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.

The paper and the graphics industries use two instruments with different optical geometry (d/0 and 45/0) to measure the quality of paper prints. The instruments have been reported to yield incompatible measurements and even rank samples differently in some cases, causing communication problems between these sectors of industry.A preliminary investigation concluded that the inter-instrument difference could be significantly influenced by external factors (background, calibration, heterogeneity of the medium). A simple methodology for eliminating these external factors and thereby minimizing the instrument differences has been derived. The measurements showed that, when the external factors are eliminated, and there is no fluorescence or gloss influence, the inter-instrument difference becomes small, depends on the instrument geometry, and varies systematically with the scattering, absorption, and transmittance properties of the sample.A detailed description of the impact of the geometry on the results has been presented regarding a large sample range. Simulations with the radiative transfer model DORT2002 showed that the instruments measurements follow the physical radiative transfer model except in cases of samples with extreme properties. The conclusion is that the physical explanation of the geometrical inter-instrument differences is based on the different degree of light permeation from the two geometries, which eventually results in a different degree of influence from near-surface bulk scattering. It was also shown that the d/0 instrument fulfils the assumptions of a diffuse field of reflected light from the medium only for samples that resemble the perfect diffuser but it yields an anisotropic field of reflected light when there is significant absorption or transmittance. In the latter case, the 45/0 proves to be less anisotropic than the d/0.In the process, the computational performance of the DORT2002 has been significantly improved. After the modification of the DORT2002 in order to include the 45/0 geometry, the Gauss-Newton optimization algorithm for the solution of the inverse problem was qualified as the most appropriate one, after testing different optimization methods for performance, stability and accuracy. Finally, a new homotopic initial-value algorithm for routine tasks (spectral calculations) was introduced, which resulted in a further three-fold speedup of the whole algorithm.The paper and the graphics industries use two instruments with different optical geometry (d/0 and 45/0) to measure the quality of paper prints. The instruments have been reported to yield incompatible measurements and even rank samples differently in some cases, causing communication problems between these sectors of industry.A preliminary investigation concluded that the inter-instrument difference could be significantly influenced by external factors (background, calibration, heterogeneity of the medium). A simple methodology for eliminating these external factors and thereby minimizing the instrument differences has been derived. The measurements showed that, when the external factors are eliminated, and there is no fluorescence or gloss influence, the inter-instrument difference becomes small, depends on the instrument geometry, and varies systematically with the scattering, absorption, and transmittance properties of the sample.A detailed description of the impact of the geometry on the results has been presented regarding a large sample range. Simulations with the radiative transfer model DORT2002 showed that the instruments measurements follow the physical radiative transfer model except in cases of samples with extreme properties. The conclusion is that the physical explanation of the geometrical inter-instrument differences is based on the different degree of light permeation from the two geometries, which eventually results in a different degree of influence from near-surface bulk scattering. It was also shown that the d/0 instrument fulfils the assumptions of a diffuse field of reflected light from the medium only for samples that resemble the perfect diffuser but it yields an anisotropic field of reflected light when there is significant absorption or transmittance. In the latter case, the 45/0 proves to be less anisotropic than the d/0.In the process, the computational performance of the DORT2002 has been significantly improved. After the modification of the DORT2002 in order to include the 45/0 geometry, the Gauss-Newton optimization algorithm for the solution of the inverse problem was qualified as the most appropriate one, after testing different optimization methods for performance, stability and accuracy. Finally, a new homotopic initial-value algorithm for routine tasks (spectral calculations) was introduced, which resulted in a further three-fold speedup of the whole algorithm. / QC 20100707 / PaperOpt, Paper Optics and Colour

Quantum information technology is an emerging field with important applications such as quantum cryptography and teleportation, quantum imaging and lithography. These applications make use of single photons and pairs of entangled photons. In this work, we experimentally generate and attempt to detect the entangled photons. The entangled photon pairs are produced using a nonlinear crystal of beta bariumborate through a process of spontaneous parametric down-conversion (SPDC). Alignment necessary to detect the entangled photon pairs is implemented using a HeNe laser. The experimental results reveal key signatures of the down-converted photons: (i) energy conservation as the wave length of generated photons (810 nm) is two times larger than that of the photons used to optically pump SPDC (405 nm), which is shown by using a 10-nm band-pass filter centred around 810 nm; (ii) the angles between the two photons of a pair correspond to the configuration of momentum conservation calculated analytically;(iii) the photons arrived at the detectors within the jitter time of those; and (iv) orthogonal polarisation of down-converted photons (810 nm) with respect to pump photons (405 nm). These findings show the consequences of SPDC.

An optical frequency comb is a structure of equidistant, coherent spectral components which can be thought of as a large array of individual phase-locked laser sources. Their utilization in precision spectroscopy garnering part of the 2005 Nobel prize, optical frequency combs constitute a relatively novel technology with a large number of potential and actual applications. The research interest grew further with the 2007 discovery of comb structures in microresonators enclosing a nonlinear Kerr medium pumped by an external continuous wave laser, offering both substantially wider combs and the prospect of chip-scale integration. In this thesis work, the modeling of frequency comb spectra generated through optical Kerr cavities is considered using both an Ikeda map and the mean-field Lugiato-Lefever equation to describe the intracavity field evolution. Derivations of these mathematical models are first reviewed alongside relevant physics. They are then treated analytically to constrain model parameters to regions of interest in the context of Kerr-comb dynamics. Finally, numerical parameter sweeps are conducted in both models with respect to the pump power and frequency detuning, where the Ikeda map is additionally examined in the high-energy regime not faithfully described by the Lugiato-Lefever equation. The produced phase diagrams reveal a complex landscape of dynamics including Turing patterns, temporal cavity solitons, breathers and chaos. Ikeda map parameters in the high-energy regime capable of supporting previously reported super energetic cavity solitons are also investigated. Lastly, the numerical simulation package developed for parameter sweeps is presented.

