Дисертації з теми "Terahertz electronics"
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Lucyszyn, Stepan. "Millimetre-wave and terahertz electronics." Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/6974.
Othman, Mohd Azlishah. "Sub-Terahertz : generation and detection." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13375/.
Shen, Hao. "Compressed sensing on terahertz imaging." Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/8457/.
Glynn, David William. "Terahertz frequency doubling circuits for communications." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7517/.
Salmans, Parker Dean. "Semiconductor Terahertz Electronics and Novel High-Speed Single-Shot Measurements." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6544.
Escorcia, Carranza Ivonne. "Metamaterial based CMOS terahertz focal plane array." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6955/.
Khiabani, Neda. "Modelling, design and characterisation of terahertz photoconductive antennas." Thesis, University of Liverpool, 2013. http://livrepository.liverpool.ac.uk/14213/.
Ledwosinska, Elzbieta. "Graphene as a mechanical or electrical transducer for far-infrared / terahertz detection." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119378.
Nous tentons de remplir "le trou THz" pour les détecteurs hautes performance en utilisant les propriétés mécaniques du graphène dans une cellule miniature de Golay ainsi que les propriétés électriques du graphène hydrogéné dans un microbolomètre. La cellule de Golay est le détecteur le plus sensible de THz à température pièce sur le marché, mais requiert une miniaturisation comme première étape d'intégration à une grille d'imagerie. En ce moment, des membranes ultra minces pour des cellules de Golay miniatures souffrent de responsivité diminuée lorsque les dimensions latérales sont réduites. Nous proposons le graphène comme candidat idéal pour la membrane, car sa dureté élastique minimale grâce à sa nature monoatomique permet un agrandissement jusqu'à l'échelle microscopique. Nous simulons la déflection de la membrane en fonction de la température et analysons la géométrie de cellule optimale avec une sensibilité prédite de tripler par rapport à la technologie actuelle qui est quatre fois plus grande. Afin de fabriquer cette cellule, nous avons développé la première méthode de transfert de graphène suspendu sans organiques sur une échelle de 10 − 20 μm. La microscopie Raman, Auger, à balayage électronique et à transmission électronique (TEM) confirment du graphène de haute qualité sans aucune contamination à part celle de l'air ambiant. Cette méthode s'applique non seulement pour construire la cellule, mais aussi pour des études fondamentales du graphène ou la propreté est d'une importance capitale. Par ailleurs, nos méthodes culminent dans une application commerciale soit celle d'une grille TEM à base de graphène. Nous présentons une analyse théorique de lecture optique interférométrique. Nous implémentons ensuite de la microscopie par force atomique afin de caractériser mécaniquement et rapporter la déflection à température pièce (jusqu'à 60◦C) de notre cellule, démontrant ainsi la validation du concept. Finalement, nous examinons et utilisons les propritétés thermiques du graphène hydrogéné afin de produire un microbolomètre avec une responsivité de R ≈ 10^5 V/W, ce qui est comparable avec des bolomètres commerciaux à base de Si.
Barnes, Mark. "Terahertz emission from ultrafast lateral diffusion currents within semiconductor devices." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/363127/.
Smith, Shane Raymond. "Construction and characterization of a multi-antenna terahertz time-domain spectroscopy setup." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96733.
ENGLISH ABSTRACT: Recent progress in laser and semiconductor technology has allowed for far easier generation and measuring of coherent terahertz radiation, a previously difficult region in the radiation spectrum to coherently generate. Time based terahertz spectroscopy is a rather unique form of spectroscopy. Not only is it time based, but the electric field is measured instead of the intensity. This allows for the measurement of the complex refractive index. From this one can obtain certain details of the structure and environment of the sample being studied. A terahertz time-domain spectroscopy setup was constructed during this project. This setup used low temperature grown GaAs photoconductive antennae, with multiple antenna size options available for both the receiving and transmitting antennae. After the construction and alignment of this setup, the antennae were characterized. Lastly measurements were performed on the background, sugar and silicon to demonstrate the capabilities of the system. It was found that the measured terahertz electric field amplitude increased with the intensity of the pump pulse and that the amplitude of the measured terahertz electric field was dependent on the polarization of the pump pulse. As the size of the antenna was increased so too did the amplitude of the measured electric field and conversely the bandwidth of the measured terahertz electric field decreased with the increase of antenna size. This held true for both the transmitting and receiving antennae.
