This diploma thesis follows visualization of snow formations, which are called penitentes. This work includes also collecting the data needed to derive the optical properties of the penitentes material. Which are different phases between snow and ice. For visualization method is used Progressive Transient Photon Beams, that this work implements with the help of SmallUbpb.

This diploma thesis deals with study of resonance modes of plasmonic structures. First part provides an overview of theoretical models, which explain the resonanace modes in plasmonic structures. Next part describes technology of electron beam lithography. First section of experimental part deas with technological processes leading to an improvement of resulting structures made by electron beam lithography that is followed by lift-off process. Last part focuses on a study of reflectance spactra of plasmonic antenas and the identification of resonance modes.

This work focuses on liveness detection for the fingerprint recognition technology. The first part of this thesis describes biometrics, biometric systems, liveness detection and the method for liveness detection is proposed, which is based on spectroscopic characteristics of human skin. The second part describes and summarizes performed experiments. In the end, the results are discussed and further improvements are proposed.

Orientador: Augusto Batagin Neto / Resumo: Radiações ionizantes são atualmente empregadas em diversos setores, inclusive na área da saúde. Contudo, devido às suas características potencialmente danosas à saúde humana, faz-se necessário um monitoramento adequado e contínuo, especialmente no que tange a dosimetria pessoal. Neste contexto, materiais conjugados em solução têm sido apontados como sistemas promissores para a confecção de dosímetros. Apesar das interessantes propriedades destes sistemas, a maioria deles apresenta baixa sensibilidade, o que restringe a sua aplicação efetiva em situações reais. O presente trabalho visa o desenvolvimento de dosímetros baseados em soluções poliméricas e materiais orgânicos de baixo custo relativo. Neste estudo trabalhou-se com dois sistemas principais: i) baseado no polímero poli [(9,9- dioctilfluorenil-2,7,diil)-co-(1,4-vinilienofenileno)] (F8PV) em solução de clorofórmio; e ii) no corante Índigo-carmin (IC) diluído em água, com e sem a presença de nanopartículas de óxido de zinco ou sal inorgânico (NaCl). Amostras com diferentes concentrações foram consideradas e diferentes doses de radiação X foram empregadas. A resposta dosimétrica foi avaliada por meio da análise do espectro de absorção óptica dos sistemas na região do ultravioleta-visível e espectro de infravermelho (FTIR). Os resultados obtidos apontam o sistema F8PV/CHCl3 como um sistema dosimétrico promissor com respostas otimizadas em relação à sistemas poliméricos similares, permitindo a aferição de doses inferiores a... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre

For the first time, a comprehensive characterization of optical, microphysical, and cloud-relevant properties of Central Asian aerosol particles with a state-of-the-art lidar has been performed. This study fills a gap between observations in Eastern Mediterranean (e.g., in Greece, Cyprus, and Israel) and Eastern Asian (e.g, in China, Korea, and Japan) aerosol monitoring. During the Central Asian Dust Experiment (CADEX), an automatic multiwavelength polarization Raman lidar PollyXT was operated in Dushanbe, Tajikistan, from 17 March 2015 until 31 August 2016. During the 18-month campaign, on 487 days, lidar data has been acquired for a time period of at least 3 h. On 308 of these days, the lidar ran even longer than 20 h. 328 manually analyzed profiles of nighttime observations build the data basis of this study and cover well the annual cycle of dust and pollution aerosol layering. Thorough quality assurance and calibration efforts have been made before, during, and after the measurement campaign. With the lidar, vertical profiles of the particle backscatter coefficient at 355 nm, 532 nm, and 1064 nm, of the particle extinction coefficient at 355 nm and 532 nm, and of the particle linear depolarization ratio at 355 nm and 532 nm wavelength were determined. From these quantities, lidar ratios and backscatter-related and extinction-related Ångström exponents were derived. Furthermore, the optical properties were converted to mass concentration and cloud-relevant parameters (CCN and INP concentration) by means of the recently developed lidar technique POLIPHON.

