Studying dynamics of proteins in their biological milieu such as water is interesting because of their strong absorption in the terahertz range that contain information on their global and sub-global collective vibrational modes (conformational dynamics) and global dynamical correlations among solvent water molecules and proteins. In addition, water molecules dynamics within protein solvation layers play a major role in enzyme activity. However, due to the strong absorption of water in the gigahertz-to-terahertz frequencies, it is challenging to study the properties of the solvent dynamics as well as the conformational changes of protein in water. In response, we have developed a highly sensitive megahertz-to-terahertz dielectric spectroscopy system to probe the hydration shells as well as large-scale dynamics of these biomolecules. Thereby, we have deduced the conformation flexibility of proteins and compare the hydration dynamics around proteins to understand the effects of surface-mediated solvent dynamics, relationships among different measures of interfacial solvent dynamics, and protein-mediated solvent dynamics based on the complex dielectric response from 50 MHz up to 2 THz by using the system we developed. Comparing these assets of various proteins in different classes helps us shed light on the macromolecular dynamics in a biologically relevant water environment. / Doctor of Philosophy / Proteins are complicated biomolecules that exist in all living creatures and they are, mostly, involved in building up structures and cell functions in various biological systems. Not only their existence but also their complex movements and dynamics are vital to cell functions in living beings. Until recently, their chemical functions and dynamics have been extremely challenging to investigate and track in their native environments. Thanks to various efforts by researchers all over the world to learn more about their convoluted behavior, new techniques have arisen to study these properties. We, as a part of this community, have been able to develop highly sensitive megahertz-to-terahertz dielectric spectroscopy system to probe proteins and other biomolecules dynamics in picosecond to microsecond range. Using our benchmark system, we have been able to map the detailed dynamical properties of biomolecules as well as their exclusive hydration shell characterizations. In this work, we gathered details about three well-known proteins and biomolecules by studying their dielectric responses. Thus, we have been able to discuss the movements, relaxation processes and hydration shell properties of these molecules in liquid water as their basic native environment.

京都大学 / 新制・課程博士 / 博士(農学) / 甲第25348号 / 農博第2614号 / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 近藤 直, 准教授 小川 雄一, 教授 野口 良造 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

The optical frequency comb is a coherent light source whose spectrum consists of hundreds of thousands perfectly equidistant narrow frequency components and precisely expressed in just two radio frequencies. Even though optical frequency combs were developed 25 years ago, that led to the Nobel Prize in Physics 2005, only recently there was a significant progress in generating broadband optical frequency combs in the mid-infrared. These achievements became possible due to the development of new types of robust fiber and solid-state lasers and the efficient downconverting of their frequencies through different techniques based on advanced nonlinear crystals. In this dissertation, I study the techniques of producing ultra-broadband frequency combs in the challenging mid-infrared and terahertz regions of the electromagnetic spectrum. These combs find applications in high-precision molecular spectroscopy, atmosphere monitoring, reaction kinetics, and ultrasensitive trace gas detection to name a few. In addition, I investigate their application in the dual-comb spectroscopy, which is a tool involving two combs with slightly different comb line spacings that are interfered on a photodetector generating a radiofrequency comb. So, effectively high optical frequency is mapped to radiofrequency that can be easily recorded with available digital electronics. This method has a list of advantages over traditional spectrometers, namely broadband coverage combined with superior spectral resolution, high acquisition speed, high precision, and the absence of moving parts. Moreover, in the context of the experimental results, my spectroscopy investigations with low-pressure gases led to reliving a massive amount of spectroscopic data that had never been explored before, and some of which was already included into a global database. The results presented in this dissertation paves the way for creating highly accurate molecular spectroscopic databases and have the potential for real-time medical diagnostics through multi-species exhaled breath analysis.