AFRIKAANSE OPSOMMING: Danksê onlangse tegnologiese onwikkelings in lasers en halfgeleier het dit veel makliker geraak om terahertz straling te genereer wat fase samehangendheid toon. Voor hierdie ontwikkelings was straling in hierdie spektrale gebied moeilik om te genereer op ’n wyse wat fase samehangendheid toon. Tyd verwante terahertz spektroskopie is taamlik uniek, aangesien die metings in tyd geneem word en die elektriese veld amplitude word pleks van die intensiteit gemeet. Een van die voordele van hierdie metode is dat dit toelaat vir die meeting van die komplekse brekingsindeks van monsters. Dit is moontlik om van die komplekse brekingsindeks strukturele en omgewings eienskappe van die monster af te lei. Gedurende die projek was ’n tyd verwante terahertz spektroskopie sisteem gebou wat gebaseer was op lae temperatuur gegroeide GaAs foto-geleidende antennas. Die sisteem bevat vier antennas van verskillende groottes aan beide die sender en ontvanger kant. Die antennas was gekarakteriseer na die bou en belyning van die terahertz sisteem en meetings was gedoen op die agtergrond, suiker en silikon om die sisteem se vermoë te demonstreer. Dit was gevind dat die amplitude van die gemete terahertz elektriese veld groter geraak het soos die intensiteit van die pomp puls verhoog was en dat die die amplitude van die gemete terahertz electriese veld afhanklik was van die polarisasie van die pomp puls. Die amplitude van van die gemete terahertz elektriese veld het gegroei met die grootte van die antenna, maar hoe groter die antenna geraak het, hoe kleiner was die bandwydte van die gemete terahertz elektriese veld. Hierdie was die geval vir beide die sender en ontvanger antennas.
Yanson, Dan Andreyevitch. "Generation of terahertz-modulated optical signals using AlGaAs/GaAs laser diodes." Thesis, University of Glasgow, 2004. http://theses.gla.ac.uk/2837/.
Kotiranta, Mikko [Verfasser], Viktor [Akademischer Betreuer] Krozer, and Claudio [Akademischer Betreuer] Paoloni. "Development of terahertz vacuum electronics for array receivers / Mikko Kotiranta. Gutachter: Viktor Krozer ; Claudio Paoloni." Frankfurt am Main : Univ.-Bibliothek Frankfurt am Main, 2013. http://d-nb.info/1044413441/34.
Shang, Xiaobang. "SU-8 micromachined terahertz waveguide circuits and coupling matrix design of multiple passband filters." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/3087/.
Geffroy, Clément. "Impulsions ultra-courte d'électron unique pour les qubits volants." Electronic Thesis or Diss., Université Grenoble Alpes, 2023. http://www.theses.fr/2023GRALY101.
The second quantum revolution of the 20th century contributed to a technological expansion in solid-state physics. Modern nanofabrication coupled to material processing techniques have facilitated the development of on-demand single-electron sources. With their remarkable precision, they are currently used for metrology purposes and hold key potential for the recent field of research of electron quantum optics, including a promising candidate for quantum information: the electron flying qubit. These quantum bits are created by short voltage pulses and manipulation of their quantum state occurs on-the-fly. The shortest voltage pulse reported so far attains 27 ps, on-chip, in a cryogenic environment. However, suffering from attenuation and dispersion in coaxial lines, accessibility to electronic quantum regimes at faster time scale remains out-of-reach.On the contrary, empowered by the advent of ultrafast lasers and progress in photonics and plasmonics, photo-conductive-switch technology can allow the generation of electromagnetic pulses with picosecond duration. The large bandwidth of these THz opto-electronic technologies could overcome the technical bottleneck faced by standard electronic equipment. While they have been widely developed for room temperature applications, demonstrations of their integration along-side a quantum architecture in a cryogenic environment are still limited. The realisation of such an experiment would unlock new research directions for studying the dynamics of solid-state electronic quantum devices.In this manuscript, we present the development of an experimental setup to generate picosecond voltage pulses in a cryogenic environment for flying qubit applications. A femtosecond laser generates pulses that are injected into optical fibres and integrated at low temperatures. Fabricated on the surface of Low Temperature grown GaAs (LT-GaAs), a photoconductive-switch is co-integrated to the quantum circuit formed on a high mobility two-Dimensional Electron Gas (2DEG). Owing to the extremely fast opto-electronic response of the LT-GaAs, the photo-conductive device converts optical pulses into voltage pulses with a duration as short as a few picoseconds. Using a THz CoPlanar Waveguide (CPW) circuit, the pulse is conveyed toward the 2DEG, where it is used as an ultra-short single-electron source.To perform pump-probe measurement and resolve the dynamic profile of such pulses, an original experimental setup, involving piezo-electric positioners and alignment protocols at low-temperatures, was implemented. As proof of concept, we first report the characterisation at 300 K of electronic pulses with 1.9 ps duration. In a second step, we cool down the system to 4 K and measure 2.3 ps wide pulses, thus expanding the proof of concept to