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

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.

The growing speed and bandwidth requirements of telecommunication systems demand all-optical on-chip solutions. Microphotonic devices can deliver low power nonlinear signal processing solutions. This thesis looks at the slow light photonic crystals in chalcogenide glasses to enhance low power nonlinear operation. I demonstrate the development of new fabrication techniques for this delicate class of materials. Both, reactive ion etching and chemically assisted ion beam etching are investigated for high quality photonic crystal fabrication. A new resist-removal technique was developed for the chemical, mechanical and light sensitive thin films. I have developed a membraning method based on vapor phase etching in combination with the development of a save and economical etching tool that can be used for a variety of vapour phase processes. Dispersion engineered slow light photonic crystals in Ge₃₃As₁₂Se₅₅ are designed and fabricated. The demonstration of low losses down to 21±8dB/cm is a prerequisite for the successful demonstration of dispersion engineered slow light waveguides up to a group index of around n[subscript(g)] ≈ 40. The slow light waveguides are used to demonstrate highly efficient third harmonic generation and the first advantages of a pure chalcogenide system over the commonly used silicon. Ge₁₁.₅As₂₄24Se₆₄.₅ is used for the fabrication of photonic crystal cavities. Quality factors of up to 13000 are demonstrated. The low nonlinear losses have enabled the demonstration of second and third harmonic generation in those cavities with powers up to twice as high as possible in silicon. A computationally efficient model for designing coupled resonator bandpass filters is used to design bandpass filters. Single ring resonators are fabricated using a novel method to define the circular shape of the rings to improve the fabrication quality. The spectral responses of the ring resonators are used to determine the coupling coefficient needed for the design and fabrication of the bandpass filters. A flat top bandpass filter is fabricated and characterized as demonstration of this method. A passive all-optical regenerator is proposed, by integrating a slow-light photonic crystal waveguide with a band-pass filter based on coupled ring resonators. A route of designing the regenerator is proposed by first using the dispersion engineering results for nonlinear pulse propagation and then using the filter responses to calculate the nonlinear transfer function.

The field of nanophotonics is a major research topic, as it offers potential solutions to important challenges, such as the creation of low power, high bandwidth interconnects or optical sensors. Within this field, resonant structures and slow light waveguides are used to improve device performance further. Photonic crystals are of particular interest, as they allow the fabrication of a wide variety of structures, including high Q-factor cavities and slow light waveguides. The high scattering loss of photonic crystal waveguides, caused by fabrication disorder, however, has so far proven to be the limiting factor for device applications. In this thesis, I present a detailed study of propagation loss in slow light photonic crystal waveguides. I examine the dependence of propagation loss on the group index, and on disorder, in more depth than previous work by other authors. I present a detailed study of the relative importance of different components of the propagation loss, as well as a calculation method for the average device properties. A new calculation method is introduced to study different device designs and to show that photonic crystal waveguide propagation loss can be reduced by device design alone. These “loss engineered” waveguides have been used to demonstrate the lowest loss photonic crystal based delay line (35 dB/ns) with further improvements being predicted (< 20 dB/ns). Novel fabrication techniques were investigated, with the aim of reducing fabrication disorder. Initial results showed the feasibility of a silicon anneal in a nitrogen atmosphere, however poor process control led to repeatability issues. The use of a slow-fast-slow light interface allowed for the fabrication of waveguides spanning multiple writefields of the electron-beam lithography tool, overcoming the problem of stitching errors. The slow-fast-slow light interfaces were combined with loss engineering waveguide designs, to achieve an order of magnitude reduction in the propagation loss compared to a W1 waveguide, with values as low as 130 dB/cm being achieved for a group index around 60.

