<p>This thesis explores the use of engineered nonlinear crystals from the KTiOPO4 (KTP) family as the gain material in optical parametric amplifiers (OPAs), with the aim to achieve more knowledge about the benefits and limitations of these devices. The work aims further at extending the possible applications of OPAs by constructing and investigating several efficient and well performing amplifiers.</p><p>An OPA consists of a strong pump source, which transfers its energy to a weak seed beam while propagating through a nonlinear crystal. The crystals employed in this work are members of the KTP family, which are attractive due to their large nonlinear coefficients, high resistance to damage and wide transparency range. The flexibility of OPAs with respect to different wavelength regions and pulse regimes was examined by employing various dissimilar seed and pump sources.</p><p>The possibility to adapt an OPA to a specific pump and seed wavelength and achieve efficient energy conversion between the beams, originates from quasi-phasematching, which is achieved in periodically poled (PP) nonlinear crystals. Quasi-phasematched samples can be obtained by changing the position of certain atoms in a ferroelectric crystal and thereby reversing the spontaneous polarisation.</p><p>In this thesis several material properties of PP crystals from the KTP family were examined. The wavelength and temperature dispersion of the refractive index were determined for PP RbTiOPO4, which is essential for future use of this material. Another experiment helped to increase the insight into the volumes close to domain walls in PP crystals</p><p>Further, several OPAs were built and their ability to efficiently amplify the seed beam without changing its spectral or spatial properties was studied. Small signal gains of up to 55 dB and conversion efficiencies of more than 35 % were achieved for single pass arrangements employing 8 mm long PPKTP crystals. Apart from constructing three setups, which generated powerful nanosecond, picosecond and femtosecond pulses, the possibility to amplify broadband signals was investigated. An increase of the OPA bandwidth by a factor of approximately three was achieved in a noncollinear configuration.</p>

<p>One-dimensional ZnO nanostructures have great potential applications in the fields of optoelectronic and sensor devices. Therefore, it is really important to realize the controllable growth of one-dimensional ZnO nanostructures and investigate their properties. The main points for this thesis are not only to successfully realize the controllable growth of ZnO nonawires, nanorods and quantum dots (QDs), and also investigate the structure and optical properties in detail by the methods of scan electron microscope(SEM), transmission electron microscope(TEM), resonant Raman, photoluminescence(PL) and low-temperature time resolved PL spectrum.</p><p>to grown ZnO nanorod arrays (ZNAs) on Si substrates. Firstly, the effects of ZnO nanoparticles, pH value of chemical solution, angel θ between substrate and beaker bottom on the structures of the samples were symmetrically investigated and the optimized growth condition to grow ZNAs can be concluded as follows: seed layer of ZnO nanoparticles, pH=6 and <em>θ</em>=70°. On the basis of these, the diameter of ZNAs was well controlled from 150nm~40nm through adjusting the diameter and density of the ZnO nanoparticles pretreated on the Si substrates. The experimental results indicated that both diameter and density of ZnO nanoparticles on the substrates determined the diameter of ZNAs. But when the density is higher than the critical value of 2.3×10⁸cm^-2, the density will become the dominant factor to determine the diameter of ZNAs.</p><p>One the other hand, the optical properties of ZNAs were investigated in detail. The Raman and photoluminescence (PL) results showed that after an annealing treatment around 500oC in air atmosphere, the crystal structure and optical properties became much better due to the decrease of surface defects. The resonant Raman measurements excited by 351.1nm not only revealed that the surface defects play a significant role in the as-grown sample, but also suggested that the strong intensity increase of some Raman scatterings was due to both outgoing resonant Raman scattering effect and deep level defects scattering contribution for ZnO nanorods annealed from 500°C to 700°C. It is the first time to the best of our knowledge that the Raman measurements can be used to monitor the change of surface defects and deep level defects in the CBD grown ZnO nanorods. We have also presented, for the first time, a time resolved PL study in CBD grown ZnO nanorods with different diameters. The results show that the decay time of the excitons in the nanorods strongly depends on the diameter of the nanorods. The altered decay time is mainly due to the surface recombination process. The effective time constant related to the surface recombination velocity was deduced. A thermal treatment under 500°C will suppress the surface recombination channel, resulting in an improvement of the optical quality for the ZnO nanorods.</p><p>This thesis not only provides the effective way to control the size of ZNAs, but also obtains some beneficial results in aspects of their optical properties, which builds theoretical and experimental foundation for much better and broader applications of one-dimensional ZnO nanostructures.</p>

