Στη παρούσα διατριβή μελετούμε την αλληλεπίδραση ατόμων αλκαλίων (νατρίου-Na και καλίου-K) με σύμφωνη πηγή ακτινοβολίας (laser). Συγκεκριμένα παρουσιάζουμε: i) Την επίδραση της καταστρεπτικής κβαντικής συμβολής (destructive quantum interference), η οποία εμφανίζεται στη διαδρομή-1, του ατομικού K υπό nsec διφωτονική διέγερση. Η καταστρεπτική κβαντική συμβολή οδηγεί στη γραμμική απόκριση των εσωτερικά παραγόμενων εντάσεων των ακτινοβολιών στις μεταβάσεις των παραγόμενων πεδίων της διαδρομής-1. Το φαινόμενο αυτό μελετάται για διάφορες τιμές των παραμέτρων: της μέγιστης έντασης της διεγείρουσας ακτινοβολίας του laser, του διφωτονικού αποσυντονισμού, της ατομικής πυκνότητας και του μήκους διάδοσης των ακτινοβολιών, όταν οι δύο από τις τρείς αυτές παραμέτρους παραμένουν σταθερές. Επίσης, μελετούμε τις προυποθέσεις του κορεσμού της διαδρομής-1 για ισχυρότερη ένταση του εξωτερικού πεδίου laser και κατόπιν δείχνουμε ότι η διαδρομή-2, εμφανίζεται, έχοντας πρώτα κορεσθεί η διαδρομή-1, στις μικρές ατομικές πυκνότητες. Επιπρόσθετα, παρουσιάζουμε τις προυποθέσεις επαγωγής ενός είδους ατομικής μνήμης (optical free induction memory) όταν ο παλμός laser υποστεί απότομη πτώση στο μέγιστο του (truncated pulse). ii) Τις συνθήκες εκείνες οι οποίες ευθύνονται για την εμφάνιση αξονικής ή/και κωνικής εκπομπής της διαδρομής-1, και διαδρομής-2, αντίστοιχα, για διάφορες ατομικές πυκνότητες, υπό fsec διφωτονική διέγερση του ατομικού K. iii) Την παραγωγή ακτινοβολιών από σύμφωνη παραμετρική μίξη (parametric four-wave mixing) ή και μερικώς σύμφωνο μηχανισμό όπως η ενισχυμένη αυθόρμητη εκπομπή (amplified spontaneous emission) ή υπέρ σκέδαση- Raman (stimulated hyper-Raman scattering), όταν το nsec πεδίο laser διεγείρει με δύο φωτόνια την μετάβαση 4S1/2-6S1/2, καθώς και την μετάβαση 4S1/2-7S1/2, αντίστοιχα. Εστιάζουμε κατά μείζονα λόγο τη μελέτη μας στη διαδρομή-2, στήν μονόδρομη (unidirectional) και στήν αμφίδρομη (bidirectional) διάδοση της ακτινοβολίας του πεδίου laser. iv) Την γέννεση της κωνικής τρίτης αρμονικής (conical third harmonic generation-THG) σε μεταλλικούς ατμούς Na και K υπό fsec διέγερση. Στη περίπτωση του Na (μέσο με κανονική διασπορά) βρίσκουμε ότι η χαρακτηριστική δακτυλοειδή δομή του κώνου της τρίτης αρμονικής οφείλεται στήν επίδραση κυρίως του τανυστικού όρου πέμπτης τάξης ο οποίος σχετίζεται με την μίξη έξι κυμάτων. Ακόμα, δείχνουμε, ότι στη περίπτωση του K (μέσο με αρνητική διασπορά) η εκπομπή μακρινού πεδίου (far field emission) της κωνικής τρίτης αρμονικής, παρουσιάζει ορισμένες διαφοροποιήσεις σε σχέση με αυτή του Na. Το όλο φαινόμενο αντιμετωπίζεται φαινομενολογικά. / In the doctorate dissertation is studied the effect of the wave mixing of laser light with the internally generated fields of the alkali vapors, such as the sodium (Na) and the potassium (K) respectively. Specifically it was studied: ι) The numerical simulation of the four-level system, when a two-photon nsec field excites the transition 4S1/2-6S1/2 of potassium atom. It is shown that the destructive quantum interference is responsible for the reduction of the non-linearity of path-1, in which, the parameters of the system, such as the two-photon detuning, the atomic density and the laser maximum intensity, play an important role. Moreover the saturation of the path-1 has as a consequence the passage of the energy to the atomic path-2, which activates later than the path-1, in low atomic density of atomic K. A truncated excitation pulse is able to induced phenomena of atomic memory in which the providing excitation intensity is able to be stored in the system. The optical free induction memory (OFIM) is observed in the truncated nsec excitation of the transition 4S1/2-6S1/2. This type of atomic memory is studied via the evolution of the density matrix element s12, for specific selection of the two-photon detuning. ii) The conditions which are responsible for the axial or/and conical emission of radiation of path-1 and of path-2, respectively under the fsec two-photon excitation respectively. iii) The production of coherent (parametric four-wave mixing) or/and partially coherent (amplified spontaneous emission or stimulated hyper-Raman scattering) radiation when the nsec laser field excites with two-photons the transition 4S1/2-6S1/2, and the transition 4S1/2-7S1/2, of atomic potassium respectively. It is also studied the emissions of the path-2 in the