cryogenic environments. Then, by integrating a 2DEG structure along-side the THz circuit, we were able to excite THz plasmons in a Fabry-Pérot cavity. The characteristic frequency of their fundamental mode was compared to an analytical model that revealed information about the carrier density of the electron gas under illumination. In parallel, extensive developments were carried out on the design of CPWs in order to minimise undesirable signal reflections as well as dispersion losses. Finally, with the prospect of measuring and controlling the propagation of picosecond electron pulse in quantum channels directly with ultrafast THz electrostatic gates, the fabrication of the next generation of devices was initiated. This work will pave the way for on-chip integration of picosecond voltage pulses into quantum nanoelectronics devices and ultrafast control of electronic flying qubits
Michal, Vratislav. "Design of CMOS analog integrated circuits as readout electronics for High-TC superconductor and semiconductor terahertz bolometric sensors." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2006. http://tel.archives-ouvertes.fr/tel-00417838.
Kernan, Forest Emerson. "Material Characterization of Zinc Oxide in Bulk and Nanowire Form at Terahertz Frequencies." PDXScholar, 2012. https://pdxscholar.library.pdx.edu/open_access_etds/510.
Delfini, Duccio. "Développement de récepteurs hétérodynes multi-pixels pour les futures missions spatiales." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEO019/document.
The observation of the interstellar medium is very important at mm/(sub)mm/THz frequencies to understand how stars and planets form. Generally such observations rely on heterodyne receivers. These are instruments that achieve very high spectral resolution by down converting a high frequency signal towards a lower frequency one. In a heterodyne receiver the incoming signal is superimposed onto an artificial, well-known, monochromatic signal generated by the local oscillator (LO), chosen to be close to the frequency of the sky signal. The mixer produces the beat frequency signal. It has a frequency equivalent to the difference between the LO and sky signal frequency. Thus the sky signal is translated to a lower frequency, and it is easier to amplify and detect. Usually heterodyne receivers have only one spatial pixel with many frequency channels. Some prototypes have been realized recently with few pixels. Our objective is to develop arrays of hundreds of pixels. In order to do that, some components which compose the heterodyne receiver must be radically rethought, such as the receiving antenna and the LO beam divider.Indeed the receiving antenna generally consists of a double slot antenna on a lens, or a horn antenna. Such antennas are not the best choice for arrays of many pixels since they have to be machined and mounted individually. Instead it is convenient to develop planar structures which can be easily produced in bulk in a single process. In particular we designed and simulated arrays of patch antennas, transmit-arrays and zone plates. The array of patch antennas consists of an array of metallic patches connected via a microstrip line and separated from the ground plane by a dielectric substrate. This configuration takes advantage of the array factor to reduce the beamwidth of the incoming signal in place of the lens. However our simulations showed the array of patch antennas to be quite narrowband for a general purpose application, and quite difficult to realize. For this reason we also analyzed the possibility to use another solution such as the transmit-array. It is an array of several cells which provide a certain phase shift to an incoming wave in order to transform its phase front from planar to spherical. The purpose of the transmit-array is to focus the incoming beam towards a double slot antenna and a mixer placed below it. The simulations showed that a good focusing effect can be reached on a line. We fabricated such a transmit-array and tested it in the laboratory. Because of the small dimensions of a few millimeters these tests are difficult to carry out. Within the measurement error design and simulations are consistent. A third option of a planar lens was studied in the thesis: the zone plate. This is a particular kind of transmit-array which presents only two phase shift of 0° and 180°. The zone plates focus well, but are unfortunately not very efficient.The final part of the thesis introduces a particular kind of beam divider which allows beam splitting of the LO signal towards an array of four very closely packed mixers. To split the beam with such small relative angles is very difficult with the classical Fourier and Dammann grating, for this reason the method we proposed to design such a beam divider is very innovative. Indeed it allows the forming of arbitrary shaped beam patterns, which are not limited by the diffraction orders. Simulations show efficiencies up to 80% which are very good in comparison with classical gratings.In summary in this thesis I have tried several radically different approaches to simplify heterodyne receivers and made a first step towards for large heterodyne arrays with hundreds of pixels
Ahmadivand, Arash. "Plasmonic Nanoplatforms for Biochemical Sensing and Medical Applications." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3576.