In an attempt to develop a more cost-efficient material for solar   energy applications, nano-particles of nickel oxide composite in a silikatmatris manufactured with solar gelmethod and studied structurally by electron microscopy. Furthermore, the thin film optical properties characterized by Variable. Angel Spectroscopic Ellipsometry. Sol gelfilms suitability as a selective absorber surface is also analyzed by optical modeling. / I ett försök att utveckla mer kostnadseffektiva material för solenergitillämpningar har nanopartiklar av nickeloxid inbäddadats i en silikatmatris tillverkats med sol-gelmetoder och undersökts strukturellt med elektronmikroskopi. Vidare har de tunna filmernas optiska egenskaper karakteriserats med vinkelupplöst spektroskopisk ellipsometri. Sol-gelfilmernas lämplighet som en selektiv absorbatoryta har också analyseras genom optisk modellering.

One-dimensional ZnO nanostructures have great potential applications in the fields of optoelectronic and sensor devices. Therefore, it is really important to realize the controllable growth of one-dimensional ZnO nanostructures and investigate their properties. The main points for this thesis are not only to successfully realize the controllable growth of ZnO nonawires, nanorods and quantum dots (QDs), and also investigate the structure and optical properties in detail by the methods of scan electron microscope(SEM), transmission electron microscope(TEM), resonant Raman, photoluminescence(PL) and low-temperature time resolved PL spectrum. to grown ZnO nanorod arrays (ZNAs) on Si substrates. Firstly, the effects of ZnO nanoparticles, pH value of chemical solution, angel θ between substrate and beaker bottom on the structures of the samples were symmetrically investigated and the optimized growth condition to grow ZNAs can be concluded as follows: seed layer of ZnO nanoparticles, pH=6 and θ=70°. On the basis of these, the diameter of ZNAs was well controlled from 150nm~40nm through adjusting the diameter and density of the ZnO nanoparticles pretreated on the Si substrates. The experimental results indicated that both diameter and density of ZnO nanoparticles on the substrates determined the diameter of ZNAs. But when the density is higher than the critical value of 2.3×108cm-2, the density will become the dominant factor to determine the diameter of ZNAs. One the other hand, the optical properties of ZNAs were investigated in detail. The Raman and photoluminescence (PL) results showed that after an annealing treatment around 500oC in air atmosphere, the crystal structure and optical properties became much better due to the decrease of surface defects. The resonant Raman measurements excited by 351.1nm not only revealed that the surface defects play a significant role in the as-grown sample, but also suggested that the strong intensity increase of some Raman scatterings was due to both outgoing resonant Raman scattering effect and deep level defects scattering contribution for ZnO nanorods annealed from 500°C to 700°C. It is the first time to the best of our knowledge that the Raman measurements can be used to monitor the change of surface defects and deep level defects in the CBD grown ZnO nanorods. We have also presented, for the first time, a time resolved PL study in CBD grown ZnO nanorods with different diameters. The results show that the decay time of the excitons in the nanorods strongly depends on the diameter of the nanorods. The altered decay time is mainly due to the surface recombination process. The effective time constant related to the surface recombination velocity was deduced. A thermal treatment under 500°C will suppress the surface recombination channel, resulting in an improvement of the optical quality for the ZnO nanorods. This thesis not only provides the effective way to control the size of ZNAs, but also obtains some beneficial results in aspects of their optical properties, which builds theoretical and experimental foundation for much better and broader applications of one-dimensional ZnO nanostructures.