unidirectional and the bidirectional propagation (counter-propagation) of the laser field in the nsec 4S1/2-6S1/2 two-photon excitation. iv) The conical third harmonic generation (THG) in Na and K vapor under the fsec excitation. It is proved that the third harmonic generation of Na, (normally dispersive medium), in the laser wavelength range of 1770-2200 nm, is mainly a result of six-wave mixing. The fifth order tensor term dominates against the third order term, (which is connected with the four-wave mixing process), as it is shown theoretically. In the case of Κ vapor (negative dispersion medium), in the laser wavelength range of 1200-2180 nm, the observed conical emission appears similarities and dissimilarities with the Na one respectively. The THG generation of Κ interpreted in a phenomenological way.

Cette thèse porte sur l'étude du réseau lacuno-canaliculaire (Lacuno-canalicular Network : LCN) osseux grâce à différentes techniques de microscopie optique. Le LCN correspond à l'empreinte dans la matrice osseuse du réseau ostéocytaire formé de cellules dendritiques (les ostéocytes) interconnectées. Bien qu'il joue un rôle majeur dans la formation, le remodelage et le maintien des propriétés biomécaniques de l'os, les informations sur ce réseau cellulaire dans sa globalité restent limitées. Cela provient notamment de la difficulté à caractériser ce réseau dense et complexeavec une résolution sub-micrométrique sur des échelles allant jusqu'à l'organe entier. Dans cetravail de thèse nous avons cherché à améliorer la caractérisation du LCN en utilisant deux approches : la mise en place d'une méthode d'analyse du LCN à grande échelle à partir dela microscopie confocale d'une part et l'évaluation du potentiel de la microscopienon linéaire pour l'étude du LCN d'autre part.Dans un premier temps nous avons mis au point un protocole allant de la préparation des échantillons jusqu'au traitement des images et à l'analyse des données afin d'optimiser l'imagerie confocale des tissus osseux dans le but d'obtenir une analyse quantitative du réseau à grande échelle. Les résultats préliminaires mettent en évidence une grande variabilité des paramètres du réseau à toutes les échelles révélant la complexité de celui-ci. Cette analyse a été mise en pratique afin d'étudier les variations du LCN à l'échelle d'un fémur entier de souris.Dans un second temps, nous avons évaluer le potentiel de la microscopie optique non linéaire et notamment de la génération de troisième harmonique (THG) pour l'imagerie et l'étude du LCN. Nous avons tout d'abord montré la possibilité de visualiser le LCN, sans marquage fluorescent, grâce à la microscopie THG. A partir de cette preuve de principe nous avons expliqué l'origine des contrastes observés dans l'os par microscopie THG : un signal provenant des porosités et permettant de visualiser le réseau et un signal de fond structuré provenant des interfaces entre les fibrilles de collagène. Nous avons également évaluer les possibilités de la combinaisons de signaux non linéaires, principalement ceux de la THG et de la SHG (génération de seconde harmonique) qui permettent de visualiser simultanément le réseau et la matrice de collagène respectivement. Une corrélation entre la structure du réseau et l'organisation du collagène a pu être établie grâce à la visualisation de ces deux signaux sur de grandes échelles. Enfin des résultats quantitatifs sur le LCN ont pu être obtenus à partir des images THG permettant une étude des effets de la micro-gravité sur la structure de ce réseau. / This thesis focuses on the study of bone lacuno-canalicular network (LCN) using different optical microscopy techniques. The LCN is the porosity network in the bone matrix where the cellular network lie. It is formed of dendritic cells: the osteocytes which are connected to each other. Although it plays a major role in the formation, remodeling and maintenance of biomechanical properties of bone, only little is known about this network as a whole. This can be explain by the difficult characterization of such a dense and complex network with sub-micron resolution and scales up to the entire organ. In this work we have sought to improve the characterization of the LCN using two approaches: the development of a method to analyse the network on large scale using confocal microscopy on one hand, and the assessment of the potential