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Design, Modeling, and Characterization of Innovative Terahertz Detectors Duy Thong Nguyen

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Design, Modeling, and Characterization of Innovative Terahertz Detectors Duy Thong Nguyen Design, modeling, and characterization of innovative terahertz detectors Duy Thong Nguyen To cite this version: Duy Thong Nguyen. Design, modeling, and characterization of innovative terahertz detectors. Elec- tromagnetism. Université de Grenoble, 2012. English. tel-00773019 HAL Id: tel-00773019 https://tel.archives-ouvertes.fr/tel-00773019 Submitted on 15 Jan 2013 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. THÈSE Pour obtenir le grade de DOCTEUR DE L’UNIVERSITÉ DE GRENOBLE Spécialité : Optique et Radiofréquences Arrêté ministériel : 7 août 2006 Présentée par Duy Thong NGUYEN Thèse dirigée par Jean-Louis COUTAZ et codirigée par François SIMOENS préparée au sein du Laboratoire CEA-Léti dans l'École Doctorale EEATS Conception, modélisation et caractérisation de détecteurs térahertz innovants Thèse soutenue publiquement le 12 novembre 2012 devant le jury composé de : Pr. Jean-Louis COUTAZ Professeur, IMEP-LAHC, Université de Savoie, directeur de thèse Dr. Gian Piero GALLERANO Chef du Laboratoire des Sources de Rayonnement, ENEA, Frascati (Italie), rapporteur Pr. Ronan SAULEAU Professeur, IETR, Université de Rennes, rapporteur Dr. François SIMOENS Responsable du programme stratégique "Imageurs", CEA-LETI Grenoble, encadrant de thèse Pr. Carlo SIRTORI Professeur, LMPQ, Université de Paris 7 Diderot, Président UNIVERSITY OF GRENOBLE Number attributed by library __________ PhD Thesis in partial fulfillment to obtain the degree of DOCTEUR OF PHYSICS Doctoral Course : Optics & Radiofrequencies Doctoral School : EEATS (Electronique, Electrotechnique, automatique, Télécommunications, Signal) Design, modeling, and characterization of innovative terahertz detectors Prepared by NGUYEN Duy Thong under the direction of Pr. Jean-Louis COUTAZ at CEA, Leti, Department of Optoelectronics, MINATEC Campus To be defended on 12 November, 2012 in front of the following examining committee JURY Gian Piero GALLERANO PhD, ENA, Italy Referee Ronan SAULEAU Professor, IETR , France Referee Carlo SIRTORI Professor, University of Paris 7, France Examiner François SIMOENS PhD, CEA-Leti, France Supervisor Jean-Louis COUTAZ Professor, University of Grenoble PhD Supervisor Abstract Design, modeling, and characterization of innovative terahertz detectors This PhD thesis aims to establish an electromagnetic modeling of the bolometer at terahertz (THz) range that can facilitate the design of the detector from the uncooled infrared bolometer technology. The envisaged application for the detectors lies in active THz imaging at room temperature. We have studied the optical coupling of a THz antenna-coupled bolometer operating in the range 1 – 5 THz. Simulations in receiving and transmitting modes have been performed to study the optical characteristics of the bolometer. The combination of these two simulation types leads to a powerful toolset to design terahertz bolometers. For the experimental aspect, measurements have been performed by using Fourier-transform technique to study experimentally the electromagnetic behavior of the bolometer. They are measurement of reflectivity of the focal plane array’s surface and spectral response measurement. The results of measurement were found to be in good agreement with the simulation. The understanding from the study in this PhD helps us make improvement to the actual detector. Also the design of bolometer for low frequency (850 GHz) has been proposed. This leads to a perspective of using bolometer for terahertz imaging at the frequency where many characteristic of the terahertz radiation are favorable for imaging application. Key words: Terahertz, antenna-coupled bolometer, electromagnetic simulation, Fourier- transform spectroscopy, spectral response, terahertz imaging. Résumé Conception, modélisation et caractérisation de détecteurs térahertz innovants Le but de cette thèse est d’établir une modélisation électromagnétique du détecteur bolométrique térahertz (THz). Ce travail aide à faciliter la conception de bolomètre THz dont la structure est basée sur celle de bolomètre infrarouge à température ambiante. Le contexte de la thèse est l’imagerie THz active. Nous avons étudié le comportement électromagnétique d’un bolomètre à antenne de bande spectrale 1 – 5 THz. Deux modes de simulation ont été réalisées μ l’une est en mode de réception et l’autre est d’émission. La combinaison de ces modes de simulation constitue un outil important pour concevoir le bolomètre THz. La technique de spectroscopie par transformée de Fourier a été utilisée pour caractériser expérimentalement le comportement électromagnétique du détecteur. Nous avons mesuré la réflectivité de la surface du plan focal de détecteur ainsi que la réponse spectrale du détecteur. Les deux sont confrontées avec la simulation et elles se trouvent en bon accord. Avec les connaissances obtenues des résultats théorique et mesuré, la recherche aide à améliorer des performances du détecteur actuel. Nous avons aussi proposé un design pour le bolomètre de faible fréquence (850 GHz). Ce dernier ouvre la perspective d’emmener la technologie de bolomètre d’infrarouge vers la bande sous-térahertz où l’imagerie est beaucoup plus favorable. Mots clés : Térahertz, bolomètre à antenne, simulation électromagnétique, spectroscopie par transformée de Fourier, réponse spectrale, imagerie térahertz NGUYEN Duy Thong i TABLE OF CONTENTS Abstract ................................................................................................................................................................... i Acknowledgements ............................................................................................................................................... iv Chapter 1 Introduction to THz science & technologies ............................................................................... 1 1.1 Terahertz domain ...................................................................................................................................... 1 1.1.1 Technological development of THz components and systems ......................................................... 1 1.1.2 Features of THz domain .................................................................................................................. 2 1.1.3 Applications of THz waves .............................................................................................................. 5 1.2 Imaging in the THz domain ...................................................................................................................... 7 1.2.1 Common specifications of imaging systems .................................................................................... 7 1.2.2 Other important features of terahertz imaging.............................................................................. 10 1.2.3 Passive imaging vs active imaging ................................................................................................ 13 1.2.4 Context of the PhD work: THz imaging with room-temperature bolometer array ....................... 17 1.3 Summary ................................................................................................................................................. 19 References ........................................................................................................................................................ 20 Chapter 2 Bolometric detectors ................................................................................................................... 23 2.1 Principle of bolometer ............................................................................................................................ 23 2.1.1 Bolometer overview ....................................................................................................................... 23 2.1.2 Electro-thermal model ................................................................................................................... 25 2.1.3 Noise in bolometers ....................................................................................................................... 29 2.1.4 Figures of merit ............................................................................................................................. 32 2.2 Summary ................................................................................................................................................. 34 References ........................................................................................................................................................ 35 Chapter 3 IR-THz transformation for uncooled bolometer ...................................................................... 36 3.1 Cryogenic terahertz bolometer ................................................................................................................ 36 3.1.1 Antenna-coupled bolometer .......................................................................................................... 36 3.1.2 Distributed absorbing element bolometer
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