The Kiirunavaara mine hosts one of the world’s largest apatite-iron ore mineralisations. This ore body has been subject to large amounts of research as well as extensive mining. The ore body is situated between the syenitic foot wall and the rhyodacitic hanging wall, of which consists of differing mineralogy and characteristics. Both these rock masses contain intrusive porphyry dykes, with distinct characteristics of it own. The aim of this study was to analyse 31 samples, mainly in the form of thin sections, and determine the mineralogy and identify eventual microstructures. This was done through the use of optical mineralogy as well as EDS/WDS analysis at the National Microprobe Lab at Uppsala University. The foot wall consists of syenite-porphyry and is dominated by feldspar in both groundmass as well as phenocrysts. Characteristic for the syenite-porphyry is the rounded nodules containing actinolite, titanite, magnetite and chlorite. The hanging wall is defined as quartz-bearing porphyry. It is a rhyodacitic rock with large amounts of feldspar along with green silicates, quartz, titanite and calcite. The intrusive porphyry dyke-rocks share many similarities with the quartz-bearing porphyry, but contain a finer groundmass with larger amounts of clinopyroxene, as well as lower amounts of quartz, magnetite and titanite. Hydrothermal alteration is prevalent in all the types of rock. Alteration minerals such as actinolite, biotite and chlorite are very common within the Kiirunavaara-rocks. The quartz-bearing porphyry displays the most extensive exposure to hydrothermal fluids. The hydrothermal fluids have penetrated several samples, replacing minerals and leaving very few remnant, older minerals. The quartz-bearing porphyry contains the most prominent deformation structures, of varying extent and magnitude. Magmatic flow structures can be seen in the groundmass, as parallel alignment of feldspar and silicate grains. Evidence of solid-state deformation most commonly occurs as pressure shadows around feldspar phenocrysts. / Kiirunavaara-gruvan är belägen vid en av världens största mineraliseringar av apatit-järnmalm. Denna malmkropp har stått i fokus för både omfattande gruvdrift samt genomgripande forskning. Malmkroppen är belägen mellan den syenitiska liggväggen och den ryodacitiska hängväggen, som består av varierande mineralogi och karaktär. Båda av dessa bergmassor innehåller intrusiv gångporfyr med distinkt karaktär. Målet med denna studie var att analysera 31 prover, främst i form av tunnsliper, och bestämma dess mineralogi samt att identifiera eventuella mikrostrukturer. Detta genomfördes genom användning av optisk mineralogi och EDS/WDS-analys vid det nationella mikrosondslaboratioriet vid Uppsala Universitet. Liggväggen består av syenitporfyr och domineras av fältspat i både mellanmassa och som fenokrister. Karaktäristiskt för syenitporfyren är de rundade nodulerna, innehållandes aktinolit, titanit, magnetit och klorit. Hängväggen definieras som kvartsförande porfyr. Det är en ryodacitisk bergart med stora mängder fältspat, gröna silikater, kvarts, titanit och kalcit. Gångporfyren delar många likheter med den kvartsförande porfyren, men består av en finare mellanmassa med större mängd klinopyroxen, samt innehåller mindre mängder kvarts, magnetit och titanit. Hydrotermal omvandling är allmänt förekommande i alla bergarter i Kiirunavaara. Omvandlingsmineral så som aktinolit, biotit och klorit är väldigt vanliga hos Kiirunavaara-bergarterna. Den kvartsförande porfyren uppvisar den mest omfattande exponeringen av hydrotermala vätskor. De hydrotermala vätskorna har penetrerat ett antal prover och därigenom omvandlat mineral, med liten mängd äldre mineral kvar. Den kvartsförande porfyren innehåller de mest prominenta deformationsstrukturer, av olika omfattning och magnitud. Magmatiska flytstrukturer kan observeras i mellanmassan som parallell orientering av fältspat- och silikatkorn. Tecken av fastfasdeformation förekommer främst i form av tryckskuggor runt fältspatsfenokrister.

