Efeitos ópticos não-lineares foram estudados em filmes finos de silício amorfo hidrogenado através da técnica de varredura-Z, que utiliza um único feixe de luz laser de onda contínua, modulado na escala de tempo de milissegundos. Em tal técnica, amostras do material foram deslocadas ao longo da região focal de um feixe com perfil de intensidade gaussiano e comprimento de onda de 532 nm, enquanto a transmitância da luz foi medida no campo distante. Os filmes foram depositados sobre vidro pela técnica PECVD a baixas temperaturas (entre 50 °C e 200 °C) e foi utilizado fósforo como impureza dopante: variando-se a concentração do gás fosfina durante a deposição do material, obtêm-se diferentes quantidades de fósforo incorporado no Si-a:H. Durante a realização da varredura-Z, foi observado o efeito de lente térmica no sinal da transmitância e a resolução temporal do sinal medido possibilitou o ajuste dos dados experimentais ao Modelo de Lente Térmica. A partir dos parâmetros desse ajuste, foi possível determinar a difusividade térmica das amostras (D ~ 3x10-³ cm²/s) e estimar sua condutividade térmica (K ~ 5x10-³ W/Kcm) e seu coeficiente de temperatura do caminho óptico (ds/dT). Além disso, os valores dos deslocamentos de fase do feixe (´teta\') e dos tempos característicos de formação da lente térmica (tc0) foram obtidos. Efeitos ópticos de origem térmica geralmente são indesejados em dispositivos fotônicos e, para evitá-los, o estudo e o conhecimento das propriedades ópticas não-lineares dos materiais que compõem tais dispositivos são de grande importância. Ademais, aplicações em microssensores podem ser baseadas nas propriedades do Si-a:H estudadas neste trabalho, como, por exemplo, sua condutividade térmica. / Nonlinear optical effects have been studied in hydrogenated amorphous silicon films through the single beam Z-scan technique, using a modulated CW laser in the millisecond time-scale regime. In this technique, the samples were moved along the focal region of a focused gaussian laser beam with wavelength of 532 nm, while the light transmittance in the far field was measured. The films were deposited on glass by low temperature PECVD technique (from 50 °C to 200 °C) and phosphorus were used as a dopant impurity: during the material deposition, different concentrations of phosphine gas cause different amounts of incorporated phosphorus into a-Si:H. The thermal lens effect was observed in the transmittance signal, so the experimental data from the time-resolved Z-scan mode could be fitted in the Thermal Lens Model. It was possible to determine the samples thermal diffusivity (D ~ 3x10-³ cm²/s) and to estimate their thermal conductivity (K ~ 5x10-³ W/Kcm) and temperature coefficient of the optical path length change (ds/dT) through those fittings. Besides, the phase shift (\'teta\') and the thermal lens characteristic time (tc0) were achieved. Thermal optical effects are unwanted to photonics devices, therefore studying and knowing these effects is very important to avoid them. Moreover, applications to microsensor devices may use the a-Si:H properties studied in this work as, for example, its thermal conductivity.

Neste trabalho fizemos um estudo da geração de terceiro harmônico (GTH) usando pulsos de femtossegundos (fs). A GTH é uma importante técnica que permite estudar propriedades ópticas não lineares de terceira ordem de materiais. Estudamos a GTH aplicando as técnicas de franjas de Maker e a de varredura-Z em diferentes materiais levando em conta as contribuições de suas interfaces. A técnica de franjas de Maker com GTH permite a determinação de propriedades ópticas lineares e não lineares de volume, mas não de interface, portanto, a técnica de varredura-Z na condição de focalização forte foi implementada para estudar a influência da interface na GTH. Estudamos diversos vidros ópticos (sílica, K10, SK11, LLF1 e LLF6) e também diferentes soluções (acetona, clorofórmio, DMSO e tolueno) em uma cubeta. Em termos de número de interfaces, usando uma lâmina de vidro temos duas, no caso de um sanduíche de dois vidros temos três (entrada, meio e saída) e temos quatro interfaces para a cubeta. Observamos que elas contribuem tanto nas intensidades quanto nos espectros dos terceiros harmônicos (TH) gerados. Dependendo do tipo de interface e do sentido de propagação, tanto a intensidade quanto o espectro do TH são diferentes. Observamos que a reflexão de Fresnel atua significativamente nas diferenças de intensidades da GTH nas interfaces entre dois meios com índices de refração lineares diferentes. Uma interferência construtiva ocorre quando o feixe de laser propaga de um material com índice de refração mais alto para outro com índice mais baixo, aumentando a intensidade do laser e, consequentemente, gerando mais TH. Uma interferência destrutiva ocorre numa propagação oposta. Outro efeito interessante observado foi que, além da magnitude da não linearidade do meio, existem as contribuições da propagação e da modulação de fase cruzada no alargamento espectral do TH. Dessa forma, o alargamento