insulation to access structures. The use of welded cylindrical rods is thus proposed, but measurements are threatened by "trailing echo" generation in waveguides. The introduction of a taper angle is investigated to attenuate these undesired echoes. While clean signals can always be obtained by increasing the taper angle in long rods, that is not always the case for short rods, which are considered here. In addition, temperature variations have a non-negligible impact on the arrival time of the backwall echo when performing measurements with a waveguide, and on-line compensation is essential. Since the interface echo between the rod and the pipe wall may be suppressed after the welding operation, a notch is machined at the end of the rod to create a reflected echo, which can be used for on-line compensation. Finally, the implementation of waveguides is considered for both pulse-echo and pitch-catch modes. In the pitch-catch mode, the backwall echo and the notch echo are received by different transducers and signals of interst are both first arrivals. As a result, trailing echoes do not impede measurements and their attenuation becomes unnecessary. In contrast, pulse-echo measurements are sensitive to trailing echoes and the waveguide's design plays an essential role in the feasibility of measurements. However, the environment also imposes a set of constraints on waveguide dimensions that complicates the implementation of pulse-echo measurements. Being more flexible, the pitch-catch configuration is chosen for final implementation. Experiments are performed to verify the concept feasibility, and the accuracy of measurements with thickness and temperature changes is also confirmed.

The main objective of this research is to fabricate and characterize an optically integrated interferometric sensor on standard silicon and silicon CMOS circuitry. An optical sensor system of this nature would provide the high sensitivity and immunity to electromagnetic interference found in interferometric based sensors in a lightweight, compact package capable of being deployed in a multitude of situations inappropriate for standard sensor configurations. There are several challenges involved in implementing this system. These include the development of a suitable optical emitter for the sensor system, the interface between the various optically embedded components, and the compatibility of the Si CMOS with heterogeneous integration techniques. The research reported outlines a process for integrating an integrated sensor on Si CMOS circuitry using CMOS compatible materials, integration techniques, and emitter components.

Thesis, (M.E.?)-- University of Adelaide, Dept. of Engineering, 1958. / Typewritten.

Orientador: Hugo Enrique Hernandez Figueroa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-21T13:36:44Z (GMT). No. of bitstreams: 1 RubioNoriega_RuthEsther_M.pdf: 3183170 bytes, checksum: af9b79df81c18d5376bdcda8ca9f973a (MD5) Previous issue date: 2012 / Resumo: A principal contribuição deste trabalho _e a proposta da análise de estruturas periodicamente segmentadas na plataforma de silício sobre isolante (SoI), usando o método dos elementos finitos em um domínio computacional de duas dimensões...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital / Abstract: The principal contribution of this work is to propose the analysis of grating periodic structures on the silicon-on-insulator platform through the finite element method in a two dimension computational domain...Note: The complete abstract is available with the full electronic document / Mestrado / Telecomunicações e Telemática / Mestra em Engenharia Elétrica

The objective of this research is to investigate the use of laser direct writing to micro-pattern low loss passive optical channel waveguide devices using a new hybrid organic/inorganic polymer. Review of literature shows previous methods of optical waveguide device patterning as well as application of other non-polymer materials. System setup and design of the waveguide components are discussed. Results show that laser direct writing of the hybrid polymer produce single mode interconnects with a loss of less 1dB/cm.

Bound state systems consisting of three nonrelativistic particles are numerically studied. Calculations are performed employing two-body and three-body forces as input in the Hamiltonian in order to study the role or contribution of three-body forces to the binding in these systems. The resulting differential Faddeev equations are solved as three-dimensional equations in the two Jacobi coordinates and the angle between them, as opposed to the usual partial wave expansion approach. By expanding the wave function as a sum of the products of spline functions in each of the three coordinates, and using the orthogonal collocation procedure, the equations are transformed into an eigenvalue problem. The matrices in the aforementioned eigenvalue equations are generally of large order. In order to solve these matrix equations with modest and optimal computer memory and storage, we employ the iterative Restarted Arnoldi Algorithm in conjunction with the so-called tensor trick method. Furthermore, we incorporate a polynomial accelerator in the algorithm to obtain rapid convergence. We applied the method to obtain the binding energies of Triton, Carbon-12, and Ozone molecule. / Physics / M.Sc (Physics)

In the past decade, great research effort was inspired by the need to realise active optical functionalities in silicon, in order to develop the full potential of silicon as a photonic platform. In this thesis we explore the possibility of achieving tunable delay and optical gain in silicon, taking advantage of the unique dispersion capabilities of photonic crystals. To achieve tunable optical delay, we adopt a wavelength conversion and group velocity dispersion approach in a miniaturised engineered slow light photonic crystal waveguide. Our scheme is equivalent to a two-step indirect photonic transition, involving an alteration of both the frequency and momentum of an optical pulse, where the former is modified by the adiabatic tuning possibilities enabled by slow light. We apply this concept in a demonstration of continuous tunability of the delay of pulses, and exploit the ultrafast nature of the tuning process to demonstrate manipulation of a single pulse in a train of two pulses. In order to address the propagation loss intrinsic to slow light structures, with a prospect for improving the performance of the tunable delay device, we also investigate the nonlinear effect of stimulated Raman scattering as a means of introducing optical gain in silicon. We study the influence of slowdown factors and pump-induced losses on the evolution of a signal beam along the waveguide, as well as the role of linear propagation loss and mode profile changes typical of realistic photonic crystal structures. We then describe the work conducted for the experimental demonstration of such effect and its enhancement due to slow light. Finally, as the Raman nonlinearity may become useful also in photonic crystal nanocavities, which confine light in very small volumes, we discuss the design and realisation of structures which satisfy the basic requirements on the resonant modes needed for improving Raman scattering.