Ce travail expérimental traite de la détection de radiations Térahertz (THz) par des transistors à base de silicium. Après avoir exposé le contexte de l'étude et les bases théoriques des modèles nécessaires à la compréhension du sujet, le manuscrit débute par une comparaison des transistors de haute mobilité électronique (HEMTs à base de matériaux III-V), aux transistors à base de silicium (Si-MOSFETs). Cette étude permet une meilleure compréhension du mécanisme physique responsable de la détection de radiations THz par les transistors à effet de champ de manière générale. La seconde partie de ce travail est consacrée à l'étude théorique et expérimentale de la longueur critique du canal Lc, liée à la distance d'amortissement des ondes de plasma et à partir de laquelle le signal de détection sature. Par ailleurs, le signal de détection THz de différents types de Si-MOSFETs a été étudié en fonction du champ magnétique, de la température et de la fréquence de l'onde THz incidente. Des raies inattendues et extrêmement marquées sont observées, jusqu'à la température ambiante, dans le signal de détection et dans la résistance du canal en champ magnétique. Celles-ci semblent être liées à une résonance de spin de facteur gyromagnétique égal à 2. L'allure générale du signal THz en champ magnétique est également discutée. Enfin, l'une des premières générations de détecteurs optimisés pour le THz et conçue dans le cadre d'un partenariat avec le CEA-LETI est présentée. Il s'agit notamment d'une matrice de pixels composés de Si-MOSFETs connectés à des antennes adaptées, à des amplificateurs de signaux, et à une première ébauche de circuit de lecture. La sensibilité, la puissance équivalent bruit (NEP) et la polarisation de ces détecteurs, est également étudiée en fonction de la fréquence incidente. Les résultats de cette étude mettent en exergue le potentiel de ces transistors nanométriques à base de Silicium entant que détecteur dans un système d'imagerie THz performant à température ambiante. / The experimental study reported here, deals with Therahertz (THz) radiation detection with silicon based transistors. After a brief overview of the context and the basics of the theory necessary to understand the subject, the report starts with a comparison betwen high mobility transistors (HEMTs based on III-V technolgies), and silicon transistors (Si-MOSFETs). This study allows a better understanding of the physical phenomenom responsible for THz radiation detection with field effect transistors in general. The second part is focalized on theoretical and experimental study of the critical chanel length (Lc), correlated to the distance of the plasma waves damping, from which the detection signal saturates. Beside, this THz detection signal, from diffrent kind of Si-MOSFETs, has been studied in magnetic field, in temperature, and in the frequency of the incomming radiation. Very pronounced and odd peaks are observed and studied, up to the ambiant temperature, inside the THz signal and the resistance of the MOS submited to magnetic field. These peaks seems to be linked by some way to a spin resonnance with a gyromagnetic factor of 2. The global tendancy of the evolution of the signal in magnetic field is also studied. Finally, one of the first generation of THz optimized detectors, develloped in partnership with CEA-LETI, is presented. Indeed, matrixes of pixels, composed of Si-MOSFETs connected to specific antennas, integrated amplifiers, and a basic reading circuit are studied. Sensitivity, noise equivalent power (NEP), polarization, of these detectors are caracterized. This study demonstrates the whole potential of these silicon based transistors as efficient THz imagery detectors for room temperature.