espectral depende da não linearidade do meio e também do sentido de propagação no caso de interfaces. Em resumo, esse estudo nos levou a uma melhor compreensão dos fenômenos não lineares de GTH nas interfaces, e também possibilitou o surgimento de um novo método que pode ser usado para a determinação da susceptibilidade de terceira ordem de materiais. / In this work we did a study of the third-harmonic generation (THG) using femtosecond pulses. The THG is an important technique which allows studying thirdorder nonlinear optical properties of materials. We studied the THG by the Maker fringes and the Z-scan techniques in different materials taking into account their interfaces contributions. The Maker fringes technique with THG allows the determination of the bulk linear and the nonlinear properties, but not of the interface. Therefore, the Z-scan technique in the tight focused condition was implemented to study the interface influences on the THG. We studied several optical glasses (silica, K10, SK11, LLF1 and LLF6) and different solutions (acetone, chloroform, DMSO and toluene) in a cuvette. In term of numbers of interfaces, using a glass slab we have two, in the case of two sandwiched optical glasses we have three (input, middle and output) and for the cuvette we have four interfaces. We have observed that they play an important role on the third-harmonic (TH) intensities and spectra. Depending of the interface type and propagation direction, the TH intensity and spectrum are different. We have observed that the Fresnel reflection has a significant effect on the THG intensity differences between two media with different linear refractive indices. A constructive interference occurs when the laser beam propagates from one material with higher refractive index to one with lower refractive index, increasing the laser intensity and, consequently generating more TH. A destructive interference occurs in the opposite propagation case. Another important effect observed was that, beside the materials nonlinearity magnitude, there are propagation and cross-phase modulation contributions to the TH spectrum broadening. In this way, the spectrum broadening depends on the materials nonlinear properties and the propagation direction on the case of interfaces. In summary, this study leads to a better understanding of the TH nonlinear phenomena, and also, has allowed one new method for third-order nonlinear susceptibility determination.

No presente estudo investigou-se amostras de plasma com DNA livre circulante (DNA LC) por meio da técnica Varredura Z. Esta é uma técnica eficiente na determinação de parâmetros de diferentes materiais, tais como cristais líquidos, ferrofluidos e compostos biológicos. Esta experiência é realizada através da focalização de um feixe laser de perfil gaussiano numa amostra. Na medida em que a amostra se aproxima do foco da lente, a intensidade do feixe aumenta e alcança seu valor máximo no ponto focal, então diminui para pontos distantes do foco. Na região próxima ao ponto focal se amplificam os fenômenos não-lineares. Recentemente foi demonstrado que níveis elevados de DNA LC no plasma ocorrem com frequência em pacientes com vários tipos de câncer, podendo ser utilizados para discriminar pacientes com malignidade de pessoas saudáveis. As amostras de DNA LC, submetidas ao experimento Varredura Z, forneceram respostas ópticas devido ao fenômeno de lente térmica. Os resultados revelaram que a amplitude de lente térmica das amostras extraídas do plasma de pacientes com malignidade difere daquela de doadores sãos. A técnica Varredura Z se mostrou mais vantajosa em relação a outras biológicas porque revelou uma maior diferença entre os grupos estudados e tem o caráter de detectar mudanças estruturais no DNA LC. / In the present study plasma samples with cell-free DNA were investigated by means of the Z-Scan technique. This is a powerfull technique in determining parameters of different materials, such as liquid crystals, ferrofluids and biological compounds. This experiment is performed by focusing a Gaussian profile laser beam on a sample. As the sample approaches the focus of the lens, the intensity of the beam increases and reaches its maximum value at the focal point, then decreases to points distant from the focus. In the region near the focal point non-linear phenomena are amplified. It has recently been demonstrated that high levels of plasma cell-free DNA occur frequently in patients with various cancers and can be used to discriminate patients with malignancy from healthy donors. The cell-free DNA samples, submitted to the Z-Scan experiment, provided optical responses due to the thermal lens phenomenon. The results revealed that the thermal lens amplitude of samples extracted from the plasma of patients with malignancy differs from that of healthy donors. The Z-Scan technique was more advantageous than other biological ones because it revealed a greater difference between the studied groups and has the character of detecting structural changes in cell-free DNA.

