Imaging the first light: experimental challenges and future perspectives in the observation of the Cosmic Microwave Background Anisotropy

Measurements of the cosmic microwave background (CMB) allow high precision observation of the Last Scattering Surface at redshift $z\sim$1100. After the success of the NASA satellite COBE, that in 1992 provided the first detection of the CMB anisotropy, results from many ground-based and balloon-borne experiments have showed a remarkable consistency between different results and provided quantitative estimates of fundamental cosmological properties. During 2003 the team of the NASA WMAP satellite has released the first improved full-sky maps of the CMB since COBE, leading to a deeper insight into the origin and evolution of the Universe. The ESA satellite Planck, scheduled for launch in 2007, is designed to provide the ultimate measurement of the CMB temperature anisotropy over the full sky, with an accuracy that will be limited only by astrophysical foregrounds, and robust detection of polarisation anisotropy. In this paper we review the experimental challenges in high precision CMB experiments and discuss the future perspectives opened by second and third generation space missions like WMAP and Planck.Comment: To be published in "Recent Research Developments in Astronomy & Astrophysics Astrophysiscs" - Vol I

Polymer optical fiber gratings for microwave photonics and communications application

Tesis por compendio[ES] Con el continuo desarrollo de materiales y tecnologías de fabricación durante las últimas tres décadas, la atenuación de la transmisión de las fibras ópticas de polímero (POF) se ha reducido considerablemente. Las POF son ventajosas para las redes domésticas, así como para las interconexiones de almacenamiento, y tienen ventajas significativas para muchas aplicaciones de detección, que incluye el límite alto de tensión elástica, alta resistencia a la fractura, alta flexibilidad en la flexión, alta sensibilidad a la tensión y coeficientes termoópticos negativos. Esta tesis consigue mejorar la tecnología de irradiación con láser para POF e investiga dispositivos especiales basados en redes de difracción en POF para comunicaciones ópticas, microondas, fotónica y detección. En particular, desarrollamos la tecnología de fabricación rápida de FBGs en POF con un estudio detallado y la optimización de los parámetros de fabricación de redes de difracción de Bragg en fibra (FBG). Los resultados más destacados incluyen un FBG uniforme de 8 dB con un solo pulso láser Nd: YAG (26 nsm) (8 ns) basado en fibra dopada con BDK, que es el tiempo más corto presentado hasta ahora para la fabricación de FBGs en POF. La irradiación de fibras ópticas de polímero utilizando diferentes materiales basado en el láser KrF a 248 nm permitió demostrar un mejor rendimiento en comparación con el sistema que emplea el láser He-Cd a 325 nm. Además, se fabricaron FBGs uniformes en POFs de índice escalón dopadas con TS en menos de 1 segundo mediante la repetición de pulsos con baja energía. Finalmente, el estudio de la irradiación UV con pulsos de baja energía para la fabricación de redes de difracción estables permitió ahorrar energía en el proceso de fabricación de FBGs en POF, como uno de los principales requisitos para la producción en masa. Basándonos en la tecnología de fabricación mejorada, nos centramos en la fabricación de redes de difracción con diferentes estructuras: se fabricó un FBG con desplazamiento de fase utilizando dos pulsos de 15 ns a 248 nm KrF superpuestos por el método de Moiré; el primer FBG con chirp sintonizable se logró utilizando un solo pulso corto del láser, que abrió nuevas perspectivas a las aplicaciones basadas en redes de difracción con chirp en POF; también se propuso un nuevo método basado en gradientes térmicos para obtener FBG con chirp en POF basadas en FBG uniformes, y se demostró como la forma más conveniente publicada hasta la fecha para lograr este tipo de FBGs no uniformes en POF; y, finalmente, también se han fabricado redes de difracción de largo período utilizando un proceso de fabricación de corto tiempo, especialmente en comparación con investigaciones anteriores. En la última parte de la tesis, y en base a los dispositivos basados en redes de difracción obtenidos a lo largo de este trabajo, se han propuesto varias aplicaciones . De manera similar a los FBG en fibra de sílice, los FBGs con chirp en POF tienen muchas aplicaciones futuras en las áreas de comunicaciones ópticas y de los sensores. Este documento describe la aplicación de detección de tensión basada en una FBG con chirp sintonizable en POF, su aplicación para detección térmica en sistemas biomédicos; e ilustra el potencial de los dispositivos de dispersión sintonizables en el campo de las comunicaciones ópticas, bien como compensación de dispersión o en fotónica de microondas.