This thesis intends to familiarize the reader with the concepts of photon statistics and correlations in quantum optics. Developing light sources that emit quantum states is central for the realization of quantum technologies. One important step in characterizing these sources is the measurement of field fluctuations and correlations, by coincidence measurements. The expectation value of a coincidence measurement, a simultaneous measurement of two intensities (or, more general, four fields), is represented by the fourth-order correlation function. The value of the correlation function, at zero delay between the detection of two photons, reveals important properties of the state to which they belonged, for example the fluctuations of the photon number. Since predictability is important for many applications, light sources emitting single photons are also characterized by the indistinguishability of consecutively emitted photons, or of two photons from separate emitters. In paper I we investigate blinking behaviour in quantum emitters, and its effect on the interference pattern and photon statistics with photons from two separate emitters. Blinking refers to an emitters transition into a non-emitting state, and subsequent transition back to an emitting state. We show that blinking can not be treated as linear loss, when measuring the fourth-order correlation function for two emitters in a Hong-Ou-Mandel setup. In general, a measurement of the fourth-order correlation function is robust to loss, which makes it a very practical tool. However, the relation between recorded coincidence counts and the correlation function is only direct in the limit of zero detection efficiency, and depends on the detection system. In paper II, we show that by adding a variable attenuation in the beam path, we can trace back to the ''true'' value of the correlation function at zero quantum efficiency. This method improves accuracy in correlation measurements by decreasing a systematic error at the expense of an increased statistical error, which is easier to handle, extending the use of coincidence methods to classical and non-classical multi-photon states. / <p>QC 20180517</p>

The Empirical Valence Bond (EVB) method has long been recognised as a reliable approach for the calculation of free energies of reactions in heterogeneous electrochemical environments. In spite of its established efficacy, existing implementations and protocols often pose challenges due to their tediousness or lack of transparency. This work introduces an open-source Python implementation of the EVB method, specifically designed to enhance accessibility and comprehension of the method making it highly suited for educational purposes. Recommendations are provided for integrating the methodology into the GROMACS application programming interface, to facilitate its integration into computational chemistry workflows and accellerating research. The program is demonstrated through various computations, including a short EVB study on the dissociation of \COt and tetraphenylporphyrin in the vicinity of a graphene sheet in water and dimethylformamide. Moreover, a novel analytical expression for computing the free energy profile is presented, showing promising agreement with the canonical discretised method.

To verify nuclear weapon treaties, such as CTBT the ability to scientifically monitor treaty violations is of importance. One tool for monitoring nuclear weapons testing is the use of gamma ray spectrometry. A calibration on a multi detector element coincidence gamma spectrometer setup was performed from previously gathered experimental data. Data from one calibration sample and a blank sample were analyzed in this project. The first part consisted of energy, full width half maximum (FWHM) and efficiency calibrations, for each of the detectors. Spectra were created, showing the results in the different detectors. From the spectra, several radionuclides were identified, both background nuclides and nuclides from the calibration sample. To each peak, a Gaussian shaped curve was numerically fitted and the parameters were used to perform the calibrations. Efficiencies were calculated for the individual peaks, whereas the energy and FWHM calibrations resulted in linear relationships. During the second part of this project, coincident gamma-rays were investigated. The efficiency for a coincident decay in each detector pair was calculated. This was compared with the product of the singular efficiencies, and a correction term was introduced. Furthermore, the signal to noise ratio was compared for spectra created with different data sorting methods.

No description available.

To investigate near-eld contributions for installed antennas, an in-house code iswritten to incorporate near-eld terms in Shooting and Bouncing Rays (SBR). SBRis a method where rays are launched toward an object and scatter using GeometricalOptics (GO). These rays induce currents on the object, from which the totalscattered eld can be found.To gauge the eect of near-eld terms, the in-house code can be set to excludenear-eld terms. Due to this characteristic, the method is named SBR Includingor Excluding Near-eld Terms (SIENT). The SIENT implementation is thoroughlydescribed. To make SIENT more exible, the code works with triangulated meshesof objects. Antennas are represented as near-eld sources, allowing complex antennasto be represented by simple surface currents. Further, some implementedoptimizations of SIENT are shown.To test the implemented method, SIENT is compared to a reference solution andcomparable commercial SBR solvers. It is shown that SIENT compares well to thecommercial options. Further, it is shown that the inclusion of near-eld terms actsas a small correction to the far-eld of the installed antenna. / För att undersöka närfältsbidrag för installerade antenner, har en kod skrivits för‌att ta med närfältstermer i Shooting Bouncing Rays (SBR). SBR är en metod där strålar (”rays”) skjuts mot ett object och sprids via Geometrisk Optik (GO). Dessa strålar inducerar strömmar på objectet, från vilka det totala sprida fältet kan hittas. För att undersöka bidraget från närfältstermer, så kan koden exkludera dessa. På grund av denna karaktär, kallas koden SBR Including or Excluding Near-field Terms (SIENT). Implementationen av SIENT beskrivs utförligt. För att göra SIENT mer flexibel, arbetar SIENT med triangulerade nät av objekt. Antenner representeras av närfältskällor, vilket låter komplexa antenner representeras med enkla yt-strömmar.Implementerade optimeringar av SIENT visas också.För att testa den implementerade metoden, jämförs SIENT med en referenslösning och jämförbara kommerciella SBR-lösare. Det visas att SIENT överensstämmer bra med kommerciella alternativ. Det visas också att närfältstermer agerar som enmindre korrektion till fjärrfältet av den installerade antennen.

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.