This thesis describes the experimental implementation of novel intersecting cavity terahertz optical parametric oscillators based on bulk and periodically-poled magnesium oxide-doped lithium niobate. Both collinear and non-collinear phase-matching geometries have been demonstrated and injection-seeding has been implemented in devices using periodically-poled material to reduce threshold and increase the down-conversion efficiency. A comprehensive characterisation of the original intracavity terahertz OPO was undertaken, which revealed the parameters having the greatest impact on OPO efficiency (idler mirror reflectivity and cavity length) and led to a better understanding of the losses in the system. During the characterisation process, generation of further terahertz radiation at the same frequency as that generated by the parametric process was observed and identified as being a result of difference frequency generation (DFG) between the parametrically-generated idler and terahertz waves. This phenomenon had previously only been observed when periodically-poled materials were employed in the system. The effect of this additional DFG process has been analysed in terms of the enhancement of the terahertz field on the basis of the coupled wave equations and physically measured quantities. The use of periodically-poled lithium niobate has been a major part of the research presented in this thesis. A comprehensive study of the modified phase-matching conditions was carried out and both collinear and novel hybrid non-collinear phase-matching geometries were identified. Several computer models were developed to assess the performance of any given grating design in these different geometries and the effects of temperature tuning and pump wavelength variation were also investigated using the models. Experimental studies confirmed the viability of the modelling approach but material limitations (particularly the early onset of crystal damage) limited the outcomes of the experiments. A detailed comparison of the poled and bulk materials was made to highlight the present drawbacks of the poled material. Finally, injection seeding was used to improve the efficiency of the collinear phase-matched PPLN OPOs. When seeding was used the depletion of the pump pulse was increased to the point of being measurable, reaching an upper level of 10%. Coupling constraints placed on the seed laser limited the amount of depletion attained. The potential for injection seeding to be used in the hybrid non-collinear phase-matching scheme was also identified but not realised during the course of this work. Were this technique successful, the tuning range of the intersecting cavity terahertz OPO could be extended to encompass the sub-1THz region, something that has previously been limited by the available idler cavity angles.

Esta tese de doutorado trata do desenvolvimento de circuitos para a deteção de ondas submilimétricas integrados em tecnologia CMOS. Existe um interesse crescente nas tecnologias que utilizam frequências em terahertz (300 GHz - 3 THz) para aplicações em diagnóstico médico por imagem, análise espectral, segurança, radiocomunicação, aplicações médicas e de inspeção. Os sistemas atuais que utilizam tecnologias fotônicas são complexos e consomem muito espaço, além de pouco acessíveis devido ao seu alto custo. Porém, com o advento das tecnologias de silício (eg. CMOS e BiCMOS) é possível desenvolver circuitos nesta faixa de frequência, com baixo custo e alta capacidade de integração, permitindo inclusive o processamento do sinal no próprio chip. Diante deste contexto, as investigações desta tese de doutorado pretendem analisar e contribuir com o desenvolvimento de circuitos de detecção de ondas sub-milimétricas, bem como, propor uma metodologia de projeto que permita a integração destes circuitos e suas antenas em tecnologia CMOS, e com especificações para aplicação em um sistema de identificação por imagem. Este sistema é composto por antena, interface para detecção e processamento do sinal. Alguns detectores com antenas patch acopladas e com variações topológicas foram fabricados em tecnologia CMOS de 180 nanometros e testados para diferentes faixas de frequências, que vão desde 400 GHz até 800 GHz. Também foi desenvolvido um arranjo de detectores com 12 pixels (4x3) para a faixa de 700 GHz a 770 GHz, para aplicação em sistemas de identificação por imagem. A análise, o projeto e os testes destes circuitos, bem como a sua aplicação e a comparação dos mesmos com os apresentados em outros trabalhos, são discutidos ao longo desta tese. Os circuitos foram testados com um setup proposto adaptando-se um sistema de espectroscopia no domínio do tempo, comprovando os resultados através de testes experimentais. / This PhD thesis deal with the development of circuits for submillimeter waves detection integrated in CMOS technology. There is a growing interest in technologies that uses terahertz frequencies (300 GHz to 3 THz) for applications in medical imaging, spectral analysis, security, radiocommunication, medical applications and inspection. The present systems that uses photonic technology are complex and space consuming, and also are very expensives. However, with the advent of silicon technologies (eg. CMOS and BiCMOS) is possible to develop circuits to work in this frequency range, with low cost and high integrability, including the on-chip signal processing. Given this context the investigations of this PhD thesis intends to analyze and to contribute with the development of submillimeter waves detection circuits as well as to propose a design metodology that allows the circuit integration and its antennas in CMOS technology and with specifications for application in imaging system. This system is composed by antenna, detection interface and signal processing. Some detectors with coupled patch antenna and with topological variations were fabricated in 180 nanometers CMOS technology and tested for different frequency ranges, that ranging from 400 GHz until 800 GHz. Also was developed a detector array with 12 pixels (4x3) for the 700 to 770 GHz frequency range (120 GHz bandwidth), for application in imaging systems. The analysis, design and testing of these circuits as well as their application and their comparison with those presented in other works, are discussed throughout this thesis. The circuits were tested using a proposed setup using a terahertz time-domain spectroscopy system confirming the results through experimental tests.