[CA] Amb el continu desenvolupament de materials i tecnologies de fabricació durant les últimes tres dècades, l'atenuació de la transmissió de les fibres òptiques de polímer (POF) s'ha reduït considerablement. Els POF són avantatjosos per a les xarxes domèstiques, així com per a les interconnexions d'emmagatzematge, i tenen avantatges significatius per a moltes aplicacions de detecció, inclosos els límits de tensió elàstica alta, alta resistència a la fractura, alta flexibilitat en la flexió, alta sensibilitat a la tensió i potencials coeficients termoópticos negatius. Aquesta tesi va millorar la tecnologia d'irradiació amb làser per a POF i va investigar dispositius basats en xarxes difracció de Bragg (FBG) especials en POF per a comunicació òptica, microones, fotònica i detecció. En particular, desenvolupem la tecnologia de fabricació ràpida de FBG en POF amb un estudi detallat i l'optimització dels paràmetres per a la seua fabricació. Els punts destacats dels resultats inclouen un FBG uniforme de 8 dB amb un sol pols del làser Nd: YAG (266 nm) (8 ns) basat en fibra dopada amb BDK, que és el temps més curt reportat per a la fabricació de POF FBG. La irradiació de fibres òptiques de polímer utilitzant diferents materials sota el sistema de làser KrF a 248 nm va permetre demostrar un millor rendiment en comparació amb el sistema de làser Kimmon de 325 nm. A més, els FBG uniformes en el POF dopat amb TS d'índex escalonat es van aconseguir amb menys d'1 segon mitjançant la repetició de polsos de control i l'energia baixa de pols. Finalment, l'estudi de la irradiació d'energia de pols per a la fabricació de FBGs estables va permetre estalviar energia en el procés de fabricació de FBGs en POF, com un dels principals objectius de la producció en massa. Basant-nos en la tecnologia de fabricació millorada, ens centrem en la fabricació de diferents estructures de xarxes de difracció: es va fabricar un FBG amb desplaçament de fase utilitzant dos polsos de 15 ns a 248 nm KrF superposats pel mètode de Moiré; el primer FBG amb chirp sintonitzable es va aconseguir utilitzant un sol pols curt de làser, que va obrir les aplicacions basades en FBG amb chirp en POF; també es va proposar un nou mètode amb gradients tèrmics per a obtindre FBG en POF basat en FBG uniformes, i es va demostrar com la forma més convenient publicada fins hui per a aconseguir FBG POF estimulada; i, finalment, també s'han aconseguit xarxes de llarg període utilitzant un procés de fabricació de curt temps, especialment en comparació amb investigacions anteriors. Finalment, sobre la base dels dispositius de xarxes de difracció obtinguts al llarg d'aquest treball, s'han proposat diverses aplicacions potencials en aquesta tesi. De manera similar que per als FBG amb silici, el FBG amb chirp en POF té moltes aplicacions potencials en comunicacions òptiques i a l¿àrea de sensors. Aquest document descriu l'aplicació de detecció de tensió basada en FBG amb chirp sintonitzable en POF; a més, l'aplicació de detecció tèrmica en sistemes biomèdics; i el potencial dels dispositius de dispersió sintonitzables en les comunicacions òptiques, com per eixample a la compensació de dispersió o a la fotònica de microones.[EN] With the continuing development of material and fabrication technologies over the last three decades, the transmission attenuation of polymer optical fibers (POF) has been greatly decreased. POFs are advantageous for home networks as well as storage interconnections and have significant advantages for many sensing applications, including high elastic strain limits, high fracture toughness, high flexibility in bending, high sensitivity to strain and potential negative thermo-optic coefficients. This thesis improved the laser irradiation technology for POF and investigated special grating devices in POF for optical communication, microware photonics and sensing. In particular, we developed fast POF grating fabrication technology with a detailed study and optimization of the polymer optical fiber Bragg grating (POFBG) fabrication parameters. Highlights of the results include an 8 dB uniform POFBG with one single Nd:YAG (266nm) laser pulse (8 ns) based on BDK doped fiber, which is the shortest time ever reported for POFBG fabrication. The irradiation of polymer optical fibers using different materials under 248 nm KrF laser system allowed to demonstrate a better performance compared with 325 nm Kimmon laser system. Furthermore, uniform FBGs in step-index TS doped POF were achieved with less than 1 second by means of controlling pulse repetition and low pulse energy. Finally, the study of low UV pulse power irradiation for fabricating stable gratings allowed to save energy in the POF grating fabrication process, as one of the main goals for mass production. Based on the improved fabrication technology, we focused on the fabrication of different grating structures: a phase-shifted FBG was fabricated by using two 15 ns 248 nm KrF pulses overlapped by Moiré method; the first tunable chirped FBG was achieved by using a single laser short pulse, which opened the applications based on chirped POF BGs; also a novel thermal annealing method was proposed to obtain chirped POFBGs based on uniform FBGs, and proved as the ever published most convenient way to achieve chirped POFBG; and finally, long period gratings have been also achieved by using a short time fabrication process, specially when compared with previous research. Finally, based on the grating devices obtained throughout this work, several potential applications have been proposed in this thesis. Similarly, to silica chirped FBG, chirped FBG in POF have many potential applications in optical communications and sensing area. This document described the potential strain sensing application based on tunable chirped POFBG; also, the thermal detection application in bio-medical systems; and the potential of tunable dispersion devices in optical communications, i.e., dispersion compensation or microwave photonics.Min, R. (2019). Polymer optical fiber gratings for microwave photonics and communications application [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/125473TESISCompendi

