Orientador: Daniel Pereira / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-08T18:30:13Z (GMT). No. of bitstreams: 1 Costa_LeversonFariasLamonier_D.pdf: 15914858 bytes, checksum: 1c9b9d5747ffb493f5451d81d2898051 (MD5) Previous issue date: 2007 / Resumo: Neste trabalho realizamos três importantes etapas: 1) montar e caracterizar um laser selado de 13C02, 2) empregar o laser selado de 13C02 como fonte de bombeamento óptico para a molécula de metanol CH30H, e utilizá-lo pela primeira vez, para excitar o isótopo de metanol 13CH30H para geração de ondas na região do TeraHertz (THz) e 3) Propor "assignments" para as transições THz do CH30H e do 13CH30H. Para excitar as respectivas moléculas de metanol, um tubo comercial selado de 13C02 foi montado e caracterizado num ressonador laser Fabry-Perot. Dois cabeçotes de aluminio foram conectados por 4 barras de invar, separado em 135cm. Em um dos cabeçotes, temos uma grade de difração (150 linhas/mm) na configuração Littrow para selecionar as linhas de emissao do respectivo laser. 0 2° cabeçote suporta um espelho de saída de ZnSe (90% de refletividade com 10m de raio de curvatura) acoplado num PZT para sintonia fina da frequência do laser. No sistema de alimentação, usamos uma fonte de alta tensão comercial (25kV, 8mA) operando em regime DC. Com isso, utilizamos o respectivo laser para excitar as moléculas CH30H e 13CH30H, onde fomos pioneiro no uso do mesmo para bombeio óptico da molécula 13CH30H. Decorrente disso, obtemos os espectros de absorção em torno de cada linha de emissão do 13C02 dos respectivos metanol. Estes dados serviram de referenda para investigação sistemática de novas emissões THz, onde observamos e caracterizamos 12 novas linhas THz do CH30H e 19 do 13CH30H. Todas foram caracterizadas em relação ao seu comprimento de onda, offset, pressao de trabalho, polaridade e intensidade relativa.Utilizando os dados de linhas THz observados por nós, e os espectros de absorção a Transformada de Fourier do CH30H e do 13CH30H, um programa computacional intitulado "Ritz", identificou "assignments" para 4 transições THz do CH30H e 9 emissoes THz para 13CH30H, respectivamente / Abstract: In this work we accomplish three important tasks: to mount and to characterize a laser sealed-off 13C02 to optically pump first time methanol molecules CH30H and 13CH30H for generation of TeraHertz waves; Proposed assignments for transistions THz of the CH30H and 13CH30H. For optical pumping we use a commercial sealed-off 13C02, tube in a homemade Fabry-Perot laser resonator, mounted on two aluminum blocks connected by invar rods and separeted by 1.35m. One block holds a grating (150grooves/mm) used in Littrow configuration to select the emission line, while the second block supports a ZnSe output mirror (90% reflectivity and 10m radius of curvature) mounted on a PZT for fine frequency tuning. We use high voltage power supply (25kV, 8mA) to operate the 13C02 laser in CW regime. A cooling system maintains operation of the laser tube at -10o C. Output powers of l0 W and 1l0 MHz tuning range are typical for lines with higher optical gains. After, molecules CH30H and 13CH30H, optoacoustics spectroscopy (OA) signal, obtained around each sealed-off 13C02 laser line were the starting point to search for THz laser lines. For the more intense OA signal, a systematic investigation was performed to observe and characterize 12 new THz lines of the CH30H and 19 THz emissions of 13CH30H that they had been characterized in wavelength, offset, working pressure, relativepolarity and relative intensity. The available data has been compared a Ritz analysis of the high-resolution Fourier-Transform absorption spectrum of CH30H and 13CH30H, resulting in the assignments for 4 THz transistions of the CH30H and 9 THz emissions for 13CH30H, respectively / Doutorado / Física Atômica e Molecular / Doutor em Ciências

L'absence de source continue monochromatique Térahertz (THz) appropriée constitue un handicap majeur pour le développement des applications associées à cette gamme de longueur d’ondes. En effet, les technologies électroniques et optiques actuelles ne permettent de couvrir qu’une part réduite du spectre électromagnétique THz (0,3-10 THz). Dans ce contexte, la conversion de fréquences optiques, et plus précisément le photo –mélange, est une voie prometteuse pour la génération de signal THz de haute pureté spectrale sur toute la fenêtre du spectre THz. Le photomélange consiste à pomper un dispositif optoélectronique ultrarapide par deux signaux lasers dont les fréquences sont séparées par quelques THz (0,3 à 5 THz). Dans ce travail, nous proposons un nouveau micro-résonateur photonique bifréquence à cavité verticale et monolithique pour la réalisation de source laser bifréquence pour le photomélange. Ce nouveau résonateur est basé sur le couplage de deux résonateurs photoniques, un cristal photonique membranaire résonant d’une