The durability of two solar-selective aluminium titanium oxynitride multilayer coatings was studied under conditions simulating realistic operation of central receiver power plants. The coatings were deposited by cathodic vacuum arc applying an optimized design concept for complete solar-selective coating (SSC) stacks. Compositional, structural and optical characterization of initial and final stacks was performed by scanning electron microscopy, elastic recoil detection, UV-Vis-NIR-IR spectrophotometry and X-Ray diffraction. The design concept of the solar selective coatings was validated by an excellent agreement between simulated and initial experimental stacking order, composition and optical properties. Both SSC stacks were stable in single stage tests of 12 hours at 650°C. At 800°C, they underwent a structural transformation by full oxidation and they lost their solar selectivity. During cyclic durability tests, multilayer 1, comprised of TiN, Al0.64Ti0.36N and an Al1.37Ti0.54O top layer, fulfilled the performance criterion (PC) ≤ 5% for 300 symmetric, 3 hours long cycles at 600°C in air. Multilayer 2, which was constituted of four AlyTi1-y(OxN1-x) layers, met the performance criterion for 250 cycles (750 hours), but was more sensitive to these harsh conditions. With regard to the degradation mechanisms, the coarser microstructure of multilayer 1 is more resistant against oxidation than multilayer 2 with its graded oxygen content. These results confirm that the designed SSCs based on AlyTi1-y(OxN1-x) materials withstand breakdown at 600ºC in air. Therefore, they can be an exciting candidate material for concentrated solar power applications at high temperature.

The design of efficient and stable solar selective coatings for Concentrating Solar Power (CSP) central receivers requires a comprehensive knowledge about the incorporated materials. In this work solar selective coatings were grown by filtered cathodic vacuum arc (FCVA) deposition. The complete stacks consist of an infrared reflection layer, an absorber layer of C:ZrC nanocomposites and an antireflection layer. The Carbon-transition metal nanocomposites were studied as absorber materials because they show appropriate optical properties, i.e. high absorption in the solar region and low thermal emittance. Furthermore metal carbides are thermally and mechanically stabile in air at high temperatures. In order to optimize the absorber layer, the metal content was controlled by adjusting the pulse ratio between the two arc sources. The elemental composition of the absorber layers was determined by Ion Beam Analysis. X-Ray diffraction (XRD) measurements show the formation of metal carbides when the metal content is high enough. The optical properties of the deposited coatings were characterized by spectroscopic ellipsometry (SE). The reflectance spectra of the complete selective coating were simulated with the optical software CODE. Bruggeman effective medium approximation (EMA) was employed to average the dielectric functions of the two components which compose the nanocomposite in the absorber layer. Good agreement was found between simulated and measured reflectance spectra of the solar selective multilayer.