Physics, Astrophysics and Cosmology with Gravitational Waves

Gravitational wave detectors are already operating at interesting sensitivity levels, and they have an upgrade path that should result in secure detections by 2014. We review the physics of gravitational waves, how they interact with detectors (bars and interferometers), and how these detectors operate. We study the most likely sources of gravitational waves and review the data analysis methods that are used to extract their signals from detector noise. Then we consider the consequences of gravitational wave detections and observations for physics, astrophysics, and cosmology.Comment: 137 pages, 16 figures, Published version <http://www.livingreviews.org/lrr-2009-2

Bit Bang 7: Future of Energy

This book is the 7th in the Bit Bang series of books produced as multidisciplinary teamwork exercises by doctoral students participating in the course Bit Bang 7: Future of Energy at Aalto University during the academic year 2014–2015. The course aims at fostering teamwork and multidisciplinary collaboration, as well as providing participants with a global, futurecentric perspective on the energy sector. The growing global demand for energy and diminishing natural resources are driving the development of eco-efficient energy sources, new ways of doing business, and designing our living environment. Bit Bang 7 addresses the topic of energy sources and technologies from the perspective of their economic, environmental and social sustainability. The course elaborates on the interconnectedness of these phenomena, and links them to possible future scenarios, global megatrends and ethical considerations. Will we see disruptive changes in our energy future? Can we impact consumption patterns, ways of doing business, and our way of life? Are we creating a sustainable future for the generations to come? Working in teams, the students set out to answer questions related to the changing energy sector and to brainstorm radical scenarios of what the future could hold. This joint publication contains articles produced as teamwork assignments for the course, in which the students were encouraged to take novel and radical views on the future of energy. The Bit Bang series of courses is supported by the Multidisciplinary Institute of Digitalisation and Energy (MIDE). Previous Bit Bang publications are available from http:/mide.aalto.fi

Affordances, constraints and information flows as ‘leverage points’ in design for sustainable behaviour

Copyright @ 2012 Social Science Electronic PublishingTwo of Donella Meadows' 'leverage points' for intervening in systems (1999) seem particularly pertinent to design for sustainable behaviour, in the sense that designers may have the scope to implement them in (re-)designing everyday products and services. The 'rules of the system' -- interpreted here to refer to affordances and constraints -- and the structure of information flows both offer a range of opportunities for design interventions to in fluence behaviour change, and in this paper, some of the implications and possibilities are discussed with reference to parallel concepts from within design, HCI and relevant areas of psychology

Report by the ESA-ESO Working Group on Fundamental Cosmology

ESO and ESA agreed to establish a number of Working Groups to explore possible synergies between these two major European astronomical institutions. This Working Group's mandate was to concentrate on fundamental questions in cosmology, and the scope for tackling these in Europe over the next ~15 years. One major resulting recommendation concerns the provision of new generations of imaging survey, where the image quality and near-IR sensitivity that can be attained only in space are naturally matched by ground-based imaging and spectroscopy to yield massive datasets with well-understood photometric redshifts (photo-z's). Such information is essential for a range of new cosmological tests using gravitational lensing, large-scale structure, clusters of galaxies, and supernovae. Great scope in future cosmology also exists for ELT studies of the intergalactic medium and space-based studies of the CMB and gravitational waves; here the synergy is less direct, but these areas will remain of the highest mutual interest to the agencies. All these recommended facilities will produce vast datasets of general applicability, which will have a tremendous impact on broad areas of astronomy.Comment: ESA-ESO Working Groups Report No. 3, 125 pages, 28 figures. A PDF version including the cover is available from http://www.stecf.org/coordination/esa_eso/cosmology/report_cover.pdf and a printed version (A5 booklet) is available in limited numbers from the Space Telescope-European Coordinating Facility (ST-ECF): [email protected]

