Development of optical characterization methods for micro-and nano- scale planar photonic band gap structures

The characterization of photonic band gap materials (Photonic Crystals) is a fundamental issue in the development of the technologies for their fabrication and future application. This Doctoral Thesis has dealt with the development of optical characterization methods and their implementation to planar photonic structures. According to the objectives established in the present work we have obtained several results that are concluded in the following paragraphs: We have developed an experimental technique based on the Bragg diffraction in the near and middle infra red (IR) spectral range to determine the lattice properties of planar photonic structures. We have applied the Angular-Dependent Reflectance Spectroscopy technique (ADRS) to the characterization of photonic bands in PhC slabs. The objective was the implementation of the technique to our samples with lattice parameters that require the measurement to be carried out in the mid-IR spectral range. We have implemented the Angle-Resolved Spectroscopic Polarimetry to characterize the band structure of planar photonic-crystal structures in the visible spectral range. We have developed of a simulation tool and post-processing method to enhance the photonic bands recognition by the cited methods.La caracterización de materiales de gap fotónico (Cristales Fotónicos) es un aspecto fundamental en el desarrollo de las tecnologías para su fabricación y su futura utilización. Esta tesis doctoral se ha ocupado del desarrollo de métodos ópticos de caracterización, así como de su implementación en estructuras fotónicas planares, también conocidas como láminas de cristal fotónico (Photonic Cristal Slabs). De acuerdo con los objetivos fijados para el presente trabajo, hemos obtenido varios resultados, los cuales se resumen en los párrafos siguientes: Se ha desarrollado una técnica experimental basada en la difracción de Bragg en el rango espectral de la radiación infrarroja (IR) cercana y media, para determinar las propiedades de varias estructuras fotónicas planas. Se ha aplicado la técnica de la espectroscopia de reflectometría en ángulo variable (Angular-Dependent Reflectance Spectroscopy, ADRS) a la caracterización de bandas fotónicas en láminas de cristal fotónico. El objetivo ha sido la implementación de la técnica a las muestras fabricadas en el marco del grupo NePhoS de la Universitat Rovira i Virgili. Estas muestras tienen parámetros de red que requieren llevar a cabo una medición en un rango espectral del infrarojo (IR) medio. Finalmente, se ha desarrollado otra técnica óptica para caracterizar estructuras fotónicas planas: la polarimetría espectroscópica de ángulo variable

Remote Sensing of the Oceans

This book covers different topics in the framework of remote sensing of the oceans. Latest research advancements and brand-new studies are presented that address the exploitation of remote sensing instruments and simulation tools to improve the understanding of ocean processes and enable cutting-edge applications with the aim of preserving the ocean environment and supporting the blue economy. Hence, this book provides a reference framework for state-of-the-art remote sensing methods that deal with the generation of added-value products and the geophysical information retrieval in related fields, including: Oil spill detection and discrimination; Analysis of tropical cyclones and sea echoes; Shoreline and aquaculture area extraction; Monitoring coastal marine litter and moving vessels; Processing of SAR, HF radar and UAV measurements

Finite element methods for computational nonlinear optics

Unlike linear systems, where knowledge of the eigenvalues and eigenvectors allows one to write a closed-form solution, few nonlinear systems posses closed-form analytical solutions, and therefore numerical simulations play a crucial role in the process of finding and analysing nonlinear phenomena. For the theoretical study of the complex spatial, temporal and spatiotemporal behaviour of nonlinear optical systems, mathematical modelling of the problem under consideration by efficient stepping algorithms is necessary. For the past decade the Finite Element Method has proved to be a very efficient and versatile method in linear and nonlinear modal analysis with the use of variable meshes and infinite elements as some of its greatest strengths, but little work has been done on its application to evolutional analysis in nonlinear optics. This thesis describes a finite-element-based computer modelling of a wide range of nonlinear optical systems, with a view to developing an understanding of some of the complex but exciting spatial, temporal and spatiotemporal propagation dynamics in such systems. The computer simulation of a wide range of nonlinear optical waveguides and systems in those major areas of nonlinear optics which include nonlinear integrated-optics, nonlinear fiber-optics and nonlinear dynamic systems has been performed. This is carried out through numerical solutions of appropriate wave equations such as the paraxial wave equation, the Maxwell-Debye equations, the infinite-dimensional map of a ring resonator derived from the Maxwell-Bloch equations and coupled nonlinear Schroedinger equations that may include gain terms. Two well defined problems are addressed in detail. First, the determinations of the modes or characteristic solutions by solving the stationary wave equations through modal analysis of different types of nonlinear optical waveguides. Second, the determination of the paraxial propagation solutions along a nonlinear medium by solving the wave equation as step-by-step initial-boundary value problems through beam propagation analysis. For this task, current and novel 2D- and 3D- schemes based on the finite element method are presented and described. Particularly, a novel robust time-dependent code which is a combination of the finite-element propagation algorithm coupled to unconditionally stable difference schemes for marching the solutions along the characteristics of the (z,t)-domain is developed as well as accurate propagation schemes for solving generalized coupled nonlinear Schroedinger equations. Additionally, several novel specific applications involving nonlinear media are thoroughly described. These include the study of nonlinear supermodes of integrated-optics directional couplers, the nonlinear dispersion characteristics of multiple-quantum well waveguides and graded-index fibers with saturable nonlinear cores, controlled spatiotemporal soliton emission, switching and demultiplexing in nonlinear tapered waveguides, temporal optical soliton dynamics in active three-core nonlinear fiber directional couplers and two-dimensional solitary-wave optical memory in fibers and bistable ring cavities. The generation of ultrafast soliton-like pulsetrains from a c.w. dual-frequency input signal with sinusoidal modulation using a proposed novel dual-channel erbium-doped fiber coupler laser is also demonstrated

Reports of Planetary Geology and Geophysics Program, 1990

Abstracts of reports from NASA's Planetary Geology and Geophysics Program are presented. Research is documented in summary form of the work conducted. Each report reflects significant accomplishments within the area of the author's funded grant or contract