Information regarding the structure and function of living tissues and cells is instrumental to the advancement of cell biology and biophysics. Nonlinear optical microscopy can provide such information, but only certain biological structures generate nonlinear optical signals. Therefore, structural specificity can be achieved by introducing labels for nonlinear optical microscopy. Few studies exist in the literature about labels that facilitate harmonic generation, coined "harmonophores". This thesis consists of the first major investigation of harmonophores for third harmonic generation (THG) microscopy. Carotenoids and chlorophylls were investigated as potential harmonophores. Their nonlinear optical properties were studied by the THG ratio technique. In addition, a tunable refractometer was built in order to determine their second hyperpolarizability (γ). At 830 nm excitation wavelength, carotenoids and chlorophylls were found to have large negative γ values however, at 1028 nm, the sign of γ reversed for carotenoids and remained negative for chlorophylls. Consequently, at 1028 nm wavelength, THG signal is canceled with mixtures of carotenoids and chlorophylls. Furthermore, when such molecules are covalently bonded as dyads or interact within photosynthetic pigment-protein complexes, it is found that additive effects with the γ values still play a role, however, the overall γ value is also influenced by the intra-pigment and inter-pigment interaction. The nonlinear optical properties of aggregates containing chlorophylls and carotenoids were the target of subsequent investigations. Carotenoid aggregates were imaged with polarization-dependent second harmonic generation and THG microscopy. Both techniques revealed crystallographic information pertaining to H and J aggregates and β-carotene crystalline aggregates found in orange carrot. In order to demonstrate THG enhancement due to labeling, cultured cells were labeled with carotenoid incorporated liposomes. In addition, Drosophila melanogaster larvae muscle as well as keratin structures in the hair cortex were labeled with β-carotene. Polarization-dependent THG studies may be particularly useful in understanding the structural organization that occurs within biological structures containing carotenoids and chlorophylls such as photosynthetic pigment-protein complexes and carotenoid aggregates in plants and alga. Further, artificial labeling with carotenoids and chlorophylls may be useful in clinical applications since they are nontoxic, nutritionally valuable, and they can aid in visualizing structural changes in cellular components.

This research was mainly focused on the design and optimization of aperture-based structures to achieve the greatest third harmonic conversion efficiency. It was discovered that by tuning the localized surface plasmon resonance to the fundamental beam wavelength, and by tuning the propagating surface plasmons resonance to the Bragg resonance of the aperture arrays, both the directivity and conversion efficiency of the third harmonic signal were enhanced. The influence of the gap plasmon resonance on the third harmonic conversion efficiency of the aperture arrays was also investigated. The resulted third harmonic generation (THG) from an array of annular ring apertures as a closed loop structure were compared to arrays of H-shaped, double nanohole and rectangular apertures as open-loop structures. The H-shaped structure had the greatest conversion efficiency at approximately 0.5 %. Moreover, it was discovered that the maximum THG did not result from the smallest gap; instead, the gap sizes where the scattering and absorption cross sections were equal, led to the greatest THG. The finite difference time domain (FDTD) simulations based on the nonlinear scattering theory were also performed. The simulation results were in good agreement with the experimental data. Moreover, a modified quantum-corrected model was developed to study the electron tunneling effect as a limiting factor of the THG from plasmonic structures in the sub-nanometer regime. / Graduate / 0544 / 0794 / 0752 / 0756 / mrnezami@gmail.com