Le domaine des ondes TeraHertz (THz) s’étend de l’infrarouge lointain (15 μm / 20 THz) aux ondes radios (3000 μm / 0.1 THz). La couverture spectrale des sources actuelles, qu’elles soient thermique (lampes à mercure…), électronique (diode Gunn…) ou optique (laser, antennes…), ne permet pas de répondre à l’ensemble des applications en spectroscopie et en imagerie. Une alternative à ces sources est l’optique non linéaire paramétrique, qui permet de générer des ondes THz à partir du processus de Différence de Fréquences (DFG), et qui consiste à injecter un ou deux lasers dans un cristal non linéaire. Afin de couvrir au mieux le très large domaine THz, il est nécessaire de déterminer un ensemble de cristaux dont les propriétés optiques permettent de générer ces ondes avec de forts rendements de conversion.Le travail présenté dans ce manuscrit de thèse décrit l’étude de ces propriétés pour un ensemble de cristaux non linéaires, ainsi que des résultats expérimentaux de génération THz à partir de la DFG entre deux lasers monochromatiques en régime nanoseconde et picoseconde, ou entre deux composantes de Fourier au sein d’une impulsion laser femtoseconde. Nous avons sélectionné vingt nouveaux cristaux jamais étudiés dans le domaine THz auparavant, ainsi que le nouveau cristal organique de BNA. Nous avons mesuré leurs spectres de transmission du visible au THz, ainsi que les propriétés optiques non linéaires incluant les conditions d’accord de phase et le rendement de conversion. / THz-waves extend from the far InfraRed (15 μm – 20 THz) to radio waves (3000 μm – 0.1 THz). Current sources based on thermal (Mercury lamps…), electronics (Gunn diode...) or optics (laser, antennas…) technologies can’t cover this wide spectral range for applications in spectroscopy and imaging. An alternative is provided by parametric nonlinear optics, which leads to the generation of THz waves from Difference Frequency Generation (DFG) by injecting one or two lasers in a nonlinear crystal. To better cover the wide THz domain, it is necessary to determine nonlinear crystals with optical properties leading to the generation of such waves with high conversion efficiencies.This PhD thesis is devoted to the study of these properties for a panel of nonlinear crystals, along with experimental results of THz generation from DFG between two monochromatic lasers in the nanosecond and picosecond regimes, or between two Fourier components within a femtosecond laser. We selected twenty new crystals never studied before in the THz domain, along with the organic crystal of BNA. We measured their transmission spectra from visible to THz, and their nonlinear properties including phase-matching conditions and conversion efficiency.