part et une cavité Fabry Pérot verticale d’autre part, accordés spectralement, pour réaliser un composant bifréquence. Le couplage optique résultant de l’association de ces deux éléments permet la génération de deux modes hybrides dont la différence de fréquence peut être ajustée en fonction du taux de couplage et donc de la position du cristal photonique dans le micro-résonateur. Le présent travail de thèse porte sur la conception, la fabrication de ce nouveau dispositif bifréquence et son application à la réalisation d’une source laser bi-mode semiconductrice fonctionnant à 1.55dm. / The lack of suitable monochromatic continuous-wave terahertz source consists of one the majors hurdles for terahertz spectrum applications development in various domains. Both electronic and optic technologies don’t allow covering all terahertz electromagnetic spectrum (0.3-10 THz). In this context and in order to generate high spectral purity wave over all THz spectrum window, a well-established technique consists in the photo-mixing procedure, where an ultrafast optoelectronic device is pumped by two laser signals whose frequencies are separated by an offset in the 0.3-5 THz window. In this work, we propose a novel dual-wavelength photonic micro resonator to provide a dual-mode monolithic semiconductor laser for THz generation by photo-mixing instead of the basic photo-mixing approach based on the use of two independent lasers. The novel photonic microresonator associates a vertical Fabry Perot (FP) cavity and photonic crystal membrane (PCM)resonators. A PCM exhibiting a resonant mode at normal incidence is inserted in a FP cavity with a resonant vertical mode at the same wavelength λ0. The resulting strong optical coupling leads to the generation of two mixed modes separated by a frequency difference which can be tuned through the loss rate of the PCM and its position inside the FP cavity. The work of this thesis focuses on the design, the micro-fabrication and the characterization of the dual-frequency resonator and its application to the realization of a single compact and flexible dual-mode semiconductor laser source around 1.55μm.

Ce travail de recherche rapporte l'utilisation de techniques biophotoniques pour investiguer des questions biomédicales, de la recherche fondamentale (interaction champs électriques impulsionnels / cellules) aux études cliniques (toxicité cutanée induite chez les patients traités par des thérapies ciblées).La microspectroscopie confocale Raman et de la microscopie terahertz ont été utilisées pour étudier le processus d’électroperméabilisation cellulaire d'un point de vue moléculaire. Nos résultats démontrent l'implication des protéines. De plus, nous avons montré que la signature Raman des cellules peut être utilisée comme un biomarqueur précis des différents états des cellules exposées aux chocs électriques, correspondant à une électroperméabilisation non détectable, électroperméabilisation et irréversibleEn tant que projet parallèle de ce doctorat, une recherche clinique a été réalisée afin d'étudier la toxicité cutanée induite chez les patients traités par des thérapies anticancéreuses ciblées. Bien que l'efficacité de ces thérapies ne soit pas discutée, de nombreux effets cutanées secondaires graves sont associés. Dans cette étude, nous avons étudié l'opportunité de prédire l’apparition de la toxicité cutanée au moyen de la microspectroscopie Raman confocale réalisée sur la peau des patients. Nous avons réussi à déterminer un nouveau biomarqueur pharmacodynamique spécifique de la toxicité cutanée grâce aux signatures Raman de la peau des patients; alors que l'évaluation dermatologique ou histologique n'a détecté aucune modification. / This research work reports the use of various biophotonics techniques to investigate biomedical questions, from basic research (interaction between pulsed electric fields and cells) to clinical studies (skin toxicity induced in patients treated with targeted anticancer therapies).Confocal Raman microspectroscopy and terahertz microscopy have been used to investigate cell electropermeabilization process from a molecular point of view. Our results demonstrate the involvement of the proteins in cell electropermeabilization. Moreover, we have shown that the Raman signatures of the cells could be used as an accurate biomarker of the different states of the cells exposed to pulsed electric fields, corresponding to no detectable electropermeabilization, reversible and irreversible electropermeabilization.Finally, this doctorate research demonstrates the opportunity to predict skin toxicity induced by targeted anticancer therapies by means of confocal Raman microspectroscopy. We succedded to determine a novel and specific pharmacodynamic biomarker for skin toxicity based on the Raman signatures of the patient’s skin, whereas dermatological or histologicalevaluation did not detect any modifications.