Lignin is one of the main components of wood and plants that acts as a kind of glue providing mechanical strength. It is a main polymer component composed from three phenolic structures, i.e. p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) units. It currently draws a lot of attention due to its eco-friendly. Recently, it has been shown that it is possible to produce lignin nanoparticles, small spherical particle that are composed out of lignin, that could possibly be used to replace the hazardous silver nanoparticles that are today used frequently in numerous applications. Lignin nanoparticles could potenitally also be used as functional coatings, as well as biologically degradable adhesives and float switches. Five samples, of nanoparticles, were investigated in this study. The first contained pure lignin nanoparticles, the second pure silver nanoparticles, and the three remaining samples contained lignin-coated silver nanoparticles, extracted from acetone, tetrahydrofuran (THF), and dimetylformamid (DMF) solvents. All samples were characterized using spectroscopic methods, e.g. infrared- and dark-field imaging, as well as UV-Vis-, fluorescence-, and Raman spectroscopy. In this thesis it was shown that lignin-coated silver nanoparticles exhibit surface plasmon resonance which induces a heat effect upon infrared irradiation. To identify the phenolic structures of lignin, UV-Vis spectroscopy was used. It was found that the spectra of the samples exhibited several intense bands. The objective of the UV-Vis spectroscopy was to examine the absorbance characteristics of the lignin-coated silver nanoparticles. Possible surface plasmon resonance wavelengths were determined, and two of the phenolic structures were identified. In this study, Raman spectroscopy was used to define characteristic bands of the samples. This was done to investigate if the lignin nanoparticles have the same characteristics as bulk lignin. Raman spectroscopy provide structural information of lignin. Furthermore, p-hydroxyphenyl, guaiacyl and syringyl structures could be identified with an excitation wavelength of 532nm. A comparison of the spectra of the lignin-containing samples indicated the the Raman features of the specimens were similar meanwhile almost no signs of silver were present, which might show that the particles were fully covered with lignin. Main lignin bands were identified and assigned. The fluorescent properties of the nanoparticles were investigated by obtaining emission spectra for blue-, green- and UV light excitation. The spectra were deconvoluted into their Gaussian components. Emission spectra were obtained for blue-, green- and UV light excitation. It was found that the fluorescence, after UV light exposure, increased with time of exposure. Dark-field microscopy was used to generate light scattering images of the particles. As a result, optical images with different colors (white, yellow, blue and red) could be revealed. The color information, that is related to the size of the particles, was used to estimate ratios of the different particle sizes. The lignin-coated silver nanoparticles, extracted from acetone, exhibited a strong surface plasmon resonance effect, which could be due to the absorbance at 463nm. The lignin-coated silver nanoparticles, extracted from DMF, exhibited a medium surface plasmon resonance effect, which could be due to the absorbance at 362nm. The lignin-coated silver nanoparticles, extracted from the THF solvent, exhibited a weak surface plasmon resonance effect, which could be due to the absorption at 379-380nm. The pure lignin- and silver nanoparticles merely showed bulk heating but no surface plasmon resonance effect could be detected. / Lignin är en av huvudbeståndsdelarna av trä och plantor som fungerar likt ett lim som ger mekanisk styrka. Lignin är en biopolymer, som består av tre fenylgrupper: p-hydroxifenyl (H), guaiacyl (G) och syringyl (S). På senaste tid har det visat sig att det är möjligt att tillverka lignin nanopartiklar, det är små sfäriska partiklar som är helt gjorda av lignin, som skulle kunna ersätta de miljöfarliga silver nanopartiklarna som i nuläget används i många olika tillämpningar. Lignin nanopartiklar kan potentiellt också användas som funktionella ytbeläggningar, såväl som biologiskt nedbrytbara lim och flottörer. Fem prover, av nanopartiklar, undersöktes i denna studie. Det första provet innehöll lignin nanopartiklar, det andra silver nanopartiklarna, och de tre återstående proverna innehöll ligninbelagda silver nanopartiklar, extraherade från aceton, tetrahydrofuran (THF) och dimetylformamid (DMF). Alla prover karakteriserades med hjälp av spektroskopiska metoder: infraröd- och mörkfältavbildning, liksom UV-Vis-, fluorescens- och Ramanspektroskopi. I denna avhandling visades att ligninbelagda silver nanopartiklar uppvisar ytplasmonsresonans, vilket inducerar en värmeeffekt vid infraröd bestrålning. För att identifiera ligninets fenylgrupper användes UV-Vis-spektroskopi. Det visade sig att spektra från proverna uppvisade flera intensiva band. Målet med UV-Vis-spektroskopin var att undersöka absorptionsegenskaperna hos de ligninbelagda silvernanopartiklarna. Möjliga ytplasmonresonansvåglängder bestämdes och två av fenylgrupperna identifierades. I denna studie användes Ramansspektroskopi för att definiera karakteristiska band för proverna. Detta gjordes för att undersöka om lignin nanopartiklarna har samma egenskaper som bulk lignin. Ramanspektroskopi ger information om ligninets struktur. Vidare identigierades p-hydroxifenyl-, guaiacyl- och syringylstrukturerna med en excitationsvåglängd på 532nm. En jämförelse av spektra för de lignininnehållande proverna indikerade att provernas Raman-kännetecken var liknande medan nästan inga tecken på silver fanns, vilket kan visa att partiklarna var täckta med lignin. Huvudsakliga ligninband kunde identifieras. Fluorescensegenskaperna, hos nanopartiklarna, undersöktes genom de erhållna emissionspektra efter exponering av blå-, grön- och UV-ljus. De erhållna spektra dekonvoluterades till dess gaussiska komponenter. Det visade sig att fluorescensen, efter exponering av UV-ljus, ökade med exponeringstiden. Mörkfältmikroskopi användes för att generera bilder på partiklarna. De resulterade i bilder med olika färger (vitt, gult, blått och rött) som motsvarade olika partikelstorlekar och geometrier. På så sätt kunde färhållandena mellan de olika partikelstorlekarna uppskattas. De ligninbelagda silver-nanopartiklarna, extraherade från aceton-lösningen, uppvisade en stark ytplasmonresonanseffekt, vilket kan bero på absorptionen (från absorptionsspektrat) vid 463nm. De ligninbelagda silver-nanopartiklarna, extraherade från DMF-lösningen, uppvisade en medelstark ytplasmonresonanseffekt, vilket kan bero på absorptionen vid 362nm. De ligninbelagda silver-nanopartiklarna, extraherade från THF-lösningen, uppvisade en svag ytplasmonresonanseffekt, vilket kan bero på absorptionen vid 379-380nm. De rena lignin- och silver-nanopartiklarna uppvisade endast uppvärmning men ingen ytplasmonresonanseffekt.