Esta tese de doutorado trata do desenvolvimento de circuitos para a deteção de ondas submilimétricas integrados em tecnologia CMOS. Existe um interesse crescente nas tecnologias que utilizam frequências em terahertz (300 GHz - 3 THz) para aplicações em diagnóstico médico por imagem, análise espectral, segurança, radiocomunicação, aplicações médicas e de inspeção. Os sistemas atuais que utilizam tecnologias fotônicas são complexos e consomem muito espaço, além de pouco acessíveis devido ao seu alto custo. Porém, com o advento das tecnologias de silício (eg. CMOS e BiCMOS) é possível desenvolver circuitos nesta faixa de frequência, com baixo custo e alta capacidade de integração, permitindo inclusive o processamento do sinal no próprio chip. Diante deste contexto, as investigações desta tese de doutorado pretendem analisar e contribuir com o desenvolvimento de circuitos de detecção de ondas sub-milimétricas, bem como, propor uma metodologia de projeto que permita a integração destes circuitos e suas antenas em tecnologia CMOS, e com especificações para aplicação em um sistema de identificação por imagem. Este sistema é composto por antena, interface para detecção e processamento do sinal. Alguns detectores com antenas patch acopladas e com variações topológicas foram fabricados em tecnologia CMOS de 180 nanometros e testados para diferentes faixas de frequências, que vão desde 400 GHz até 800 GHz. Também foi desenvolvido um arranjo de detectores com 12 pixels (4x3) para a faixa de 700 GHz a 770 GHz, para aplicação em sistemas de identificação por imagem. A análise, o projeto e os testes destes circuitos, bem como a sua aplicação e a comparação dos mesmos com os apresentados em outros trabalhos, são discutidos ao longo desta tese. Os circuitos foram testados com um setup proposto adaptando-se um sistema de espectroscopia no domínio do tempo, comprovando os resultados através de testes experimentais. / This PhD thesis deal with the development of circuits for submillimeter waves detection integrated in CMOS technology. There is a growing interest in technologies that uses terahertz frequencies (300 GHz to 3 THz) for applications in medical imaging, spectral analysis, security, radiocommunication, medical applications and inspection. The present systems that uses photonic technology are complex and space consuming, and also are very expensives. However, with the advent of silicon technologies (eg. CMOS and BiCMOS) is possible to develop circuits to work in this frequency range, with low cost and high integrability, including the on-chip signal processing. Given this context the investigations of this PhD thesis intends to analyze and to contribute with the development of submillimeter waves detection circuits as well as to propose a design metodology that allows the circuit integration and its antennas in CMOS technology and with specifications for application in imaging system. This system is composed by antenna, detection interface and signal processing. Some detectors with coupled patch antenna and with topological variations were fabricated in 180 nanometers CMOS technology and tested for different frequency ranges, that ranging from 400 GHz until 800 GHz. Also was developed a detector array with 12 pixels (4x3) for the 700 to 770 GHz frequency range (120 GHz bandwidth), for application in imaging systems. The analysis, design and testing of these circuits as well as their application and their comparison with those presented in other works, are discussed throughout this thesis. The circuits were tested using a proposed setup using a terahertz time-domain spectroscopy system confirming the results through experimental tests.

Au cours des dernières années, la communauté scientifique s'est intéressée de plus en plus à l'acquisition de sources d'énergie renouvelables vertes et propres par rapport aux combustibles fossiles traditionnels. Le rayonnement solaire est une source particulièrement abondante d'énergie renouvelable qui a été largement utilisée dans les véhicules, les machines et les bâtiments, entre autres. Il y a généralement deux manières différentes d'utiliser l'énergie solaire: la chaleur et l'électricité. La principale motivation de ce travail de thèse est d'utiliser cette abondante source d'énergie pour produire une petite fraction de la tension et du courant continu de sortie. Puisque le spectre solaire se situe dans les longueurs d'onde à l'échelle nanométrique ou dans la bande térahertz, les antennes optiques seront utilisées comme une nouvelle technologie de nanotechnologie pour capter et récolter l'énergie solaire. Les antennes optiques ont des propriétés similaires à celles de leurs homologues micro-ondes, mais leur avantage réside dans des moyens sans précédent pour adapter les champs électromagnétiques dans tous leurs aspects et applications. Par conséquent, avec les détails mentionnés ci-dessus, l'idée principale de cette thèse est de capturer le rayonnement infrarouge solaire et l'utiliser pour produire une tension continue de sortie. La première partie de cette thèse est consacrée à la compréhension du fonctionnement de la collecte d'énergie par radiofréquence (RF) et à la présentation d'un