With increasing frequency up to the THz frequency range and the desire to optimize performance of modern applications, precise knowledge of the dielectric material parameters of a substrate being used in a planar application is crucial: High performance of the desired device or circuit can often be achieved only by properly designing it, using specific values for the material properties. Especially the integration of planar devices for very broadband applications at high frequencies often demands specific dielectric properties such as a low permittivity, dispersion and loss, assuring a predictable performance over a broad frequency range. Therefore, material characterization at these frequencies is of interest to the developing THz community, although not a lot of methods suitable in terms of frequency range and measurement setup exist yet. In this work, a comprehensive method for dielectric material parameter determination from S-Parameter measurements of unloaded and loaded planar transmission lines up to THz frequencies is developed. A measurement setup and methodology based on wafer prober measurements is established, which allows for characterization of planar substrates and bulk material samples alike. In comparison with most existing methods, no specialized measurement cell or cumbersome micro-machining of material samples is necessary. The required theory is developed, including a discussion of effective parameter extraction methods from measurement, identification of and correction for undesired transmission line effects such as higher order modes, internal inductance and surface roughness, as well as mapping and modelling procedures based on physical permittivity models and electromagnetic simulations. Due to the general approach and modular structure of the developed method, new models to cover additional aspects or enhance its performance even further are easily implementable. Measurement results from 100 MHz to 500 GHz for planar substrates and from 100 MHz to 220 GHz for bulk material samples emphasize the general applicability of the developed method. It is inherently broadband, while the upper frequency limit is only subject to the fabrication capabilities of modern planar technology (i.e. minimum planar dimensions of transmission lines and height of substrate) and thus is easily extendable to higher frequencies. Furthermore, the developed method is not bound to a specific measurement setup and applicable with other measurement setups as well, as is exemplary presented for a free-space setup using antennas, enabling measurement of large, flat material samples not fitting on the wafer prober. Several substrate and bulk material samples covering a wide range of permittivities and material classes are characterized and compared with reference values from literature and own comparison measurements. The uncertainties for both planar substrate as well as bulk material sample measurements are estimated with a single-digit percentage. For all measurements, the order of magnitude of the dielectric loss tangent can be determined, while the lower resolution boundary for bulk material sample measurements is estimated to 0.01. Concerning measurements in the wafer prober environment, fixture-related issues are a main cause of measurement uncertainty. This topic is discussed as well as the design of on-wafer probe pads and custom calibration standards required for broadband operation at THz frequencies. / Mit zunehmender Erschließung des THz-Frequenzbereichs und der zugehörigen Optimierung moderner Anwendungen ist eine genaue Kenntnis der dielektrischen Materialparameter verwendeter planarer Substrate unabdingbar: Eine hohe Performance angestrebter Bauteile oder Schaltungen kann nur durch einen präzisen Entwurf sichergestellt werden, wofür spezifische Werte für die Materialeigenschaften bekannt sein müssen. Insbesondere die Integration planarer Bauelemente für sehr breitbandige Anwendungen bei hohen Frequenzen bedingt spezifische dielektrische Materialeigenschaften, wie bspw. geringe Permittivität, Dispersion und Verluste, sodass eine vorhersagbare Performance über einen breiten Frequenzbereich sichergestellt werden kann. Materialcharakterisierung bei diesen Frequenzen ist folglich von Interesse für die sich entwickelnde THz-Forschungslandschaft, wenngleich derzeit kaum Verfahren existieren, die geeignet in Bezug auf den Frequenzbereich oder Messaufbau sind. Im Rahmen dieser Arbeit wird ein umfassendes Verfahren zur Bestimmung der dielektrischen Materialparameter aus S-Parameter-Messungen unbelasteter und belasteter planarer Leitungen bis in den THz-Bereich entwickelt. Ein Messaufbau mitsamt Messmethodik basierend auf Wafer Prober-Messungen wird entworfen, welcher die Charakterisierung