Yuan, Jiahui. "Cryogenic operation of silicon-germanium heterojunction bipolar transistors and its relation to scaling and optimization." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33837.
Sinha, Raju. "Tunable, Room Temperature THz Emitters Based on Nonlinear Photonics." FIU Digital Commons, 2017. http://digitalcommons.fiu.edu/etd/3172.
Hessami, Pilehrood Saeid. "Electronic properties of semiconductor nanostructures under terahertz radiation." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20061026.162405/index.html.
Kasjoo, Shahrir Rizal. "Novel electronic nanodevices operating in the terahertz region." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/novel-electronic-nanodevices-operating-in-the-terahertz-region(b5cacff4-272c-44fe-b02d-3d500799d954).html.
Qui, Junyi. "Terahertz spectrometry applied to proteins." Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/24777.
Zimmer, Aaron A. "Terahertz free-electroni laser optical design and simulation." Monterey, California : Naval Postgraduate School, 2010. http://edocs.nps.edu/npspubs/scholarly/theses/2010/Jun/10Jun_Zimmer.pdf.
Thesis Advisor(s): Colson, William B. ; Second Reader: Armstread, Robert L. "June 2010." Description based on title screen as viewed on July 15, 2010. Author(s) subject terms: Free Electron Laser, FEL, Terahertz, THz, FEL Simulations, Beam Clipping. Includes bibliographical references (p. 55-57). Also available in print.
Li, Xian Ph D. Massachusetts Institute of Technology. "Terahertz-field-induced nonlinearity in phonons, electrons and spins." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122713.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 189-210).
In this thesis, I describe work aimed at understanding nonlinear material responses initiated by strong terahertz (THz) field excitation. I discuss two aspects of nonlinear THz spectroscopy in condensed-matter materials: developments of experimental THz capabilities and spectroscopy methods and their applications in investigating ultrafast nonlinear dynamics in different classes of materials. I first describe the THz generation, detection and spectroscopy methods, which are the basis of all of our studies. We have generated strong single- and multi-cycle THz pulses covering several spectral ranges using inorganic and organic crystals and developed linear and nonlinear THz spectroscopy techniques to interrogate light-matter interactions based on different observables and/or symmetry criteria.
We have demonstrated a new method for studying time-domain electron paramagnetic resonance that allows us to measure THz-frequency fine structures of spin energy levels on a tabletop and have developed nonlinear two-dimensional (2D) magnetic resonance spectroscopy to distinguish nonlinear THz-spin interaction pathways. We also show that THz-pump, optical-probe spectroscopy, including THz field-induced second-harmonic generation spectroscopy and THz Kerr effect spectroscopy, can be extended to study phase transitions in quantum paraelectric and topological materials. We have employed the THz methods to drive and detect nonlinear responses from several degrees of freedom in the materials. We have demonstrated collective coherent control over material structure by inducing a quantum paraelectric to ferroelectric phase transition using intense THz electric fields in strontium titanate.