Med OCR teknologier kan innehållet av ett formulär läsas in, positionen av varje ord och dess innehåll kan extraheras, dock kan relationen mellan orden ej förstås. Denna rapport siktar på att lösa problemet med att berika data från ett strukturerat formulär utan någon förinställd konfiguration genom användandet utav klustring. Detta görs med en kvantitativ metod där mätning av en utvecklad prototyp som räknar antal korrekt klustrade textrutor och en kvalitativ utvärdering. Prototypen fungerar genom att mata en bild av ett ofyllt formulär och en annan bild av ett ifyllt formulär och en annan bild av ett ifyllt formulär som innehåller informationen som ska berikas till en OCR-motor. Utdatan från OCR-motorn körs genom ett efterbearbetningssteg som tillsammans med en modifierad euklidisk algoritm och en oskarp strängsökningsalgoritm kan klustra fältnamn och fältvärden i den ifyllda formulärbilden. Resultatet av prototypen för tre olika formulärstrukturer och 15 olika bilder vardera gav en träffsäkerhet från 100% till 92% beroende på formulärstruktur. Denna rapport kunde visa möjligheten att grupper ihop fältnamn och fältvärden i ett formulera, med andra ord utvinna information från formuläret / With OCR technologies the text in a form can be read, the position of each word and its contents can be extracted, however the relation between the words cannot be understood. This thesis aims to solve the problem of enriching data from a structured form without any pre-set configuration using clustering. This is done using the method of a quantitative measurement of a developed prototype counting correctly clustered text boxes and a qualitative evaluation. The prototype works by feeding an image of an unfilled form and another image of a filled form which contains the data to be enriched to an OCR engine. The OCR engine extracts the text and its positions which is then run through a post-processing step which together with a modified Euclidean and fuzzy string search algorithm, both together is able to cluster field names and field values in the filled in form image. The result of the prototype for three different form structures and 15 different images for each structure ranges from 100% to 92% accuracy depending on form structure. This thesis successfully was able to show the possibility of clustering together names and values in a form i.e., enriching data from the form.

Wavefront sensors for measurements on human eyes are usually large, expensive and difficult to move. A compact wavefront sensor would be more cost-effective and versatile as is could be used in multiple systems. The aim of this thesis was to produce a more compact and portable wavefront sensor. A shorter telescope design for the wavefront sensor was proposed and checked theoretically and with computer simulations. An experimental arrangement comparing the proposed telescope design with a conventional telescope design was constructed. A compact wavefront sensor was built using off-the-shelf components and a few modified components. Tests with the compact wavefront sensor were made both on eye models and on human eyes. The compact wavefront sensor correctly measured the refractive errors of two eye models. It was also possible to perform measurements on human eyes, both in the central and peripheral visual fields, and higher order aberrations were confirmed. For positioning human eyes at the correct distance from the wavefront sensor an additional pupil camera was needed, which was not included in the system. Future improvements for the compact wavefront sensor are discussed. / Vågfrontssensorer för mätningar på ögon är ofta mycket stora, dyra och svåra att transportera. En kompakt vågfrontssensor skulle vara kostnadseffektiv och flexibel eftersom den skulle kunna användas i flera olika system. Målet med detta examensarbete var att producera en mer kompakt och transportabel vågfrontssensor. En kortare teleskopvariant föreslogs och analyserades både teoretiskt och med datorsimuleringar. En experimentell uppsättning gjordes också för att jämföra den kortare teleskopdesignen med ett sedvanligt vågfrontssensorteleskop. En kompakt vågfrontssensor byggdes med standardkomponenter samt med några modifierade standardkomponenter. Tester med den kompakta vågfrontssensorn gjordes både på ögonmodeller och mänskliga ögon. Den kompakta vågfrontssensorn gav korrekta mätvärden på brytningsfelen på ögonmodellerna. Det gick bra att genomföra mätningar på mänskliga ögon, både i centrala och perifera synfältet, och högre ordningens aberrationer bekräftades. För att placera mänskliga ögon på korrekt avstånd från vågfrontssensorn krävdes en extra pupillkamera, som inte var inkluderad i den kompakta vågfrontssensorn. Framtida förbättringar för den kompakta vågfrontssensorn diskuteras.