of non linear microscopy technique to study the LCN on the other hand.First, we have developed a protocol from sample preparation to image processing and data analysis to optimize confocal imaging of bone tissue in order to obtain a quantitative large scale analysis of the network. Preliminary results show a wide variation of network parameters at all scales revealing its complexity. This analysis was then used in order to assess changes in the LCN across an entire mice femur.Secondly, we study the potential of the non-linear optical microscopies especially the third harmonic generation (THG) microscopy for imaging and the study of the LCN. Initially, we demonstrated the ability to visualise the LCN without fluorescent labelling using THG microscopy. From this proof of concept we explained the origin of the different ThG microscopy contrasts observed in bone tissue: a signal from the porosities allowing to visualize the network and a structured background signal generated at the interfaces between collagen fibrils. We also assess the possibilities of combinations between different non-linear signals, mainly THG and SHG (second harmonic generation) that can simultaneously image the network and the collagen matrix respectively. A correlation between the network structure and collagen organization has been established using the visualization of these two signals over large scales. Finally quantitative parameters of the LCN were obtained from THG images and applied to study the effects of microgravity on the cellular network structure.

Orientador: Carlos Lenz Cesar / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-22T08:41:16Z (GMT). No. of bitstreams: 1 Thomaz_AndreAlexandrede_D.pdf: 9291787 bytes, checksum: 9554ec1cfb5b3952506ff59b61aec5f9 (MD5) Previous issue date: 2013 / Resumo: A comunidade científica concorda que há grandes chances que a próxima revolução tecnológica virá do controle dos processos biológicos. Grandes mudanças são esperadas, desde como produzimos alimentos até como combatemos as doenças. O controle dos processos biológicos nos permitirá produzir carne sintética para alimentação, produzir biocombustíveis retirando CO2 da atmosfera, produzir órgãos inteiros para transplante e combater de forma eficiente doenças como câncer, por exemplo. Está claro para o nosso grupo que para se obter esses resultados é necessário entender a biologia na sua unidade mais básica: a célula. A partir do entendimento e domínio das reações químicas que acontecem dentro da célula, e mais especificamente do controle do DNA, é que vamos conseguir atingir essas previsões e revolucionar a maneira como vivemos hoje. Com esse pensamento em mente, o objetivo dessa tese foi desenvolver uma plataforma fotônica integrada para estudos de processos celulares. Nós acreditamos que as ferramentas fotônicas são as ferramentas que preenchem todos os requisitos para os estudos de processos celulares, pois possibilitam o acompanhamento dos processos em tempo real sem causar dano as células. As técnicas presentes são: fluorescência excitada por 1 ou 2 fotons, geração de segundo ou terceiro harmônico, pinças ópticas, imagem por tempo de vida da fluorescência e "fluorescence correlation spectroscopy" (FCS). Nesta tese demonstramos como montar essa plataforma integrada e mostramos sua versatilidade com resultados em várias áreas da biologia e também para o estudo de quantum dots. / Abstract: The scientific community believes there is a great chance that the next technological revolution is coming from the control of biological processes. Great changes are expected, from the way we produce food up to the way we fight diseases. The control of biological processes will allow us to produce synthetic meat as food, to produce biofuels extracting CO2 directly from the atmosphere, to produce whole synthetic organs for transplant and to fight diseases, like cancer, in more efficient ways. It is clear to our group that in order to obtain these results it is necessary to understand biology from its most basic unity: the cell. Only from understanding and controlling chemical reactions inside a cell, and more specifically from the DNA controlling, it will be possible to achieve these predictions and cause a revolution in the way we live nowadays. Bearing these thoughts in mind, the objective of this thesis was to develop an integrated photonic platform for study of cellular processes. We believe that photonic tools are the only tools that fulfill all the requeriments for studies of cellular processes because they are capable to follow processes in real time without any damage to the cells. The techniques integrated are: 1 or 2 photon excited fluorescence, second or third harmonic generation, optical tweezers, fluorescence lifetime imaging and fluorescence correlation spectroscopy. In this thesis we demonstraded how to assemble this integrated plataform and we showed its versatility with results from different areas of biology and quantum dots. / Doutorado / Física / Doutor em Ciências