We show that a single-cycle THz field is able to drive ions along the microscopic pathway leading directly to their locations in a new crystalline phase on an ultrafast timescale. We have driven highly nonlinear lattice and electronic responses in a topological crystalline insulator by dynamically perturbing the protecting crystalline symmetry through THz phonon excitation. We have observed oscillations in optical reflectivity that may be associated with electronic gap opening and modulation in the topological surface states. Finally, we have demonstrated nonlinear manipulation of collective spin waves in a canted antiferromagnet using strong THz magnetic fields and we have observed full sets of the second- and third-order nonlinear responses in 2D THz magnetic resonance spectra, which are accurately reproduced in our numerical simulations.
by Xian Li.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Chemistry
Rinzan, Mohamed Buhary. "Threshold extension of gallium arsenide/aluminum gallium arsenide terahetrz detectors and switching in heterostructures." unrestricted, 2006. http://etd.gsu.edu/theses/available/etd-10102006-204618/.
Title from title screen. Unil Perera, committee chair; Donald Edwards, Gennady Cymbaluyk, Mark Stockman, Nikolaus Dietz, Paul Wiita, committee members. Electronic text (348, 24-32 p. : ill.) : digital, PDF file. Description based on contents viewed June 8, 2007. Includes bibliographical references (p. 24-30, second sequence).
Karisan, Yasir. "Full-wave Electromagnetic Modeling of Electronic Device Parasitics for Terahertz Applications." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1419019102.
Hwang, Harold Young. "Nonlinear terahertz spectroscopy of electronic and vibrational responses in condensed matter systems." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/73174.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
In this work, I describe experiments utilizing high-field terahertz (THz) pulses to initiate nonlinear responses in several classes of materials. We have developed several methods for interrogating the nonlinear THz response of materials including collinear and noncollinear THz-pump/THz-probe spectroscopy, and THz-pump/optical probe spectroscopies including THz Kerr effect spectroscopy. We have observed nonlinear free-carrier absorption, occurring through the saturation of free-carrier mobility in bulk semiconductors. We have demonstrated that highly energetic electrons in the conduction band can generate electron-hole pairs in indium antimonide, and have elucidated the dynamics of the carrier generation process. We have observed nonlinear conductivity responses in graphene, showing that a strong THz pulse can heat the electron distribution leading to saturable absorption in the THz range. We have demonstrated THz-induced optical anisotropy in simple liquids, allowing for the measurement of subsequent orientational dynamics. We have driven nonlinear vibrational dynamics in ferroelectrics, demonstrating that the strong anharmonicity of lattice vibrational modes can induce an anisotropic optical response. We have begun to study nonlinear vibrational responses in molecular crystals, which is of importance in mode coupling and energy transfer processes in the THz range. Finally, we have driven nonlinear metamaterial responses in gallium arsenide and vanadium dioxide. In GaAs, we have shown that metamaterial properties may be tuned by an intense THz field if the substrate material (GaAs) is changed by the incident THz pulse, and we have demonstrated carrier multiplication locally in the metamaterial split ring resonator gaps where substantial electric field enhancement occurs. In VO2, we have shown that THz radiation can drive an insulator-to-metal phase transition, opening up new possibilities in the control of the states of matter with THz fields. This work has demonstrated only a few of the capabilities made possible by the interaction of intense THz radiation with matter, and provides a general framework to open up new research in a nascent field.
by Harold Young Hwang.
Ph.D.
Armakavicius, Nerijus. "Study of novel electronic materials by mid-infrared and terahertz optical Hall effect." Licentiate thesis, Linköpings universitet, Halvledarmaterial, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-142220.
Massabeau, Sylvain. "Optical and electronic properties of graphene quantum dots in the Terahertz spectral range." Electronic Thesis or Diss., Sorbonne université, 2020. http://www.theses.fr/2020SORUS445.