concept de rectenna. La deuxième partie traite de l'introduction et de la simulation d'antennes optiques à base de résonateurs diélectriques (DR) car elles offrent moins de pertes à la bande THz. Deux conceptions de DR différentes sont proposées fonctionnant à la fréquence centrale de 193,5 THz (longueur d'onde 1550 nm). La troisième partie traite de la contribution principale à ce travail en termes de conception, simulation et fabrication d'une antenne optique Yagi-uda à haut gain et large bande. La technique de lithographie par faisceau d'électrons est utilisée pour réaliser la structure proposée. En dehors de la conception de l'élément unique Yagi-uda, diverses configurations de réseau ont été simulées avec la réalisation d'un réseau d'éléments 100 x 100 fabriqué sur un substrat de silicium. Pour produire une certaine quantité de tension de sortie, deux techniques ont été utilisées pour tester le réseau d'antennes optiques Yagi-uda. La première technique impliquait l'intégration du réseau Yagi-uda avec une diode fermionique du commerce qui produisait une tension de sortie de 0,15 V par excitation à partir d'une lumière visible et de 0,52 V par excitation directe à partir d'un laser à 1550 nm. La deuxième technique est basée sur la dissipation thermique entre des métaux dissemblables produisant une tension de sortie. Quatre lasers à longueurs d'onde différents (532 nm, 650 nm, 940 nm et 1550 nm) ont excité trois conceptions de nantenna réalisées. Parmi ces conceptions, la tension de sortie maximale de 0,82 V a été produite par le réseau Yagi-uda lorsqu'il est excité via un laser de 1550 nm. / Recent years have witnessed an increased interest by the scientific community to acquire green and clean renewable sources of energy compared to traditional fossil fuels. Solar radiation is one particular abundant source of renewable energy that has been widely applied in vehicles, machines, and buildings, among others. There are generally two different ways in which solar energy is used – heat and electricity. The main motivation of this thesis work is to utilize that abundant source of energy in producing a small fraction of output DC voltage and current. Since the solar spectrum lies in the nano scale wavelengths or terahertz band, optical antennas as a novel nano fabrication technology will be used to capture and harvest the solar energy. Optical antennas have properties similar to their microwave counterparts, but the advantage they have is in terms of unprecedented means to tailor electromagnetic fields in all its aspects and applications. Therefore, with the aforementioned details, the main idea of this thesis is to capture the solar infrared radiation and utilize it for producing output DC voltage. The first part of this thesis is dedicated to understanding the working of radio frequency (RF) energy harvesting and presenting a rectenna design. The second part deals with the introduction and simulation of optical antennas based of dielectric resonators (DR) as they offer fewer losses at the THz band. Two different DR designs are proposed working at the center frequency of 193.5 THz (1550 nm wavelength). The third part discusses the main contribution to this work in terms of design, simulation and fabrication of a high gain and wideband Yagi-uda optical antenna. E-beam lithography technique is used to realize the proposed structure. Apart for the single element Yagi-uda design, various array configurations have been simulated with realization of a 100 x 100 elements array fabricated on a silicon substrate. To produce a certain amount of output voltage, two techniques were deployed in testing the realized Yagi-uda optical antenna array. The first technique involved integration of the Yagi-uda array with a commercial fermionic diode that produced output voltage of 0.15 V via excitation from a visible light and 0.52 V with direct excitation from a 1550 nm laser. The second technique is based on thermal dissipation among dissimilar metals producing an output voltage. Four different wavelength (532 nm, 650 nm, 940 nm and 1550 nm) lasers excited three realized nantenna designs. Among these designs, the maximum output voltage of 0.82 V was produced by the Yagi-uda array when excited via 1550 nm laser.

Terahertz radiation or T-rays or THz radiation refers to the region of the electromagnetic spectrum between approximately 100 GHz and 30 THz. This spectral region is often referred to as the THz gap as these frequencies fall between electronic (measurement of field with antennas) and optical (measurement of power with optical detectors) means of generation. THz measurements may yield useful information about the structural and chemical nature of the material inspected. Examples include detection of voids in materials and protein binding in biomolecules. This report provides an overview of THz measurements of defects in fiber composites. We find that it efficiently detects defects such as voids and delamination in glass fiber composites better than ultrasound, which was widely used for defect characterization in glass fiber earlier. Comparison of the existing methods with THz is presented in the report for characterization of defects.