Several methods have been developed and used to characterize the narrow gap semiconductors Hg^_xCdxTe (HgCdTe) (0.20<x<0.32) and InSb both in the presence of CO2 laser radiation and in the dark. The results have allowed the determination of certain band parameters including the fundamental energy bandgap Eg which is directly related to x, the mole fraction of Cd. In the dark, characterization of several different samples of HgCdTe and InSb were carried out by analyzing the temperature dependence of the Hall coefficient and the magnetic field positions of the magnetophonon extrema from which their x-values were determined. The quality of the magnetophonon spectra is also shown to be related to the inhomogeneity Ax of the HgCdTe samples. One-photon magneto-absorption (OPMA) spectra have been obtained for x ~ 0.2 samples of p-HgCdTe thin films and n-HgCdTe bulk samples. Analysis of the OPMA transition energies allows the x-value to be determined to within « ±0.001. A method is also discussed which can be used to estimate the sample inhomogeneity Ax. Nonlinear optical properties of semiconductors are not only scientifically interesting to study, but are also proving to be technologically important as various nonlinear optical devices are being developed. One of the most valuable nonlinear optical characterization method uses twophoton absorption (TPA). Two techniques using TPA processes were developed and used to measure the cut-off wavelength of several different samples of HgCdTe (x ~ 0.3) from which x-values were determined to within «± 0.0005. Intensity and temperature dependent measurements on impurity and TPA processes have also been carried out and the results are compared with rate equations describing the photo-excited carrier dynamics. These results have yielded important information about the optical and material properties of HgCdTe such as the detection of impurity and trapping levels, TPA coefficients, carrier lifetimes, and recombination mechanisms. TPA and impurity absorption studies were also carried out on n— and p—InSb in order to obtain information about impurity levels, carrier lifetimes, and recombination mechanisms.