Orientador: Carlos Lenz César / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-09-01T03:43:43Z (GMT). No. of bitstreams: 1 Pelegati_VitorBianchin_D.pdf: 6822381 bytes, checksum: 86749ce34dc184aeb7ed4b4ee47d70b3 (MD5) Previous issue date: 2016 / Resumo: Técnicas de microscopias ópticas são as principais ferramentas capazes de observar células e tecidos biológicos em tempo real e com mínimo dano. Essa área foi revolucionada recentemente através das microscopias confocais de varredura a laser e as microscopias de óptica não linear, naturalmente confocais. Entre os processos não lineares temos, a fluorescência excitada por dois ou mais fótons, geração de segundo harmônico [Second Harmonic Generation - SHG] e terceiro harmônico [Third Harmonic Generation - THG]. SHG e THG são técnicas de óptica não linear coerentes, não necessitam de marcadores exógenos e permitem reconstrução de imagens em três dimensões com resolução espacial subcelular. As técnicas de fluorescência permitem visualizar estruturas específicas no espaço, mas não permitem discriminar as substâncias químicas nas estruturas celulares, e as técnicas de SHG e THG não possuem especificidade química. Espectroscopia Raman possui especificidade química através das propriedades vibracionais das moléculas e pode ser usada como mecanismo de contraste na aquisição de imagens. Comparada com a espectroscopia/microscopia infravermelho, a microscopia Raman traz a informação das vibrações moleculares do infravermelho para o visível, eliminando os problemas da baixa resolução espacial e opacidade das amostras. Entretanto a baixa sensibilidade dessa técnica implica em tempos de aquisição de imagens muito longos, da ordem de horas, inviabilizando acompanhar a dinâmica de processos celulares em tempo real. Como solução para essa baixa sensibilidade do espalhamento Raman espontâneo, surgiu a microscopia por espalhamento Raman Coerente anti-Stokes [Coherent Anti-Stokes Raman Scattering - CARS]. Comparado com Raman espontâneo, a microscopia CARS representa aumento de 4 a 5 ordens de grandeza na sensitividade da técnica, diminuindo os tempos de aquisição ao ponto de viabilizar a aquisição em taxas de vídeos (mais rápido do que 30 quadros por segundo) e estudos em tempo real. Essa tese é dedicada ao estudo experimental e teórico, assim como de algumas aplicações, das técnicas de óptica não linear, com destaque para processos de óptica não linear coerentes. Apresentamos de forma detalhada três sistemas experimentais para a aquisição de imagens de Raman coerente e um sistema integrado com várias técnicas de óptica não linear. Mostramos as primeiras imagens de CARS realizadas no Brasil. Além do CARS convencional, trabalhamos com outra técnica de CARS de ordem mais alta, o CARS cascata [cascade CARS - CCARS], e, no melhor do nosso conhecimento, apresentamos as primeiras imagens internacionais obtidas com essa metodologia. CCARS aumenta o contraste da técnica CARS, diminuindo o fundo não ressonante, um problema que aflige a comunidade científica dedicada ao uso dessa técnica. Além da diminuição do fundo não ressonante, a emissão do CCARS acontece em um comprimento de onda diferente de qualquer outro efeito não linear coerente, significando um acréscimo de complexidade mínimo para sua detecção quando comparado com o CARS. Por último mostramos algumas aplicações realizadas com o sistema experimental desenvolvido para integrar diversas modalidades ópticas em paralelo, especialmente da geração de harmônicos com a fluorescência excitada por dois fótons e suas variantes, como microscopia de tempo de vida de fluorescência (Fluorescence Lifetime Imaging ¿ FLIM) / Abstract: Optical microscopies techniques are the main tools capable of observing