Neste trabalho estudamos uma nova classe de materiais ópticos não-lineares, os cristais orgânicos, que possuem potencial para muitas aplicação em dispositivos. Determinamos diferentes propriedades ópticas lineares e não-lineares de três cristais orgânicos: a l-alanina, a l-treonina e a l-lisina. Esses cristais de aminoácido foram escolhidos por apresentarem propriedades de geração de segundo harmônico (GSH) e por serem materiais nunca estudados sob o ponto de vista da óptica não-linear. Estudamos algumas das propriedades ópticas lineares fundamentais desses cristais biaxiais transparentes, pois deles dependem os fenômenos não-lineares sobre os quais são feitas intensas pesquisas. Determinamos as propriedades lineares como os espectros de absorção, os índices de refração, os eixo ópticos, velocidade de propagação da luz num meio anisotrópico e os limiares de dano por radiação. Posteriormente, determinamos as condições de casamento de fase, a eficiência de GSH, e a auto-modulação de fase. A GSH e a auto-modulação de fase pertencem, respectivamente, a processos não-lineares de segunda e de terceira-ordem. Para o estudo de muitas dessas propriedades foram desenvolvidas novas técnicas experimentais. Uma dessas novas técnicas, a varredura-Z oscilante, teve sensibilidade para determinar, pela primeira vez, o índice de refração não oscilante, vez, o índice de refração não linear desses cristais orgânicos. Além disso, como a todos os processos de caracterização envolveram a preparação de amostras, tivemos a oportunidade de criar procedimentos padrões para manipulação e utilização desses novos materiais. / In this work we studied a new class of nonlinear organic crystals that are potential candidates for devices application. We determined several linear and nonlinear optical properties of three organic crystals: l-alanine, l-threonine and l-lysine. These aminoacid. These aminoacid because their nonlinearities were never studied before. We characterized some of the fundamental linear optical properties of these biaxial transparent crystals, because they have influence on nonlinear phenomena that attracted a lot of research. We determined linear properties like absorption spectra, indices of refraction, optical axes, the light speed propagation in anisotropy media and the optical damage threshold. Subsequently, we determined the phase-matching condition for SHG, efficiency of the SHG and self-phase modulation. The SHG and self-phase modulation belongs, respectively, to the second-order and third-order nonlinear processes. To study several of these properties we had to develop some new experimental techniques. One of them, the oscillatory Z-scan, allows enough sensibility to determine, for the first time, the nonlinear refraction index of these organic crystals. Besides, as all these optical characterization involve the preparation of the samples, we had the opportunity to establishing standard procedures for manipulation of these new materials.

Nesta tese estudamos a dinâmica das não linearidades ópticas em compostos orgânicos, mais especificamente em amostras de bis-ftalocianina de itérbio, derivados do álcool furfurílico e compostos azo-aromáticos. Para que a dinâmica dos processos ópticos não lineares pudesse ser investigada nesses materiais, desenvolvemos uma extensão experimental à técnica de varredura-Z convencional, denominada de varredura-Z com trem de pulsos. Nesta técnica, o trem de pulsos de um laser Q-switched/mode-locked é convenientemente empregado para o estudo da dinâmica de processos não lineares no intervalo de 10 a 1000 ns, permitindo a discriminação entre não linearidades rápidas e processos lentos ou acumulativos. Os resultados obtidos através desta técnica nos diversos materiais estudados, complementados com medidas ópticas lineares, tornaram possível a determinação da origem dos processos não lineares refrativos e absorcivos, permitindo também a determinação dos parâmetros espectroscópicos do estado excitado. / This work reports the dynamic nonlinear optical properties of organic compounds, namely, ytterbium bis-phthalocyanine, furfuryl alcohol derivatives and azo-aromatic compounds. In order to carry out this investigation we developed an experimental extension to the standard Z-scan technique, named Z-scan with pulse trains. In this method, pulse trains contained in Q-switched/mode-locked lasers can be advantageously used to study dynamic optical nonlinearities in the 10-1000 ns time interval, allowing the discrimination between fast and slow (cumulative) nonlinear effects. The results obtained in the compounds studied with this technique, complemented with linear optical measurements, permitted the nonlinear refraction and absorption origin to be determined, allowing the characterization of excited state spectroscopic parameters.