Master of Science - Science / The theoretical investigation of the Optical Kerr Effect (OKE) and Third- Harmonic Generation (THG) of Au-VO2 nanocomposite thin-films undertaken in this project is motivated by the potential use of the Au-VO2 nanocomposite in nonlinear optical (NLO) devices. NLO devices are a driving force in today fs high technology industry. In this thesis the OKE is estimated and computed and will be compared later to the measured OKE using the Z-scan interferometric laser technique [47]. This is a simple yet highly sensitive single-beam experimental technique used to determine the real part of the dielectric susceptibility. The study of the OKE in these composites has shown that it has a high value, comparable to that found in Au-SiO2, Au-TiO2 and Au-Al2O3 thin-films [29, 33]. This is despite the fact that the Au volumetric concentration in the Au-VO2 composites considered here is 10 percent at most, whereas in the other above mentioned composite thin-films the volumetric concentration range was between 5 − 60 percent. Moreover, it has been demonstrated that the OKE is thermally tunable in the Au-VO2 thin-films, owing to the thermally tunable optical properties of the VO2 [8, 38]. It is found that the magnitude of the OKE is of the order of 10−6 esu when the composite is below 68 0C and it is of the order of 10−7 esu when the nanocomposite thin-film is above 68 0C. The large enhancement of the OKE is due to the surface plasmon resonance (SPR) of the nanogold particles. Its fast response, which is of the order of few picoseconds [4, 6, 7], makes the Au-VO2 nanocomposite a good candidate as a fast thermally tunable optical switch or modulator. The modelling here of high-order harmonic generation in strongly absorbing media, as regards the amplitude of the primary beam, takes into account pump attenuation only, due to the absorption of light by the media. It is not concerned with pump depletion which is a consequence of the transfer of energy to the harmonics and which is small by comparison with attenuation in absorbing media. The modelling is applied to the so-called transmission and reflection configurations. The former refers to the case in which the high-order harmonic wave is monitored in the same direction as the input fundamental wave, whereas the latter describes the situation in which the fundamental wave is in the opposite direction to the high-order harmonic one. To analyse high-order harmonic generation one has to relate the high-order harmonic intensity to the fundamental intensity [1, 9, 10, 34-36]. In so doing, a general formula for analysing high-order harmonic generation is obtained and reduced to the particular case pertaining to THG in strongly absorbing media. The ratio of the third-harmonic intensity to the fundamental intensity is termed the conversion coefficient or the conversion efficiency, and it is denoted by ƒÅ [23, 34]. It is useful in the sense that it expresses quantitatively the amount of input light of frequency ƒÖ converted into light of frequency nƒÖ, where n is the order of nonlinear polarisation [1]. It is found that the THG conversion coefficient is higher the higher the laser intensity. It is thus advantageous to use a pulsed laser, which achieved very high intensities for short periods, separated by long off periods. The net harmonic output in this case is much higher than one would obtain with a continous laser of the same average output. It is found here that ƒÅ is greater in the reflection configuration compared to the transmission one above and below Tt in the photon energy range 1.0 − 3.0 eV, see Fig. 5.1 to 5.8. However, the conversion efficiency for THG in the Au-VO2 nanocomposites for the picoseconds laser illumination we have considered, is still extremely low, and it is difficult to see a potential use for this system as a tunable frequency converter. The situation would become more favorable with the use of femtosecond laser pulses, where for the same pulse energy the intensity is much greater. The laser pulse energy must be limited to avoid excessive heating of the thin-film. The heat generated as a consequence of the illumination of the thin-film by the laser [23] may be controlled by using a simple cooling device which consists of a substrate on which the thin-film is deposited. The choice of such a substrate depends on whether THG is monitored in the transmission or reflection configuration. In the former a transparent substrate must be used (for example diamond) whereas in the latter an opaque substrate may be used (for example Ag). Calculations pertaining to the removal of heat from the illuminated film are reported, and show that thermal control is manageable but only within limits. To avoid a temperature rise of more than 5 0K the peak laser intensity we found must not exceed 7.4 ~105Wcm−2 with a pulse duration of 5 ps.

Genetic algorithm is often used to find the global optimum in a multi-dimensional search problem. Inspired by the natural evolution process, this algorithm employs three reproduction strategies -- cloning, crossover and mutation -- combined with selection, to improve the population as the evolution progresses from generation to generation. Femtosecond laser pulse tailoring, with the use of a pulse shaper, has become an important technology which enables applications in femtochemistry, micromachining and surgery, nonlinear microscopy, and telecommunications. Since a particular pulse shape corresponds to a point in a highly-dimensional parameter space, genetic algorithm is a popular technique for optimal pulse shape control in femtosecond laser experiments. We use genetic algorithm to optimize third harmonic generation (THG), and investigate various pulse shaper options. We test our setup by running the experiment with varied initial conditions and study factors that affect convergence of the algorithm to the optimal pulse shape. Our next step is to use the same setup to control coherent anti-Stocks Raman scattering. The results show that the THG signal has been enhanced.

The use of receptor-targeted lipid microbubbles imaged by ultrasound is an innovative method of detecting and localizing disease. However, since ultrasound requires a medium between the transducer and the object being imaged, it is impractical to apply to an exposed surface in a surgical setting where sterile fields need be maintained. Additionally, the application of an ultrasound gel to the imaging surface may cause the bubbles to collapse. Multiphoton microscopy (MPM) is an emerging tool for accurate imaging of tissues and cells with high resolution and contrast. We have recently developed a novel method for detecting targeted microbubble adherence to the upregulated plectin-receptor on pancreatic tumor cells using MPM. Specifically, the third-harmonic generation response can be used to detect bound microbubbles to various cell types presenting MPM as an alternative and useful imaging method. This is an interesting technique that can potentially be translated as a diagnostic tool for the early detection of cancer and inflammatory disorders.