The goal of the present thesis is to explore the electronic and optical properties of graphene quantum dots (GQDs) in the THz spectral range. Using tight-binding modelling, we first calculate the energy levels of GQDs of diameters ranging from 6 to 50 nm and analyse the different nature of these energy states. We further calculate their coupling to low energy photons and determine the absorption probability spectra in the THz spectral range. We finally explore how the size, temperature and doping of the GQDs affect their absorption spectra. Secondly, we focus on the experimental investigation of the optical properties of GQDs at THz frequencies, using THz time-domain spectroscopy. Multilayer epitaxial graphene (MEG) samples are probed and then nanostructured in 107 GQDs arrays. We show that the THz response of GQDs with diameters of few tens of nm is mainly characterised by a deep absorption around 6 THz at low and room temperature. These original outcomes are supported by the theoretical analysis and are strongly different from what is observed in MEG. Finally, we study the electronic transport properties of a single GQD in the Coulomb-blockade regime. A single GQD, made of exfoliated graphene encapsulated with hBN layers, is inserted within single electron transistor coupled to a bow-tie THz antenna. Dark transport measurements in the GQD-based transistors show Coulomb blockade regime and excited states of the GQD. Finally, we provide the photoresponse of the GQD in the Coulomb blockade regime under incoherent THz illumination. These results open very exciting perspectives for the development of GQD-based devices for THz photonic applications such as THz lasers
Northeast, David Bernard. "Hot electron bolometer sensors for millimetre-wave and terahertz wave detection." Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6468.
ENGLISH ABSTRACT: The design and simulation of hot electron bolometer sensors for the detection of millimeter and terahertz wave radiation is presented. These devices can be used for the formation of images or for spectroscopy in these frequency ranges. Many molecules resonate and have absorption spectra over these ranges, allowing for the identi cation, non-destructively and at a distance, of the constitution of many di erent materials. The penetrating ability of the radiation makes mm-wave and THz wave detectors ideal for security imaging. The design and simulation of these devices predicts performance as mixers and as interferometers. Manufacturing processes used while fabricating these thin lm devices are outlined and experimental results are reported.
AFRIKAANSE OPSOMMING: Hierdie tesis bespreek die ontwerp en simulasie van warm-elektron bolometers vir die waarneming van millimetergolf- en terahertz-straling. Sodanige toestelle kan in bogenoemde frekwensiebereike gebruik word vir beeldvorming of spektroskopie. Aangesien heelwat molekules binne hierdie bande resoneer, kan die samestelling van 'n verskeidenheid materiale oor 'n afstand en op 'n nie-vernietigende wyse gedenti seer word. Die deurdringingsvermo van millimetergolf- en terahertz-straling maak sulke detektors ideaal vir beeldvorming in veiligheidstoepassings. Met die ontwerp en simulasie van hierdie toestelle word gewys wat hul werkverrigting as mengers en interferometers kan wees. Die prosesse wat gebruik is om hierdie dun lmtoestelle mee te vervaardig word ook bespreek en eksperimentele resultate word aangebied.
Ali, Mubarak. "Design and simulation of planar electronic nanodevices for teraherz and memory applications." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/design-and-simulation-of-planar-electronic-nanodevices-for-teraherz-and-memory-applications(e97fd687-72d1-4807-97c4-cadecfb6defb).html.
Zhou, Min. "A terahertz holography imaging system for concealed weapon detection application." Thesis, Queen Mary, University of London, 2018. http://qmro.qmul.ac.uk/xmlui/handle/123456789/31876.
Yeng, Zang. "A fundamental critical assessment of efficiencies in terahertz time-domain spectroscopy systems." Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/24855.
Eivarsson, Nils, Malin Bohman, Emil Grosfilley, and Axel Lundberg. "Design and Simulation of Terahertz Antenna for Spintronic Applications." Thesis, Uppsala universitet, Institutionen för materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-412982.
Zoth, Christina [Verfasser], and Sergey [Akademischer Betreuer] Ganichev. "Terahertz laser radiation induced opto-electronic effects in HgTe based nanostructures / Christina Zoth. Betreuer: Sergey Ganichev." Regensburg : Universitätsbibliothek Regensburg, 2015. http://d-nb.info/1065445474/34.
Lidberg, Gustav, Karl Pontén, and Johan Millberg. "Design of Optical Magnetic Systems for Terahertz Lensing." Thesis, Uppsala universitet, FREIA, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-445114.
Teramoto, Kensuke. "Generation of intense terahertz surface waves on a metal wire by high-intensity laser driven electrons." Kyoto University, 2020. http://hdl.handle.net/2433/253079.
Hyart, T. (Timo). "Tunable superlattice amplifiers based on dynamics of miniband electrons in electric and magnetic fields." Doctoral thesis, University of Oulu, 2009. http://urn.fi/urn:isbn:9789514260728.