Afin d'étudier la contribution des non-linéarités à l'endommagement laser ou de prévoir l'évolution d'une impulsion courte, la mesure précise de l'indice de réfraction non-linéaire est importante. Plusieurs bancs de mesure, reposant sur la méthode de Z-scan, sensibles à de faibles indices de réfraction non-linéaire ont été développés afin d'étudier la contribution des différents mécanismes. <br />Nous avons développé un modèle numérique permettant d'étudier le signal. Nous montrons que le profil spatial du faisceau avait une grande importance sur la mesure. Ensuite la réalisation expérimentale des bancs comprenant tous les moyens de caractérisation nécessaires à une mesure absolue est détaillée. <br />Enfin, une étude de l'indice de réfraction non-linéaire de la silice est entreprise pour différents régimes temporels. Une grande dépendance avec la durée des impulsions et l'absence d'effets thermiques sont constatées ainsi qu'une contribution non négligeable de l'électrostriction en nanoseconde.

Les variations de l'indice de réfraction d'origine électronique, proportionnelles au nombre d'ions actifs du matériau laser portés dans leur état excité et à la variation de polarisabilité entre le niveau excité et le niveau fondamental, peuvent avoir un impact considérable sur les propriétés spatio-temporelles des résonateurs laser. Il est ainsi nécessaire de disposer de méthodes sensibles afin de les évaluer. Ce travail de thèse est donc centré autour de la métrologie de ces effets dits " de population ", afin d'être en mesure de mieux appréhender le comportement des lasers à solide voire d'être capable d'utiliser ces effets pseudo-nonlinéaires pour diverses applications. La première partie de cette thèse consiste donc à quantifier les effets de population dans des cristaux laser dopés Chrome et Ytterbium à l'aide de la technique Z-scan. Dans cette optique, nous avons donc mis en place en expérience résolue en temps afin de nous affranchir des effets thermiques, phénomène inhérent à tout processus de pompage optique. Nous avons par la suite mis au point une technique originale, appelée Baryscan, permettant de mesurer de très faibles variations d'indice et d'atteindre une sensibilité parmi les plus grande rencontrée à ce jour. Cette technique est basée sur l'utilisation d'un Position Sensitive Detector (PSD) et les propriétés non-linéaires des cristaux sont déduites de l'évolution du barycentre du faisceau laser pompe-sonde. Nous présentons de plus des résultats concernant la focalisant diffractive de faisceaux laser à l'aide d'optiques de phase ainsi que des techniques de mise en forme permettant de forcer une cavité laser à osciller sur le mode transverse souhaité.

Demonstration of ultrafast all-optical signal processing (AOSP) using silicon as the active material has been limited by large two-photon absorption loss and long lifetimes of the resulting free carriers. For AOSP at speeds in the terahertz, an order of magnitude faster than that the fastest current electronic counterpart, a class of π-conjugated organic molecules called polymethines provides a promising alternative to silicon as they possess large third-order nonlinearities, and ultrafast polarization response to an incident field. The challenge in the application of polymethines as active nonlinear optical materials for AOSP is in translating their promising molecular properties into bulk material properties. The large linear polarizability and charged nature of the polymethines molecules strongly promote aggregation and phase-separation in solid blends, offsetting their advantageous molecular optical properties. In this work, polymethines’ resistance to deleterious spontaneous symmetry breaking and aggregation was enhanced by substitutions of metal- and chalcogen- containing terminal groups, and rigid steric groups above and below the π-conjugated plane of polymethine chain. The resulting polymethines/amorphous polycarbonate (APC) blend films demonstrated an unprecedentedly high two-photon figure-of-merit, |Re(χ(3))/Im(χ(3))| and low linear loss. The optical quality of the polymethines/APC films was also improved by replacing the commonly-used alkyl ammonium counterions with more polarizable aryl phosphonium counterions with moderate ground state dipole moment. The resulting dye-polymer blend films showed an enhanced near-infrared transparency while its magnitude of the third-order susceptibility, |χ(3)|, showed a good agreement with that extrapolated from the molecular third-order polarizability, γ. For facile integration of these promising organic materials into SOH, the substrate surface was functionalized using silane coupling chemistry for the reduction of surface energy mismatch between the polymer films and the waveguide containing substrates. The optical and SEM micrographs showed vastly improved coverage and infiltration of the microfeatures. Furthermore, to enable the precise engineering of waveguide cross-sectional dimensions for single-mode propagation in the organic cladding, the dispersion curves of the polymethines/polymer blends were generated using prism coupling and ellipsometry. The combined efforts in the development of molecules and materials discussed in the thesis have culminated into a successful identification and optimization of the polymethines dyes and their polymer blends for imminent demonstrations of on-chip AOSP at terahertz speed.