Orientador: Sérgio Kurokawa / Resumo: Esta dissertação apresenta um estudo realizado sobre o método de recapacitação de linhas de transmissão por injeção de tensão de terceira harmônica (TTH). O método foi publicado em 2017 por Alaei e Khajehoddin como uma proposta mais economicamente viável de elevar a tensão de transmissão sem a necessidade de alterações nas estruturas das linhas de transmissão. A injeção de TTH em linhas convencionais tem como objetivo provocar um achatamento na forma de onda das tensões de fase, causando uma redução em seu valor de pico. O método se mostra vantajoso pelo fato de que a largura das faixas de servidão e as distâncias entre cabos condutores e solo são especificadas com base no valor de pico das tensões de fase. Logo, a redução da tensão de pico não somente permitiria às estruturas existentes transmitirem maior potência como também possibilitaria a construção de novas torres de transmissão com tamanho reduzido e faixas de servidão mais estreitas, tornando uma proposta economicamente atrativa para as companhias de transmissão de energia elétrica. No artigo em que o método de recapacitação em questão foi proposto, os autores realizam análises de tensões e correntes apenas nos terminais das LTs. A contribuição deste trabalho para os estudos do método de recapacitação por injeção de TTH, consiste nas análises feitas através de um modelo de linha de transmissão a parâmetros distribuídos, que permitiu o monitoramento das tensões de fase ao longo da extensão de linhas com diferentes comp... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work presents a study concerning the transmission line uprating method by injection of third harmonic voltage (THV). The method was published in 2017 by Alaei and Khajehoddin as a more economically feasible proposal to raise the transmission voltage level without the requirement for changes in the structural elements of overhead lines. The THV injection in conventional overhead lines aims to flatten the waveform of the phase voltages, resulting in a reduction in its peak values. This represents a significant advantage, since the specification of right-of-way (ROW) width and ground clearance bases on the peak value of the phase voltages. Therefore, a reduction in the peak voltage would not only allow the existing structures to transmit electricity at higher voltages but also the construction of new transmission towers with reduced size and narrower ROW, making it an economically attractive proposal for electric power transmission companies. In the article in which the referred uprating method was proposed, the authors perform voltage and current analyzes only at the TL ends. The contribution of this work to the studies of the uprating method by THV injection consists in the analyzes made through a distributed parameter transmission line model, which allowed the monitoring of the phase voltages along the extension of lines with different lengths, both at steady-state and during the system switching. The results showed that THV injection causes overvoltage along the extent ... (Complete abstract click electronic access below) / Mestre

Printed electronics is a combination of electronics and printing technologies commonly used in the publication industry such as screen, inkjet, and roll to roll printing. The measurements of conductive film particularly the conductive paste is the main objective of this thesis. The conductive paste consists of conductive filler, adhesive and solvent. Each component affects the electrical, and mechanical properties of the finished conductive film product. The measurements of conductive film have three field of study. The first category is the lifetime performance measurement of conductive film using environmental testing. A screen printed carbon, silver and a developmental paste were categorised to environmental testing and third harmonic measurement. The second category is the measurement AC Impedance and DC resistance of conductive ink during cure. During the curing of the pastes, the AC impedance and DC resistance were monitored. A LabVIEW program was developed to control the AC impedance analyser, DC resistance ohmmeter, and convection oven. Samples were measured whilst curing at different curing temperatures and for a range of particle loadings. Particle loading is the percentage of conductive filler against the rest of the chemical in the conductive paste. The last category was defect detection using the combination of electromechanical testing, a Scanning Electron Microscope (SEM) and an Infrared (IR) imaging technique. Printed carbon and silver were mechanically aged by bending the printed structure up to 100 k times. The results from the lifetime performance measurements on carbon, silver and the developmental paste showed the polymer resin behaviour in high humidity and high temperature environments. The increased oxidation rate due to the elevated temperatures affected the conductive particle of certain pastes. The third harmonic testing technique was able to detect failures on conductive film in the form of width reduction. The AC impedance measurement technique could indicate the final resistivity value. The AC impedance measurement was affected by the test frequency used while the ink is in liquid state. Correct test frequency setting will have less noise and less impedance value, vital in predicting the final cured resistance of the printed paste. The curing temperature affects the final cured resistance value while the particle loading affects the rate of curing of conductive film. The electrical measurement on mechanically aged samples showed that the carbon prints have its resistance readings below its initial value while the silver prints resistance increased. SEM images shows that the carbon print indicates no visual damage on the surface after 100 k bent cycle, while physical defects were observed in silver prints. The infrared measurements on carbon prints showed an increase in temperature while developments of heat patches were observed on silver prints. Difference in emissivity values of materials used provided the contrast effect which plays an important role in detecting defect using infrared imaging technique because. Third harmonic application to the printed electronics is new to this field. Normally, testing is done using environmental testing to determine the lifetime performance of the conductive film. This is effective however requires a lot of time and effort to produce a result. AC Impedance is used widely and the application can be seen on cured printed electronics. The application and measurement of AC impedance during cure and DC resistance measurement has indicated initial resistivity values. The measurement has further the effect of using AC impedance on different curing temperature and particle loading. The phase measurement as well has brought insight of degree of curing. The application of infra-red imaging technique to the mechanically aged device has produced a result that DC resistance and SEM imaging failed to detect. Normally DC resistance measurement was used as quality assessment tool but test shows on mechanically aged product failed to detect increase in resistance due to mechanical aging techqnique.