cell and biological tissues in real time and with minimum damage. This area have recently been revolutionized by confocal laser scanning microscopies and non-linear microscopies, naturally confocal. Among the non-linear process we have, the two or more photons excited fluorescence, second harmonic generation [SHG] and third harmonic generation [THG]. SHG and THG are coherent nonlinear techniques, they do not require exogenous markers and allow three dimension imaging reconstruction with subcellular resolution. The fluorescence techniques allow visualizing specific structures in space, but do not allow discriminating the chemical substances in cellular structures, SHG and THG techniques do not have chemical specificity. Raman spectroscopy has chemical specificity through the vibrational properties of the molecules and can be used as a contrast mechanism for imaging acquisition. Compared to infrared spectroscopy/microscopy, Raman microscopy brings information about molecular vibration from infrared to visible, eliminating the low resolution and sample opacity problems. However, this technique low sensibility implies in very long imaging acquisition times, order of hours, making it not viable for following cellular process dynamics in real time. As an answer for the spontaneous Raman scattering low sensibility, the coherent anti-Stokes Raman scattering [CARS] emerged. Compared to spontaneous Raman, CARS microscopy presents an increase of 4 to 5 orders of magnitude in the sensitivity of the technique, lowering the acquisition times to the point of making video acquisition (faster than 30 frames per second) and real time studies possible. This thesis is dedicated to the experimental and theoretical study, as well as some applications, of the non-linear techniques, with emphasis on coherent non-linear optical processes. We present in detailed form three experimental systems for the acquisition of coherent Raman images, and a system with the integration of various non-linear techniques. We show the first CARS images acquired in Brazil. In addition to conventional CARS, we worked with other higher order CARS technique, the cascade CARS [CCARS], and, in the best of our knowledge, we present the first international image acquired with this methodology. CCARS increases the contrast from CARS technique, decreasing the non-resonant background, a problem that afflicts the scientific community dedicated to the use of this technique. Besides the decrease of the non-resonant background, the CCARS emission occurs in a different wavelength from any other non-linear coherent effect, meaning a minimum complexity increase for its detection when compared with CARS. Finally we show some applications performed with the experimental system developed to integrate several optical modalities in parallel, especially the generation of harmonics with two photons excitation fluorescence and their variants such as Fluorescence Lifetime Imaging [FLIM] / Doutorado / Física / Doutor em Ciências / 830406/2010 / CAPES

Durch neue Ansätze zur Charakterisierung molekularer und nanokristalliner Materialien spiegelt die vorliegende Arbeit die Synergie von linearer Optik über Ultrakurzzeitphysik zur nichtlinearen Optik wider. Angefangen mit der linearen diffusen Reflektanz (Remission) zur Bestimmung des spektralen Reflexionsvermögens von Pulverpartikeln, erlaubt die hier gezeigte alternative Herangehensweise (s. Kapitel 2) nicht nur ein vereinfachtes Messen der Remission zur Analyse von Materialzusammensetzungen, Verunreinigungen und Co-Dotierungen, sondern eröffnet zudem über Monte-Carlo Simulationen, kombiniert mit der Kubelka-Munk Theorie und der Mie Streuung, auch den Zugang zu dem ansonsten experimentell unzugänglichen Absorptionskoeffizienten von nicht-transluzenten Proben. Die präsentierten Mess- und Simulationsergebnisse an Pulvertabletten aus Rutil-Titandioxid (TiO2) und Cer-dotierten Yttrium Aluminium Granat (YAG:Ce3+) sind mit den bisherigen in der Literatur vorliegenden Ergebnissen konsistent oder zumindest vergleichbar. Auch lassen sich nach Modifikation der Kubelka-Munk Funktion die Bandkanten-Energien Eg der mikro- und nanokristallinen Pulverproben mittels so genannter Tauc Plots verifizieren. Basierend auf einer starken Temperatur- und Konzentrationsabhängigkeit lassen sich die Emissionsspektren der oben genannten YAG:Ce3+-Leuchtstoffe