Η παρούσα ειδική ερευνητική εργασία συνιστά μια μελέτη των μη-γραμμικών οπτικών ιδιοτήτων πέντε δειγμάτων νανοσωματιδίων οξειδίων μετάλλων. Κατ’ όνομα πρόκειται για το μονοξείδιο του Κοβαλτίου (CoO), το τετροξείδιο του Μαγγανίου (Mn3O4), το μονοξείδιο του Νικελίου (NiO), τον Αιματίτη (α-Fe2O3) και τον Μαγγεμίτη (γ-Fe2O3). Οι τρίτης τάξης οπτικές μη-γραμμικότητές τους διερευνήθηκαν με την πειραματική τεχνική Z-scan, της οποίας οι βασικές αρχές και οι πειραματικές λεπτομέρειες περιγράφονται στο δεύτερο κεφάλαιο της παρούσης. Ειδικότερα, δίδονται τεχνικές λεπτομέρειες για τις πειραματικές διατάξεις που χρησιμοποιήθηκαν, μελετώνται τα δύο κύρια φαινόμενα που αξιοποιεί η τεχνική, η μη-γραμμική διάθλαση και η μη-γραμμική απορρόφηση και γίνεται σύντομη μαθηματική περιγραφή και παράθεση της διαδικασίας ανάλυσης δεδομένων. Προηγείται των ανωτέρω μια περιεκτική θεωρητική θεμελίωση των βασικών αρχών της μη-γραμμικής οπτικής στο πρώτο κεφάλαιο. Αναπτύσσεται εκ των εξισώσεων Maxwell η μη-γραμμική κυματική εξίσωση. Περιγράφονται οι διεργασίες της γενέσεως δευτέρας αρμονικής, αθροίσματος και διαφοράς συχνοτήτων και διαδοχικά τα βαρύνουσας σημασίας φαινόμενα της αυτό-εστίασης, αυτό-απoεστίασης, κορέσιμης και ανάστροφα κορέσιμης απορρόφησης. Παρατίθεται εν συνεχεία ένας κβαντομηχανικός ορισμός της τρίτης τάξης μη-γραμμικής επιδεκτικότητος και τέλος περιγράφονται αναλυτικά οι μηχανισμοί συνεισφοράς στον μη-γραμμικό δείκτη διάθλασης, από την παραμόρφωση του ηλεκτρονικού νέφους, ως την ηλεκτροσυστολή και τα θερμικά φαινόμενα. Στο τρίτο κεφάλαιο παρουσιάζονται θεωρητικά στοιχεία για τις ιδιότητες των νανοσωματιδίων οξειδίων μετάλλων, την επίδραση του μεγέθους στις εγγενείς ιδιότητες της ύλης και παραδείγματα των πιο ευρέως διαδεδομένων εφαρμογών τους. Εν συντομία δίδονται οι τεχνικές σύνθεσης και οι ενδελεχείς χαρακτηρισμοί που εφαρμόστηκαν με σκοπό να φωτιστούν πλευρές της κρύφιας και ασαφούς φύσης των νανοσωματιδίων. Στο τέταρτο κεφάλαιο παρατίθενται λεπτομερώς οι πειραματικές μετρήσεις, από τα φάσματα απορρόφησης που ελήφθησαν για κάθε παρασκευασθείσα συγκέντρωση διεσπαρμένων νανοσωματιδίων, ως τις γραφικές παραστάσεις που αντιστοιχούν στην τεχνική Z-scan. Συγκεντρώνονται σε πίνακες όλες οι μη-γραμμικές οπτικές παράμετροι που υπολογίστηκαν και λαμβάνει χώρα αναλυτική συζήτηση για τα αποτελέσματα. Τα αποτελέσματα ομαδοποιούνται, εξάγονται ενδιαφέροντα συμπεράσματα και γίνεται σύγκριση με τη βιβλιογραφία. / The present work, a master thesis, is a study of the nonlinear optical properties of five metal oxide nanoparticles, namely Cobalt monoxide (CoO), Manganese tetroxide (Mn3O4), Nickel monoxide (NiO), Hematite (α-Fe2O3) and Maghemite (γ-Fe2O3). Their third ordrer optical nonlinearities were investigated by the means of the Z-scan experimental technique. The basic principles and the experimental details of this technique are described in the second chapter of the present work. Moreover, technical details of the experimental setups used are presented, the two most important phaenomena involved in Z-scan, nonlinear absorption and nonlinear refraction are described, a brief mathematical description and the data analysis details are given. In the first chapter, a comprehensive theoretical basis of the principles of Non-linear Optics is firstly established. Initiating from Maxwell’s equations, the non-linear wave equation is developed step-by-step. The non-linear optical processes of second harmonic generation and sum/difference frequency generation are presented. Consecutively, the very important phaenomena of self-focusing, self-defocusing, saturable and reverse saturable absorption are described. In addition, a quantum-mechanic description of third order nonlinear susceptibility is briefly developed. At last, the contribution mechanisms to the nonlinear refractive index, from the deformation of the electron cloud to the electrostriction and the thermal effects