Biological organisms, organs and tissues have evolved through natural selection diverse functional and structural traits to accomplish complex tasks. For example, small insects with tiny thermal capacitance have developed tailored spectral properties and behavioral tactics to mitigate rapid changes of body temperatures caused by environmental electromagnetic radiations; neural networks in the brain, through changing the efficacy of synapses, can recognize hidden patterns and correlations in raw data, cluster and classify them, and continuously learn and improve over time. These biological systems are a rich source of bio-inspiration for developing solutions to address engineering challenges. My thesis work focuses on the intersection between photonics and biology and explores three unique biological systems and their technological implications. Beginning with the investigation of butterfly wings, we observed that the wings contain a matrix of living structures, including mechanical and thermal sensory neural cells, hemocytes, pheromone producing organs, , and even “wing hearts”, and that these living structures carry out their specific functions over the entire life span of butterflies but are vulnerable to sustained high temperatures. We discovered that butterflies have evolved heterogeneously thickened wing cuticles and special nanostructured wing scales to locally enhance thermal emissivity so that the regions of the wings containing living structures can better dissipate heat through thermal radiation. Furthermore, we discovered that butterfly wings almost always possess enhanced reflectivity in the near-infrared, which can significantly reduce heating caused by solar radiation. This enhanced near-infrared reflectivity is found to originate from optical scattering at the porous wing scales, especially pale-colored scales underneath the surface layer of colorful ones. Besides these structural adaptations, our bioassays showed that butterflies utilize a number of behavioral strategies to avoid overheating or overcooling of their wings. We found that butterflies can use their wings as a fast and sensitive temperature monitor to detect the direction and strength of sunlight or artificial light applied onto the wings; as such, they can adapt the most suitable postures to minimize overheating of the wings if the illumination is too strong and to warm up the wings when ambident temperatures are insufficient for taking flight. Drawing inspiration from the multi-layered wing scales, which impart coloration to the wings while maintaining their high near-infrared reflectivity, we developed a double-layered, radiative-cooling coating that is able to minimize solar heating while still stay colorful. The second part of my thesis work explored nanostructured fibers and textiles as a novel solution for radiative cooling. The work was motivated by our discovery that the silk fibers produced by the caterpillars of the Madagascan moon moth (Argema mittrei) contain a high density of filamentary air voids, which enable individual fibers of the moth to strongly reflect light over the solar spectrum. This, in combination with natural polymers’ intrinsic high mid-infrared emissivity, provides the cocoons of the moth with remarkable passive radiative-cooling properties. We developed fabrication platforms to produce synthetic fibers with filamentary air voids by modifying both wet spinning and melt extrusion techniques. The melt extrusion approach, in particular, is implemented in an industry-scale fiber extrusion machine for high-throughput, high-yield production. The fabricated nanostructured fibers reproduce the prominent solar reflectivity of the Madagascan moon moth silk fibers and possess high emissivity due to the variety of chemical bonds in the synthetic polymers used. The melt-extruded fibers were twisted into yarns, which were subsequently woven and knitted into fabrics. The finished fabric samples were demonstrated to perform as effective radiative cooling devices compared to conventional white fabrics. Lastly, inspired by how neural networks in the brain form the basis of learning and motivated by how artificial neural networks are implemented in computers, we develop a novel platform of optical neural computing, a smart glass, for object recognition. Our optical neural network takes advantage of strong light-matter interactions with sub-wavelength resolutions in metasurfaces to emulate the layered computations in a biological or artificial neural network. In the simplest implementation of a single-layer smart glass, a metasurface was trained to provide 2D phase modulations that can transform the complex optical wave scattered from an input object into a characteristic intensity distribution pattern on the output plane corresponding to the identity of the object. We experimentally demonstrated the recognition of handwritten numerical digits and letters with different fonts with high accuracies using the smart glass and explored the capability of a polarization-multiplexing smart glass based on birefringent metasurfaces for performing distinct recognition tasks at orthogonal incident polarizations. This optical neural computing platform represents a new paradigm of computation operating at the speed of light with no power consumption and this physical-wave-based computation guarantees data security beyond digital encryption.