Parkinson, Patrick. "Ultrafast electronic processes at nanoscale organic-inorganic semiconductor interfaces." Thesis, University of Oxford, 2009. http://ora.ox.ac.uk/objects/uuid:e68168c6-bcc0-437d-9133-1bfaf955c80a.
Diaz, Álvarez Adrián. "Surface characterization of III-V semiconductor nanowires : morphological, structural and electronic properties." Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10135/document.
With the size reduction of optoelectronic devices, controlling the surface of semiconductor materials is becoming crucial to optimize their performances. This is particularly true for one-dimensional systems such as semiconductor nanowires that are subject to high surface-to-volume ratio. The aim of this thesis is therefore to perform a comprehensive study of the surface properties of III-V semiconductor nanowires and to determine to what extent they affect their overall properties. Starting with a description of the basic principles that govern their growth in order to obtain nanowire ensembles with a good uniformity, we then highlight a surface science tool, scanning tunneling microscopy, and a surface preparation technique, based on the use of a protective arsenic layer, that are key to further understand the structural and electronic properties of the surface of self-catalysed GaAs and InAs semiconductor nanowires. In the fourth part of this work, we apply these techniques to analyse the structural and electronic properties of GaAs core-shell nanowires consisting of a thin shell grown at low temperature. We show the similarity of the shell properties with low-temperature grown GaAs thin film through the identification of their point defects and finally compare the THz properties of these nanowires with GaAs nanowires. The importance of the shell in the dynamics of the free charge carriers is demonstrated from the analysis of the THz waveforms
Novelli, Fabio. "In search of selective excitations for studying out-of-equilibrium properties in strongly correlated electron systems and high temperature superconductors." Doctoral thesis, Università degli studi di Trieste, 2013. http://hdl.handle.net/10077/8588.
Negli ossidi dei metalli di transizione le correlazioni elettroniche, magnetiche e reticolari sono all’origine di peculiari proprietà fisiche come la resistenza magnetica colossale e la superconduttività ad alta temperatura critica. La spettroscopia risolta in tempo è uno strumento unico per separare il contributo dei singoli gradi di libertà. Inoltre, tale tecnica può essere usata per indurre transizioni di fase non-termiche nella materia condensata. In particolare, scegliendo appositi impulsi pompa in combinazione con impulsi sonda in grado di misurarne gli effetti, è possibile “guidare” la materia nello stato fisico desiderato tramite un’eccitazione selettiva. I primi capitoli della tesi introducono lo stato dell’arte, le tecniche sperimentali e i modelli usati per studiare le proprietà ottiche dei cristalli fuori equilibrio. I capitoli successivi sono dedicati a singoli materiali: abbiamo eseguito misure di riflettività risolte in tempo con pompa nel visibile e sonda ad ampio spettro (1-3 eV) su alcuni isolanti di Mott (YVO3 e La2CuO4) e superconduttori (YBa2Cu3O7-d), e con pompa THz (1 THz~4 meV) su GaAs. YVO3 è un prototipico isolante di Mott e mostra una varietà di fasi caratterizzate da peculiari ordini orbitali e magnetici in funzione della temperatura. In questo sistema le eccitazioni ottiche sono direttamente collegate al grado di libertà orbitale, magnetico o elettronico, ma la loro interpretazione è controversa. Eseguendo misure di riflettività risolte in tempo e frequenza abbiamo dimostrato che le due transizioni ottiche ad energie minori (1.8 eV e 2.4 eV) appartengono alla stessa banda: in particolare, la transizione a 1.8 eV è interpretabile come un eccitone di Hubbard, ovvero uno stato quasi legato stabilizzato da una diminuzione di energia cinetica. Inoltre, abbiamo suggerito l’interpretazione della fase metastabile (che sopravvive almeno fino a 1 ns dopo la foto-eccitazione) come una fase disordinata di spin, e che il materiale potrebbe pertanto essere utilizzato come