"Optical vortices are singularities in phase fronts of laser beams. They are characterized by a dark core whose size may dramatically affect their behavior upon propagation. Previously, only large-core vortices have been extensively studied. The object of the research presented in this dissertation was to explore ways of generating small-core optical vortices (also called optical vortex filaments), and to examine their propagation using analytical, numerical and experimental methods. Computer-generated holography enabled us to create arbitrary distributions of optical vortex filaments for experimental exploration. We used hydrodynamic paradigms to develop an heuristic model which described the dependence of vortex motion on other vortices and the background beam, both qualitatively and quantitatively. We predicted that pair of optical vortex filaments will rotate with angular rates inversely proportional to their separation distance (just like vortices in a fluid). We also reported the first experimental observation of this novel fluid-like effect. It was found, however, that upon propagation in linear media, the fluid-like rotation was not sustained owing to the overlap of diffracting vortex cores. Further numerical studies and experiments showed that rotation angle may be enhanced in nonlinear self-defocusing media. The results presented in this thesis offer us a better understanding of dynamics of propagating vortices which may result in applications in optical switching, manipulation of micro-particles and optical limiting."

"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."

Cette thèse est consacrée à l’étude du dépôt uniforme et de l’alignement à haute densité en nanotubes de carbone monoparois (NTCMP) sur différents substrats, à l’analyse qualitative des propriétés optiques excitoniques et aux modes de vibration des échantillons à NTCMP, et à la fabrication de guides d’onde optiques à base de NTCMP, en vue de composants photoniques pour les télécoms, autour de 1550 nm. Deux types de NTCMP ont été étudiés durant cette thèse : des NTCMP « HiPCO » (« high pressure carbon monoxide ») issus de la décomposition du monoxyde de carbone à haute pression, et des NTCMP « LV » (« laser vaporization ») provenant de l’ablation laser d’une cible en graphite. Plusieurs méthodes de dépôt de ces NTCMP ont été développées, telles que la méthode de dépôt assistée-par-tube, la méthode de dépôt en sillon, la méthode par pulvérisation, la méthode par centrifugation à grande vitesse, la méthode optimisée par centrifugation à vitesse réduite (MOCVR) et la méthode à jet d’encre. La qualité, l’épaisseur et l’uniformité des films de NTCMP sont caractérisées par observations au microscope électronique à balayage (MEB). Il est montré ici que l’uniformité des films à base de NTCMP HiPCO dépend fortement de la concentration en surfactants de la dispersion à base de NTCMP déposée. Des films uniformes de NTCMP LV ont été obtenus par la MOCVR et leur épaisseur couvre une gamme de 600nm à 900nm (avec une erreur <10%), qui dépend de la nature du substrat. L’alignement par diélectrophorèse (DEP) de NTCMP HiPCO et LV a été développé et optimisé. Ainsi, une nouvelle méthode (DEP « assistée-parchauffage ») est proposée afin d’obtenir un alignement à très haute densité en NTCMP. Cette méthode d’alignement par DEP assistée-par-chauffage a fait l’objet de travaux de simulation pour comprendre l’effet de la température. Les propriétés optiques excitoniques et les modes de vibration des NTCMP en solution et en film sur substrat ont été caractérisés par spectroscopies d’absorption, de photoluminescence (PL), d’excitation de la PL et Raman. Les niveaux de défauts et d’isolement des NTCMP HiPCO, les distributions en diamètre et en chiralité, les cartographies de l’uniformité et de l’épaisseur des films à base de NTCMP, et l’effet du laser à forte puissance, ont été qualitativement étudiés par spectroscopie Raman. Le rendement quantique interne en PL de NTCMP HiPCO en film est estimée à une valeur de 5%. Le transfert d’exciton entre NTCMP HiPCO individualisés, le rôle du polymère environnant sur les propriétés excitoniques des NTCMP LV, et les excitons sombres sont discutés dans cette thèse. Le design et la fabrication de guides optiques hybrides à une dimension, contenant une ou trois couches de NTCMP HiPCO, et de guides optiques à deux dimensions à base de NTCMP LV ont été menés. Les étapes de fabrication des guides optiques sont ici examinées en détails. La propagation à 1550nm de ces guides d’onde à base de NTCMP est observée. La propagation de la lumière dans les guides d’onde à base de NTCMP LV est une caractéristique préliminaire pour toute cavité optique et confère un fort potentiel aux NTCMP LV pour les composants photoniques de la future génération. / This thesis concentrates on the uniform deposition and highdensity alignment of single-walled carbon nanotubes (SWCNTs) on various substrates, the qualitative analysis of optical and excitonic properties, as well as vibrational modes of SWCNTbased samples by absorption, photoluminescence (PL) and Raman spectroscopies, and the fabrication of SWCNT-based optical waveguides towards photonics devices in the 1.55μm telecom window. Two types of SWCNT were studied during this thesis: “HiPCO” SWCNT from high pressure carbon monoxide conversion process (HiPCO) and “LV” SWCNT from catalytic growth of SWCNT assisted by laser vaporization (LV) of graphite. Several methods for the deposition of these SWCNTs were investigated and performed, including tube-assisted deposition method, groove deposition method, spraying method, high-speed spin coating method, improved low-speed spin coating method (ILSSCM) and inkjet printing method. The quality, thickness and uniformity of SWCNT films are characterized by scanning electron microscopy (SEM). The uniformity of HiPCO SWCNT-based film is shown to depend strongly on the surfactants concentration in deposited SWCNTbased dispersion. Uniform LV SWCNTbased films using ILSSCM were obtained with thicknesses ranging from 600nm to 900nm (with thickness error <10%), depending on substrates nature. Alignment of HiPCO and LV- SWCNTs using a dielectrophoresis method, combining microtechnological processes and SEM observations, is investigated and optimized. Thus, a new method (“heating-enhanced DEP”) for ultra-high alignment density of HiPCO SWCNTs is proposed. The effect of temperature in this heating-enhanced DEP process is further explained by simulation works. Optical and excitonic properties, vibrational modes of SWCNT solutions and films are characterized by absorption, PL and PL excitation, Raman spectroscopies. The defects and the isolation levels of HiPCO SWCNT, the chirality- and diameterdistributions of SWCNT, the uniformity and the thickness mapping of SWCNT-based films, and the effect of high energy laser are qualitatively analyzed by Raman spectra. We estimated the PL quantum efficiency value of HiPCO SWCNT film of around 5%. The exciton energy transfer between individualized HiPCO SWCNTs, the role of polymer environment on excitonic properties of LV SWCNTs, and the dark excitons are discussed in this thesis. One-layer and three-layers of HiPCO SWCNT-based onedimensional slab optical waveguides of hybrid core structures, and LV SWCNT-based twodimensional optical waveguides are designed and fabricated. The fabrication process steps of the optical waveguides are investigated in details. 1.55μm propagation in these SWCNT-based waveguides is highlighted. Single- or multi-mode emissions around 1.5μm and 1.6μm are observed in LV SWCNTbased optical waveguides. The light propagation in the LV SWCNT-based optical waveguide is the preliminary characteristic of an optical cavity, which confers great potential for future generation LV SWCNT-based photonics devices.