I dagens affärsmiljö strävar många organisationer efter att automatisera processen för att hämta information från fakturor. Målet är att göra hanteringen av stora mängder fakturor mer effektiv. Trots detta möter man utmaningar på grund av den varierande strukturen hos fakturor. Placeringen och formatet för information kan variera betydligt mellan olika fakturor, vilket skapar komplexitet och hinder vid automatiserad utvinning av fakturainformation. Dessa utmaningar kan påverka noggrannheten och effektiviteten i processen. Förmågan att navigera genom dessa utmaningar blir därmed avgörande för att framgångsrikt implementera automatiserade system för hantering av fakturor. Detta arbete utforskar fyra olika textextraktions metoder som använder optisk teckenigenkänning, bildbehandling, vanlig textextraktion och textbearbetning, följt av en jämförelse mellan de naturliga språkbehandlingsmodellerna GPT- 3.5 (Generative Pre-trained Transformer) och GPT-4 för parameterextraktion av fakturor. Dessa modeller testades på sin förmåga att extrahera åtta specifika fält i PDF-dokument, sedan jämfördes deras resultat. Resultatet presenteras med valideringsmetoden ”Micro F1-poäng” en skala mellan 0 till 1, där 1 är en perfekt extraktion. Metoden som använde GPT-4 visade sig vara mest framgångsrik, som gav ett resultat på 0.98 och felfri extraktion i sex av åtta fält när den testades på 19 PDF-dokument. GPT 3.5 kom på andraplats och visade lovande resultat i fyra av de åtta fält, men presterade inte lika bra i de återstående fält, vilket resulterade i ett Micro F1-poäng på 0.71. På grund av det begränsade datamängden kunde GPT 3.5 inte uppnå sin fulla potential, eftersom finjustering och validering kräver större datamängder. Likaså behöver GPT-4 valideras med ett mer omfattande dataset för att kunna dra slutsatser om modellernas faktiska prestanda. Ytterligare forskning är nödvändig för att fastställa GPT-modellernas kapacitet med dessa förbättringar. / In today’s business environment, many organizations aim to automate the process of extracting information from invoices with the goal of making the management of large volumes of invoices more efficient. However, challenges arise due to the varied structure of invoices. The placement and format of information can significantly differ between different invoices, creating complexity and obstacles in the automated extraction of invoice information. These challenges can impact the accuracy and efficiency of the process, making the ability to navigate through them crucial for the successful implementation of automated systems for invoice management. This work explores four different text extraction methods that use optical character recognition, image processing, plain text extraction, and text processing, followed by a comparison between the natural language processing models GPT-3.5 (Generative Pre-trained Transformer) and GPT-4 for parameter extraction of invoices. These models were tested on their ability to extract eight specific fields in PDF documents, after which their results were compared. The results are presented using the ”Micro F1-Score” validation method, a scale from 0 to 1, where 1 represents perfect extraction. The method that used GPT-4 proved to be the most successful, yielding a result of 0.98 and error-free extraction in six out of eight fields when tested on 19 PDF documents. GPT-3.5 came in second place and showed promising results in four of the eight fields but did not perform as well in the remaining fields, resulting in a Micro F1-Score of 0.71. Due to the limited amount of data, GPT-3.5 could not reach its full potential, as fine-tuning and validation require larger datasets. Similarly, GPT-4 needs validation with a more comprehensive dataset to draw conclusions about the models’ actual performance. Further research is necessary to determine the capacities of GPT models with these improvements.

This dissertation is focused on theoretical and experimental studies of optical properties of materials and multilayer structures composing liquid crystal displays (LCDs) and electrochromic (EC) devices. By applying spectroscopic ellipsometry, we have determined the optical constants of thin films of electrochromic tungsten oxide (WOx) and nickel oxide (NiOy), the films’ thickness and roughness. These films, which were obtained at spattering conditions possess high transmittance that is important for achieving good visibility and high contrast in an EC device. Another application of the general spectroscopic ellipsometry relates to the study of a photo-alignment layer of a mixture of azo-dyes SD-1 and SDA-2. We have found the optical constants of this mixture before and after illuminating it by polarized UV light. The results obtained confirm the diffusion model to explain the formation of the photo-induced order in azo-dye films. We have developed new techniques for fast characterization of twisted nematic LC cells in transmissive and reflective modes. Our techniques are based on the characteristics functions that we have introduced for determination of parameters of non-uniform birefringent media. These characteristic functions are found by simple procedures and can be utilised for simultaneous determination of retardation, its wavelength dispersion, and twist angle, as well as for solving associated optimization problems. Cholesteric LCD that possesses some unique properties, such as bistability and good selective scattering, however, has a disadvantage – relatively high driving voltage (tens of volts). The way we propose to reduce the driving voltage consists of applying a stack of thin (~1µm) LC layers. We have studied the ability of a layer of a surface stabilized ferroelectric liquid crystal coupled with several retardation plates for birefringent color generation. We have demonstrated that in order to accomplish good color characteristics and high brightness of the display, one or two retardation plates are sufficient.

No description available.