interruttore magnetico ultra-veloce (F.Novelli et al., Phys. Rev. B 86, 165135, 2012). Per studiare la dipendenza della risposta ottica transiente dei cuprati dalla lunghezza d’onda della pompa ci siamo concentrati sul La2CuO4. I nostri risultati dimostrano che l’effetto degli impulsi di pompa non può sempre essere trattato come semplice perturbazione della temperatura del sotto-sistema elettronico, poiché dinamiche molto diverse vengono rivelate quando l’energia degli impulsi di pompa è maggiore o minore dell’energia del gap di trasferimento di carica, che si trova a circa 2 eV. In particolare foto-eccitare sopra gap è analogo ad un aumento di temperatura, mentre foto-eccitare sotto gap “indurisce” il gap di trasferimento di carica. Ciò suggerisce l’esistenza di eccitazioni a bassa energia che inducono una rinormalizzaizione non termica del gap (in preparazione). Per studiare l’interazione fra grado di libertà vibrazionale e grado di libertà elettronico nei sistemi a forte correlazione elettronica abbiamo utilizzato impulsi di pompa con lunghezza d’onda centrale pari a 800 nm e impulsi di sonda nell’intervallo 400-1200 nm su film sottili di YBa2Cu3O7-d drogato in modo ottimale. Le oscillazioni della riflettività transiente palesano due fononi con frequenze di pochi THz che coinvolgono rispettivamente vibrazioni, pressoché pure, di Ba e Cu. Mentre il modo del rame è indipendente, il modo del bario risulta chiaramente accoppiato alla fase superconduttiva. L’ampiezza delle oscillazioni del modo del bario aumenta sotto la temperatura critica e la sua distribuzione spettrale è modificata quando il condensato viene sciolto dagli impulsi di pompa. I nostri risultati offrono una nuova prospettiva nell’interpretazione della dinamica delle transizioni inter-banda dei cuprati che subiscono forti modificazioni sotto TC (in preparazione). Abbiamo studiato un regime misto nell’interazione fra luce e materia tramite misure risolte in fase dell’effetto Franz-Keldysh nell’arseniuro di gallio. L’effetto Franz-Keldysh consiste nella perturbazione delle proprietà ottiche di un semiconduttore in una regione energetica intorno al gap a seguito dell’applicazione di un campo elettrico. Le misure sono state effettuate con impulsi di pompa ultra corti a singolo ciclo ottico nella regione spettrale del terahertz, e impulsi di sonda ad ampio spettro nella regione spettrale del visibile. Regolando l’intensità degli impulsi di pompa abbiamo studiato sia l’effetto Franz-Keldysh dinamico che un nuovo regime di saturazione in cui la “memoria” è importante, ovvero in cui la risposta ottica intorno al gap dipende da una funzione integrale del campo elettrico applicato. I nostri risultati potrebbero essere utili nell’ambito della strumentazione ottica ultra-veloce (F. Novelli et al., Scientific Reports 3, 1227, 2013). In conclusione, abbiamo dimostrato che le eccitazioni selettive sono certamente possibili in diversi ossidi dei metalli di transizione tramite tecniche spettroscopiche ultra-veloci risolte in tempo e frequenza: importanti informazioni fisiche possono essere ottenute regolando il contenuto energetico degli impulsi laser utilizzati.
XXV Ciclo
1984
Jian, Zhongping. "Terahertz photonic crystals." Thesis, 2006. http://hdl.handle.net/1911/18921.
Johnson, Jon Lars. "Interferometry in terahertz imaging." Thesis, 2001. http://hdl.handle.net/1911/17435.
"Terahertz imaging with compressive sensing." Thesis, 2010. http://hdl.handle.net/1911/61998.
Pearce, Jeremiah Glen. "Multiple scattering of broadband terahertz pulses." Thesis, 2005. http://hdl.handle.net/1911/18797.
Srivastava, Rahul. "Optically detected terahertz resonance spectroscopy of semiconductor nanostructures." Thesis, 2005. http://hdl.handle.net/1911/17831.
Jian, Zhongping. "Space-time cross correlations of diffuse broadband terahertz waves." Thesis, 2003. http://hdl.handle.net/1911/17597.
Pearce, Jeremiah Glen. "The propagation of single-cycle terahertz pulses in random media." Thesis, 2002. http://hdl.handle.net/1911/17538.
Dorney, Timothy Dominic. "Material parameter estimation and imaging with terahertz time-domain spectroscopy." Thesis, 2002. http://hdl.handle.net/1911/18074.