Optical biosensors are increasingly being considered for lab-on-a-chip applications due to their benefits such as small size, biocompatibility, passive behaviour and lack of the need for fluorescent labels. The light guiding mechanisms used by many of them result in poor overlap of the optical field with the target molecules, reducing the maximum sensitivity achievable. This thesis presents a new platform for optical biosensors, namely slotted photonic crystals, which engender higher sensitivities due to their ability to confine, spatially and temporally, the peak of optical mode within the analyte itself. Loss measurements showed values comparable to standard photonic crystals, confirming their ability to be used in real devices. A novel resonant coupler was designed, simulated, and experimentally tested, and was found to perform better than other solutions within the literature. Combining with cavities, microfluidics and biological functionalization allowed proof-of-principle demonstrations of protein binding to be carried out. High sensitivities were observed in smaller structures than most competing devices in the literature. Initial tests with cellular material for real applications was also performed, and shown to be of promise. In addition, groundwork to make an integrated device that includes the spectrometer function was also carried out showing that slotted photonic crystals themselves can be used for on-chip wavelength specific filtering and spectroscopy, whilst gas-free microvalves for automation were also developed. This body of work presents slotted photonic crystals as a realistic platform for complete on-chip biosensing; addressing key design, performance and application issues, whilst also opening up exciting new ideas for future study.

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)