Optical imaging methods have the potential to detect ovarian cancer at an early, curable stage. Optical imaging has the disadvantage that high resolution techniques require access to the tissue of interest, but miniature endoscopes that traverse the natural orifice of the reproductive tract, or access the ovaries and fallopian tubes through a small incision in the vagina wall, can provide a minimally-invasive solution. We have imaged both rodent and human ovaries and fallopian tubes with a variety of endoscope-compatible modalities. The recent development of fiber-coupled femtosecond lasers will enable endoscopic multiphoton microscopy (MPM). We demonstrated two-and three-photon excited fluorescence (2PEF, 3PEF), and second-and third-harmonic generation microscopy (SHG, THG) in human ovarian and fallopian tube tissue. A study was undertaken to understand the mechanisms of contrast in these images. Six patients (normal, cystadenoma, and ovarian adenocarcinoma) provided ovarian and fallopian tube biopsies. The tissue was imaged with three-dimensional optical coherence tomography, multiphoton microscopy, and frozen for histological sectioning. Tissue sections were stained with hematoxylin and eosin, Masson's trichrome, and Sudan black. Approximately 1 mu m resolution images were obtained with an excitation source at 1550 nm. 2PEF signal was absent. SHG signal was mainly from collagen. 3PEF and THG signal came from a variety of sources, including a strong signal from fatty connective tissue and red blood cells. Adenocarcinoma was characterized by loss of SHG signal, whereas cystic abnormalities showed strong SHG. There was limited overlap of two-and three-photon signals, suggesting that three-photon imaging can provide additional information for early diagnosis of ovarian cancer.

The nonlinear optical properties of semiconductor heterostructures, such as GaAsAl/GaAs alloys, are studied with analytic and numerical methods on the basis of quantum mechanics. Particularly, second and third-order nonlinear optical properties of quantum wells described by the various types of confining potentials are considered within the density matrix formalism. We consider a P&ouml / schl-Teller type potential which has been rarely considered in this area. It has a tunable asymmetry parameter, making it a good candidate to investigate the effect of the asymmetry on the nonlinear optical properties. The calculated nonlinear quantities include nonlinear absorption coefficient, second-harmonic generation, optical rectification, third-harmonic generation and the intensity-dependent refractive index. The effects of the DC electric field on the corresponding nonlinearities are also studied. The results are in good agreement with the results obtained in other types of quantum wells, such as square and parabolic quantum wells. The effects of the Coulomb interaction among the electrons on the nonlinear intersubband absorption are considered within the rotating wave approximation. The result is applied to a Si-delta-doped, square quantum well in which the Coulomb interaction among the electrons are relatively important, since there has been no work on the nonlinear absorption spectrum of the Si-delta-doped quantum well. The results are found to be new and interesting, especially when a DC electric field is included in the calculations.

In this study we demonstrate the use of third harmonic (TH) and second harmonic (SH) generation in imaging dental sections. Teeth are the hardest and most indestructible part in human body. The TH and SH greatly facilitate observation of porous structures and collagen within the dental sections, respectively. Strong SH has been found on various biological specimens, such as collagen, potato starch, and skeletal muscles. These materials all possess periodical nano-structures that are often referred as (nonlinear) bio-photonic structures. In particular, collagen is an extra-cellular structural protein and is a major component of bone, cartilage, skin, and other tissues. Collagen fibrils have a triple-helical structure and it is believed that this structure enables collagen to generate SH signal from a wide range of wavelengths in the infrared region. For comparison, microtubule structures within dentin, due to its large index mismatch with surrounding, can be clearly seen with THG imaging. The THG also facilitate observation of prismatic structures in enamel. The successful construction of a multi-photon laser scanning microscope that can operate in both reflection and transmission modes is the key for this study. A femtosecond, sync-pumped optical parametric oscillator (OPO) is used to generate second and third harmonics from dental sections. Dental sections have large index of refraction¡]n~1.68¡^and scatter visible light severely. The employment of excitation wavelength at 1260 nm greatly reduces scattering and absorption within the sample. Its corresponding SH and TH wavelengths are at 630 nm and 420 nm, respectively. Additionally, 3-D structural views are also reconstructed from the optically sectioned images by the use of specialized 3D image processing software.