Features and New Physical Scales in Primordial Observables: Theory and Observation

All cosmological observations to date are consistent with adiabatic, Gaussian and nearly scale invariant initial conditions. These findings provide strong evidence for a particular symmetry breaking pattern in the very early universe (with a close to vanishing order parameter, $\epsilon$), widely accepted as conforming to the predictions of the simplest realizations of the inflationary paradigm. However, given that our observations are only privy to perturbations, in inferring something about the background that gave rise to them, it should be clear that many different underlying constructions project onto the same set of cosmological observables. Features in the primordial correlation functions, if present, would offer a unique and discriminating window onto the parent theory in which the mechanism that generated the initial conditions is embedded. In certain contexts, simple linear response theory allows us to infer new characteristic scales from the presence of features that can break the aforementioned degeneracies among different background models, and in some cases can even offer a limited spectroscopy of the heavier degrees of freedom that couple to the inflaton. In this review, we offer a pedagogical survey of the diverse, theoretically well grounded mechanisms which can imprint features into primordial correlation functions in addition to reviewing the techniques one can employ to probe observations. These observations include cosmic microwave background anisotropies and spectral distortions as well as the matter two and three point functions as inferred from large-scale structure and potentially, 21 cm surveys.Comment: Invited review to IJMPD, 101 pages + 2 appendices, 29 figures, references added, matches journal versio

Non-Gaussianity in CMB analysis: bispectrum estimation and foreground subtraction

The focus of this work is the development of statistical and numerical methods forthe study of non-Gaussian and/or anisotropic features in cosmological surveys of themicrowave sky. We focus on two very different types of non-Gaussian (NG) signals. The former is primordial non-Gaussianity (PNG), generated in the very Early Universeduring the inflationary expansion stage. In this case the aim of our study will be that ofexploiting the NG component in order to extract useful cosmological information. The latter is non-Gaussianity generated by astrophysical foreground contamination. In thiscase, the goal is instead that of using non-Gaussianity as a tool to help in removingthese spurious, non-cosmological components (of course foregrounds themselves contain relevant astrophysical information, but the focus in this thesis is on Cosmology, thereforeforegrounds are regarded here only as a contaminant). Considerable efforts have been put so far in the search for deviations from Gaussianity in the CMB anisotropies, that are expected to provide invaluable information aboutthe Inflationary epoch. Inflation is in fact expected to produce an isotropic and nearly-Gaussian fluctuation field. However, a large amount of models also predicts very small,but highly model dependent NG signatures. This is the main reason behind the largeinterest in primordial NG studies. Of course, the pursuit for primordial non-Gaussianity must rely on beyond power spectrum statistics. It turns out that the most important higher order correlator produced by interactions during Inflation is the three pointfunction, or, more precisely, its Fourier space counterpart, called the bispectrum. Toovercome the issue of computing the full bispectrum of the observed field, that would require a prohibitive amount of computational time, the search for PNG features is carriedout by fitting theoretically motivated bispectrum templates to the data. Among those, one can find bispectrum templates with a scale-dependent (SD) bispectrum amplitude. Such templates have actually received little attention so far in the literature, especiallyas long as NG statistical estimation and data analysis are concerned. This is why a significant part of this thesis will be devoted to the development and application of efficientstatistical pipelines for CMB scale-dependent bispectra estimation. We present here theresults of the estimation of several primordial running bispectra obtained from WMAP9 year and Planck data-set. iiiThe second part of this thesis deals instead, as mentioned iin the beginning, withthe component separation problem, i.e. the identification of the different sources thatcontributes to the microwave sky brightness. Foreground emission produces several,potentially large, non-Gaussian signatures that can in principle be used to identify andremove the spurious components from the microwave sky maps. Our focus will be onthe development of a foreground cleaning technique relying on the hypothesis that, ifthe data are represented in a proper basis, the foreground signal is sparse. Sparsenessimplies that the majority of the signal is concentrated in few basis elements, that can be used to fit the corresponding component with a thresholding algorithm. We verifythat the spherical needlet frame has the right properties to disentangle the coherentforeground emission from the isotropic stochastic CMB signal. We will make clear inthe following how sparseness in needlet space is actually in several ways linked to thecoherence, anisotropy and non-Gaussianity of the foreground components.. The mainadvantages of our needlet thresholding technique are that it does not requires multi-frequency information as well as that it can be used in combination with other methods. Therefore it can represent a valuable tool in experiments with limited frequency coverage,as current ground-based CMB surveys