von planaren Substraten und losen Materialproben ermöglicht. Im Vergleich zu existierenden Verfahren ist weder eine spezielle Messzelle noch eine umständliche Mikrobearbeitung der Materialproben notwendig. Die Entwicklung der hierfür notwendigen Theorie beinhaltet eine Diskussion von Methoden zur Extraktion effektiver Parameter aus Messungen, die Identifikation und Korrektur unerwünschter Leitungseffekte wie bspw. höherer Moden, interner Induktivität und Oberflächenrauhigkeit sowie Zuordnungs- und Modellierungsverfahren basierend auf physikalischen Permittivitätsmodellen und elektromagnetischen Simulationen. Durch den allgemeinen, modularen Ansatz des entwickelten Verfahrens lassen sich neue Modelle zur Berücksichtigung zusätzlicher Effekte oder weiteren Verbesserung der Performance einfach einarbeiten. Messergebnisse von 100 MHz bis 500 GHz für planare Substrate und von 100 MHz bis 220 GHz für lose Materialproben unterstreichen die allgemeine Anwendbarkeit des entwickelten Verfahrens. Es ist inhärent breitbandig, wobei eine obere Frequenzgrenze nur durch die Fertigungstoleranzen moderner planarer Technologien gegeben ist (minimale Leitungsdimensionen und Substrathöhe), sodass es einfach zu höheren Frequenzen hin erweiterbar ist. Weiterhin ist das entwickelte Verfahren nicht an einen bestimmten Messaufbau gebunden und auch mit weiteren Aufbauten anwendbar, wie beispielhaft an einem Freiraum-Aufbau mit Antennen präsentiert wird. Eine Vielzahl planarer Substrate und loser Materialproben, die ein weites Spektrum an Permittivitäten und Materialklassen abdecken, werden charakterisiert und mit Referenzdaten aus der Literatur sowie eigenen Messungen verglichen. Die Messunsicherheiten der Permittivitätsmessungen werden im einstelligen Prozentbereich abgeschätzt und der dielektrische Verlustwinkel kann in seiner Größenordnung bestimmt werden. Aufbaubezogene Einflüsse als eine Hauptursache für Messunsicherheiten am Wafer Prober werden adressiert, ebenso wie der Entwurf von On-Wafer Probe Pads und selbsterstellter Kalibrierstandards, die notwendig sind für den Einsatz bei THz-Frequenzen.

Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Terahertz (THz) radiation is often used in many promising applications such as information and communication technology and airport security. Optimized and adapted terahertz fields hold huge promise for leading this technology further. This study is focused on terahertz time domain spectroscopy (THz-TDS). In THz-TDS the electric field is measured, therefore both amplitude and phase information of the THz pulse can be obtained. We used the pump-probe technique in order to measure a THz pulse from the photoconductive antenna. A pulsed fiber laser with FWHM of ' 100 fs was used for this. The frequency spectrum of the measured THz pulse was obtained via a fast Fourier transform. We studied the principles of the THz pulse generation as well as detection, with a photoconductive antenna as emitter and detector. In this study terahertz spectroscopy has been used to investigate the refractive index and absorption coefficient of different types of materials in the terahertz region. The last part of this study deals with a simple process for material parameter extraction of a polymer sample using commercial software called Teramat1.0. It uses the sample thickness, the reference THz pulse and the transmitted THz pulse to retrieve the complex refractive index of the sample. / AFRIKAANSE OPSOMMING: Terahertz (THz) straling word gereeld gebruik vir belowende toepassings soos inligting en kommunikasie tegnologie en lughawe sekuriteit. Geoptimeerde en aangepaste terahertz velde dra by tot die bevordering van die tegnologie. Hierdie studie fokus op terahertz tyd domein spektroskopie (THz-TDS). In THz-TDS word die elektriese veld gemeet en dus word beide amplitude en fase inligting van die THz puls verkry. Ons gebruik ’n pomp en toets tegniek om die THz puls deur ’n fotogeleidende antenna te bepaal. ’n Gepulseerde vesel laser met FWHM van 100 fs word hiervoor benut. Die frekwensie spektrum van die gemete THz puls word bereken deur ’n vinnige Fourier transvorm te bereken. Die beginsels van die generering en deteksie van THz pulse is bestudeer met ’n fotogeleidende antenna as sender en ontvanger. In die studie is terahertz spektroskopie gebruik om die brekingsindekse en die absorpsie koeffisiënte van verskillende materiale in die terahertz gebied te bepaal. Die laaste gedeelte van die studie handel oor ’n eenvoudige proses om die materiaal parameters van ’n polimeer te bepaal deur gebruik te maak van kommersiële sagteware Teramat 1.0. Die monster dikte, die THz verwysingspuls en die deurgelate puls word gebruik om die komplekse brekingsindeks van die materiaal te bereken.