aufgrund von Überlappung oder Verschiebung der energetischen Grundniveaus 2F5/2 und 2F7/2 variieren (s. Kapitel 3). Während sich bei Tieftemperaturen um 19K die doppelbandige Natur der Leuchtstoffe zeigt, verbreitern sich die Emissionsbanden bei Raumtemperatur zu einer Einzelbande, womit eine spektral sehr breite Fluoreszenz einhergeht. Mathematische Entfaltungen dieser Spektren zeigen jeweils den prozentualen Beitrag der Relaxation aus dem untersten angeregten Zustand 5d1 in einen der beiden Grundzustände 2F5/2 und 2F7/2 und ebenso den Einfluss der Temperatur und Cer-Konzentration. Tatsächlich führen die experimentellen Ergebnisse der vorliegenden Arbeit zu der Erkenntnis, dass eine der vier untersuchten YAG:Ce3+-Proben eine erhöhte Cer-Konzentration aufweisen muss. Anders als bei den schwach konzentrierten YAG:Ce3+-Proben ist die spektrale Doppelbande des stark konzentrierten Leuchtstoffs selbst bei 19K nur zu erahnen, während der Beitrag des 5d1 --> 2F7/2 Übergangs auf die Gesamtfluoreszenz retrograd zum 5d1 --> 2F5/2 Übergang mit steigender Temperatur sogar abnimmt. Im direkten Anschluss an die spektrale Vermessung der Proben folgen zeitaufgelöste Lebensdauermessungen zur Bestimmung der Nachleuchtdauern dieser Leuchtstoffe mittels Pikosekunden-Laserpulsen (ps-Pulse) (s. Kapitel 3.3). Auch hier stellen sich Unterschiede zwischen den genannten YAG:Ce3+-Proben heraus und untermauern erneut die Annahme unterschiedlicher Cer-Konzentrationen: Während die Nachleuchtdauer der niedrig konzentrierten Leuchtstoffe von der Temperatur nahezu unberührt bleibt, zeigt sich eine bemerkenswerte Temperaturabhängigkeit des 5d1 --> 2F5/2 Übergangs beim YAG:Ce3+ mit hohem Cer-Gehalt. Auf Basis sämtlicher experimenteller Erkenntnisse und einer ausgiebigen Literaturrecherche kann schließlich eine Fremddotierung der Leuchtstoff-Proben nahezu vollständig ausgeschlossen und ein Energieschema für die vorliegenden YAG:Ce3+-Leuchtstoffe mit den wichtigsten optischen Übergängen erstellt werden. In Hinblick auf potentielle holographische Applikationen wie der optischen Datenspeicherung oder Echtzeit-Holographie erweisen sich die in Polydimethylsiloxan eingebetteten photoschaltbaren Ruthenium-Sulfoxide aufgrund der äußerst geringen Beugungseffizienz von < 10−2 als nicht pragmatisch für die Praxis (s. Kapitel 4). Vergleichbare photoschaltbare Materialien, wie zum Beispiel Natriumnitrosylprussiat, erreichen hingegen Effizienzen von bis zu 100 %. Dennoch zeichnen sich die in Publikation 2 (s. Anhang A.2) vorgestellten Resultate an OSO-PDMS durch ihre äußerst hohe Qualität aus. Sowohl die dynamische Hologramm-Entstehung als auch die Rocking-Kurve folgen den physikalischen Theorien einwandfrei und lassen sich mit den bekannten mathematischen Anpassungen exakt wiedergeben, womit sich entsprechend intrinsische Größen ableiten lassen. Zudem beeindruckt der experimentelle Aufbau mit der präzisen Messung der oftmals nicht detektierbaren Nebenmaxima der gezeigten Rocking-Kurve sowie des Winkel-Multiplexings. Bemerkenswert ist außerdem aus physikalischer Sicht der immense Unterschied zwischen cw- und fs-Holographie. Hier deuten sich nichtlineare Effekte an, die zu der Erkenntnis führen, dass sich die bekannten Theorien mit cw-Lasern nicht ohne Weiteres deckungsgleich auf die Holographie mit ultrakurzen Laserpulsen anwenden lassen. Ein möglicher Erklärungsansatz ist in Kapitel 4.1 beschrieben. Einen praktischen Zweck zur Nutzung nichtlinearer Effekte erfüllt die vorgestellte Messmethode zur Unterscheidung polarer und nicht-polarer Materialien mittels intensiver fs- Puls-Anregung von sogenannten harmonischen (Upconversion-)Nanopartikeln (s. Kapitel 5). Denn anders als die zu Beginn behandelten Leuchtstoffe, weisen die harmonischen Nanopartikel eine starke Anti-Stokes Verschiebung durch Frequenzkonversion zweier oder dreier Photonen zu einem energiereicheren (kurzwelligen) Photon auf. Diese als SHG (second harmonic generation) und THG (third harmonic generation) bekannte Lichtemission wird spektral vermessen, wobei die zu Beginn der Arbeit beschriebenen linearen diffusen Reflektanzmessungen den zu erwartenden Spektralbereich ohne nennenswerte Absorption eingrenzen. Die eigens definierte Gütezahl fR, bestehend aus dem integrierten SHG- und THG-Emissionsspektrum einer Probe, kategorisiert dann die polare (fR > 1) oder nicht-polare (fR << 1) Natur des Materials.