are presented. In the third chapter, some theoretical information about the properties of metal oxides nanoparticles, along with the effects of their size to their behavior and their widely known applications are listed. In brief, the unique details of the synthesis and the assiduous characterization techniques, which were applied in order to illuminate the fringe nature of these nanoscale particles, are given. In the fourth chapter the experimental measurements are apposed in detail, from the UV-Vis-NIR spectra received for every one of the prepared dispersions, to the graphs built on the Z-scan experimental curves. All nonlinear optical parameters deduced, are summed into analytical tables and a lengthy discussion is taking place over all these results. Results are grouped and studied from different perspectives and a bibliographical comparison is done.

The dissertation is dedicated to the detailed numerical modelling of generation dynamics of actively and/or passively Q-switched diode laser longitudinally pumped solid-state lasers, characterization of spatial and temporal laser properties and for the demonstration of application possibility of created minilasers. A detailed theoretical model for the description of generation dynamics using travelling wave approach is presented. In this model more parameters of active laser medium, pump sources and resonator architecture are taken into account. In this thesis the results which show the principal difference between results obtained using the laser travelling wave model and point laser model are presented. Using point laser model the problems of generated pulse timing jitter in passively Q-switched lasers are described and its lowering possibilities using different pumping methods are suggested. In this thesis new, based by the second order moment, laser beam characterisation by knife-edge method is presented. Also laser pulse compression possibilities in tetrachloride CCL4 medium are described. It is showed that using seed signal it is possible to obtain shorter (< 60 ps) and more stable optical pulses. In this thesis application possibilities of created minilasers are presented: the experimental results of the Z-scan measurements obtained using pulses with different pulse shapes for fused silica are presented; also experiments, in which, created minilasers for paper cleaning... [to full text] / Disertacija skirta diodais kaupinamų kietojo kūno lazerių su aktyviąja ir pasyviąja kokybės moduliacija generacijos dinamikos detalesnei skaitmeninei analizei, lazerio impulsų laikinių ir erdvinių parametrų charakterizavimui ir sukurtų minilazerių panaudojimo galimybių demonstracijai. Generacijos dinamikos detalesniai skaitmeniniai analizei, darbe pristatomas sukurtas bėgančiųjų bangų modelis, kuriame atsižvelgiama ne tik į daugelį procesų vykstančių lazerio aktyviajame elemente, bet ir į rezonatoriaus konfigūraciją bei kaupinimo šaltino parametrus. Pateikiami skaitinio modeliavimo rezultatai demonstruojantys šio modelio privalumus lyginant su dažniausiai naudojamu taškiniu lazerio modeliu. Naudojant taškinį lazerio modelį yra nagrinėjama generuojamų impulsų laikinio tirtėjimo problema pasyvios kokybės moduliacijos lazeriuose ir pasiūlyti mažinimo būdai naudojant skirtingus kaupinimo būdus. Darbe taip pat pateiktas naujas, antraisiais momentais pagrįstas, pluošto charakterizavimo judančiu peiliu metodas. Nagrinėjamos lazerių impulsų spūdos galimybės tetrachlorido CCL4 skystyje ir pademonstruota, kad naudojant užkrato signalą galima gauti trumpesnius (< 60 ps) ir stabilesnius optinius impulsus. Darbe pademonstruotos sukurtų minilazerių pritaikymo galimybės: aprašomas netiesinio lūžio rodiklio kvarciniame stikle matavimas Z-skenavimo metodu ir gautų duomenų apdorojimo procedūra įskaitant naudojamų impulsų erdvinę ir laikinę formą; aprašomi eksperimentai, kuriuose sukurti... [toliau žr. visą tekstą]