The contributions of this thesis include designing and analyzing novel medium access control (MAC) protocols for two types of wireless networks: (1) duty-cycling cooperative multi-hop wireless sensor networks (MHWSNs), and (2) single-hop Terahertz networks (TeraNets). For MHWSNs, the specific contributions are two new scalable MAC protocols for alleviating the “energy-hole” problem with cooperative transmission (CT). The energy-hole is known to limit the life of battery-powered MHWSNs. The hole occurs when nodes near the Sink exhaust their energy first because their load is heavier: they must transmit packets they originate and relay packets from and to other nodes farther from the Sink. Effective techniques for extending lifetime in MHWSNs include duty cycling (DC) and, more recently introduced, cooperative transmission (CT) range extension. However, a scalable MAC protocol has not been presented that combines both. From the MAC perspective, conducting CT in an asynchronous duty-cycling network is extremely challenging. On the one hand, the source, the cooperators and the destination need to reach consensus about a wake-up period, during which CT can be performed. This dissertation develops novel MAC protocols that solve the challenge and enable CT in an asynchronous duty-cycling network. On the other hand, the question arises, “Does the energy cost of the MAC cancel out the lifetime benefits of CT range extension?” We show that CT still gives as much as 200% increase in lifetime, in spite of the MAC overhead. The second contribution of this dissertation is a comprehensive analytical framework for MHWSNs. The network performance of a MHWSN is a complex function of the traffic volume, routing protocol, MAC technique, and sensors' harvested energy if sensors are energy-harvesting (EH) enabled. The optimum performance provides a benchmark for heuristic routing and MAC protocols. However, there does not exist such an optimization framework that is able to capture all of these protocol aspects. The problems and performance metrics of non-EH networks and EH networks are different. Because the non-EH nodes depend on a battery, a suitable performance metric is the lifetime, defined as the number of packets delivered upon the first or a portion of nodes' death. Thus, the lifetime is governed by the absorbing states in a controlled dynamic system with finite decision horizon. On the other hand, the lifetime of an EH network is theoretically infinite unless the sensors are broken or destroyed. Therefore, an infinite horizon problem is formulated towards the performance of EH networks. The proposed model departs significantly from past analyses for single-hop networks that do not capture routing and past analyses for multi-hop networks that miss MAC aspects. To our knowledge, this is the first work to model the optimal performance of MHWSNs, by jointly considering MAC layer link admission, routing queuing, energy evolution, and cooperative transmission. The third contribution of this dissertation is a novel MAC protocol for Terahertz (THz) Band wireless networks, which captures the peculiarities of the THz channel and takes advantage of large antenna arrays with fast beam steering capabilities. Communication in THz Band (0.1-10THz) is envisioned as a key wireless technology in the next decade to provide Terabits-per-second links, however, the enabling technology is still in its infancy. Existing MAC protocols designed for classical wireless networks that provide Megabits-per-second to Gigabits-per-second do not scale to THz networks, because they do not capture the peculiarities of the THz Band, e.g., the very high molecular absorption loss or the very high reflection loss at THz Band frequencies. In addition, to overcome the high path loss and extend communication range, the proposed MAC design takes advantage of fast beam steering capabilities provided by the large antenna arrays, in particular, beam-switching at the pulse level.

This thesis proposes a metallic hole array of a rectangular converging-diverging channel (RCDC) shape with extraordinary transmission. We use a three-dimensional (3D) finite element method to analyze the transmission characteristics of two-dimensional metallic hole arrays (2D-MHA) with RCDC. For a straight channel MHA, when the aperture size is reduced, the transmission peaks have a blue-shift. The same result is observed for a smaller gap throat for the RCDC structure. For the rectangular holes with a high length-width ratio, a similar blue-shift in the transmission peaks as well as a narrower full width at half maximum (FWHM) are observed. The asymmetry from the rectangular shape gives this structure high selectivity for light with different polarizations. Furthermore, the RCDC shape gives extra degrees of geometrical variables to 2D-MHA for tuning the location of the transmission peak and FWHM. The tunable transmission property of this structure shows promise for applications in tunable filters, photonic circuits, and biosensors. / text

Condition based monitoring of Thermal Protection Systems (TPS) is necessary for safe operations of space shuttles. In the current research Terahertz radiation (T-ray) has been used to detect mechanical and heat induced damages in TPS tiles. Voids and cracks inside the foam tile are denoted as mechanical damage while property changes due to long and short term exposures of tiles to high heat are denoted as heat induced damage.Ultrasonic waves cannot detect cracks and voids inside the tile because the tile material (silica foam) has high attenuation for ultrasonic energy. Instead, electromagnetic terahertz radiation can easily penetrate into the foam material and detect the internal voids although this electromagnetic radiation finds it difficult to detect delaminations between the foam tile and the substrate plate. Thus these two technologies are complementary to each other for TPS inspection.Ultrasonic and T-ray field modeling in free and mounted tiles with different types of mechanical and thermal damages has been the focus of this research. Shortcomings and limitations of FEM method in modeling 3D problems especially at high-frequencies has been discussed and a newly developed semi-analytical technique called Distributed Point Source Method (DPSM) has been used for this purpose.A FORTRAN code called DPSM3D has been developed to model both ultrasonic and electromagnetic problems using the conventional DPSM method. DPSM has been extended from ultrasonic applications to electromagnetic to model THz Gaussian beams, multilayered dielectrics and Gaussian beam-scatterer interaction problems. Since the conventional DPSM has some drawbacks, to overcome it two modification methods called G-DPSM and ESM have been proposed.The conventional DPSM in the past was only capable of solving time harmonic (frequency domain) problems. In this research DPSM has been extended to model DPSM transient problems. This modified technique has been denoted as t-DPSM.Using DPSM, scattering of focused ultrasonic fields by single and multiple cavities in fluid&solid media is studied. A comparison between the radiation forces generated by the ultrasonic energies reflected from two small cavities versus a single big cavity is also carried out.

The goal of this dissertation work was to develop pulsed terahertz radiation techniques and use them to study different properties of the semiconductor materials and semiconductor devices. Three groups of materials were investigated: GaAsBi, GaAs nanowires, copper-indium chalcogenide. The used techniques are THz-TDS, optical pump – THZ probe, optical pump – optical probe and THz excitation spectral measurements. The main results that were presented in this dissertation are the following: thermal annealing has resulted in the shortening of electron lifetime in GaAsBi to picosecond values, which is important achievement for the application of this material in THz range components. In GaAsBi layers with larger than 10% Bi content absorption bleaching recovering on the picosecond time scale and its saturation can be realized when the wavelengths of the optical signals are as long as 1600 nm. The results of these studies can be applied in the production of SESAM with bismide absorption layer. The samples with GaAs nanowires emit THz radiation several times better than the bulk GaAs substrates due to enhanced light absorption because of localized surface plasmon resonances in GaAs nanowires. THz emission efficiency from thin copper-indium chalcogenide layers strongly depends on their stoichiometry and on the parameters of the top transparent contact layers, thus it can be used for the mapping of built-in electric fields in solar cells made from these layers. / Šio darbo tikslas buvo susipažinti su terahercinių impulsų generavimo ir detektavimo būdais, įsisavinti įvairias terahercinių impulsų panaudojimo metodikas bei pritaikyti jas puslaidininkių medžiagų ir puslaidininkinių prietaisų tyrimui. Buvo tirtos trys medžiagų grupės: GaAsBi, GaAs nanovielutės ir Cu – In chalkogenidai. Tyrimui buvo naudojamos: THz – TDS, optinio žadinimo – THz zondavimo, optinio žadinimo – optinio zondavimo bei THz sužadinimo spektroskopijos metodikos. Pagrindiniai rezultatai aprašyti disertacijoje yra šie: GaAsBi bandinių atkaitinimas stipriai sumažino krūvininkų gyvavimo trukmes, kas yra naudinga THz komponentų gamyboj. Optinio praskaidrėjimo efektas ir pikosekundžių eilės krūvininkų gyvavimo trukmės GaAsBi epitaksiniuose sluoksniuose su 10% ir daugiau Bi atomų stebimas žadinant juos optine spinduliuote, kurios bangos ilgiai siekia iki 1600 nm. Šios GaAsBi bandinių savybės leidžia juos priakyti įsisotinančių sugėriklių veidrodžių gamyboje. Bandiniai su GaAs nanovielutėmis emituoja THz spinduliuotę kelis kartus geriau nei GaAs padėklas, dėl padidėjusios sugerties, kurią skatina paviršinių optinių plazmonų rezonansai GaAs nanovielutėse. THz emisijos efektyvumas iš Cu-In chalkogenidų sluoksnių stipriai priklauso nuo jų stechiometrijos ir viršutinio skaidraus kontakto parametrų, ir gali būti naudojamas saulės elementų, pagamintų šių sluoksnių pagrindu, vidinių elektrinių laukų tyrimui.

Šio darbo tikslas buvo susipažinti su terahercinių impulsų generavimo ir detektavimo būdais, įsisavinti įvairias terahercinių impulsų panaudojimo metodikas bei pritaikyti jas puslaidininkių medžiagų ir puslaidininkinių prietaisų tyrimui. Buvo tirtos trys medžiagų grupės: GaAsBi, GaAs nanovielutės ir Cu – In chalkogenidai. Tyrimui buvo naudojamos: THz – TDS, optinio žadinimo – THz zondavimo, optinio žadinimo – optinio zondavimo bei THz sužadinimo spektroskopijos metodikos. Pagrindiniai rezultatai aprašyti disertacijoje yra šie: GaAsBi bandinių atkaitinimas stipriai sumažino krūvininkų gyvavimo trukmes, kas yra naudinga THz komponentų gamyboj. Optinio praskaidrėjimo efektas ir pikosekundžių eilės krūvininkų gyvavimo trukmės GaAsBi epitaksiniuose sluoksniuose su 10% ir daugiau Bi atomų stebimas žadinant juos optine spinduliuote, kurios bangos ilgiai siekia iki 1600 nm. Šios GaAsBi bandinių savybės leidžia juos priakyti įsisotinančių sugėriklių veidrodžių gamyboje. Bandiniai su GaAs nanovielutėmis emituoja THz spinduliuotę kelis kartus geriau nei GaAs padėklas, dėl padidėjusios sugerties, kurią skatina paviršinių optinių plazmonų rezonansai GaAs nanovielutėse. THz emisijos efektyvumas iš Cu-In chalkogenidų sluoksnių stipriai priklauso nuo jų stechiometrijos ir viršutinio skaidraus kontakto parametrų, ir gali būti naudojamas saulės elementų, pagamintų šių sluoksnių pagrindu, vidinių elektrinių laukų tyrimui. / The goal of this dissertation work was to develop pulsed terahertz radiation techniques and use them to study different properties of the semiconductor materials and semiconductor devices. Three groups of materials were investigated: GaAsBi, GaAs nanowires, copper-indium chalcogenide. The used techniques are THz-TDS, optical pump – THZ probe, optical pump – optical probe and THz excitation spectral measurements. The main results that were presented in this dissertation are the following: thermal annealing has resulted in the shortening of electron lifetime in GaAsBi to picosecond values, which is important achievement for the application of this material in THz range components. In GaAsBi layers with larger than 10% Bi content absorption bleaching recovering on the picosecond time scale and its saturation can be realized when the wavelengths of the optical signals are as long as 1600 nm. The results of these studies can be applied in the production of SESAM with bismide absorption layer. The samples with GaAs nanowires emit THz radiation several times better than the bulk GaAs substrates due to enhanced light absorption because of localized surface plasmon resonances in GaAs nanowires. THz emission efficiency from thin copper-indium chalcogenide layers strongly depends on their stoichiometry and on the parameters of the top transparent contact layers, thus it can be used for the mapping of built-in electric fields in solar cells made from these layers.