<p>In this project it has been focused on the use of a 7.42 um, 4 mW Quantum Cascade Laser in trace gas detection spectroscopy. Norsk Elektro Optikk (NEO) is in possession of a Nanoplus G2102/DFB2/5-12 QCL laser, that can be used in spectroscopic detection of H2O, CO2 and SO2 It has been attempted to construct a setup that can be used for spectroscopic measurements using a self constructed current driver module to produce current pulses for the QCL. The QCL is operated in pulsed mode, with pulses of <500 ns width, and a 1 kHz pulse repetition frequency. Temperature control of the laser has been conducted with a LaserGas II SP monitor module, and temperature has been kept at 280 K during testing. Initially, various test have been conducted to ensure the general functionality of the driver module, and to avoid damage to the QCL. Two different solutions for the transmission line from the driver to the QCL have also been examined, and it has been concluded that the current pulses supplied to the laser are of good quality with minor broadening and short rise/fall times. Furthermore an I-V characteristic for the laser has been produced by incrementing the laser driving current, and measuring the corresponding laser voltage. Measurements of the laser output power have been conducted using a CaF2 collimating lens to focus the laser beam onto a PVI-2TE-8 Vigo photovoltaic detector from Vigo Systems S.A. It has proved difficult to obtain a good signal from the detector, with the maximum voltage measured across a 50Ω shunt resistor being 3 mV. This is 100-200 mV less than what should be expected. Various methods of noise reduction have been applied to improve the detected signal, none have however provided any noticeable improvements. Several possible reasons for the generally low output have been examined.</p>

<p>Optical spectroscopy has been well validated by the physical sciences as a method to characterize chemical compositions in biological material. It has also showed promising to detect atherosclerotic plaques, which can form in the coronary artery walls, and cause heart attacks and strokes. This project seeks to optimize and build fiber optic probes for diffuse reflectance and fluorescence spectroscopy which can assess these plaques. A side-viewing probe is particularly advantageous in the small diameter, confined geometries of arteries. Thus, different techniques are investigated for creating lenses on the tip of optical fibers and design the probes so that they can perform spectroscopic measurements along its circumference. A rigorous testing scheme was developed which included a test matrix and a set of criteria that were used in the optimization process. Two probes for diffuse reflectance and one for fluorescence measurements were built based on the result from the testing scheme. However, a combined probe optimized for both diffuse reflectance and fluorescence measurements could not be created as their respective optimization criteria turned out to be contradictory. The final reflectance probes consisted of two 200 micron fibers separated by 2 mm in the axial direction and the fiber tips were shaped by using a CO2 laser and grinding machine. All the finished probes were tested in a coronary artery of a porcine heart and fat was injected to evaluate their detection of lipid pools. The probes showed good results and were able to detect changes in chromophore content in the tissue and demonstrated the advantages of optimizing a probe for its given application. The fluorescence probe turned out to give good results when used on the arteries from the surface of the heart surface.</p>

<p>The rules of quantum mechanics makes it possible to exchange a secret key at a distance. This is called quantum key distribution (QKD). In theory the key exchange can be made completely secure. Real QKD implementations however, has numerous imperfections. Luckily one has also been able to prove the security of QKD with a large variety of imperfections. The field of QKD has matured over the recent years, and it has now reached commercial applications with photons as the quantum bits, and optical fibers as the quantum channel. Today there are at least three commercial vendors of QKD-systems. We live in the times of quantum hacking. Researchers has begun the task of breaking the security of QKD-systems. Many new imperfections has been discovered, some of which might be used to break the security of QKD. This thesis is a study of the detector efficiency mismatch loophole. Most QKD-systems require two detectors, and it is virtually impossible to make two identical detectors with the exact same efficiency. What is worse, it turns out that the eavesdropper can often control the relative efficiencies of the two detectors trough some domain, for instance by controlling the timing, the frequency or the spacial mode of the photons. This can in turn be used by the eavesdropper to gain information about the secret key. Previously the best known attack would compromise security if the detector efficiency mismatch of about 1:15. Here the current attacks on systems with detector efficiency mismatch are improved to compromise security for a mismatch of about 1:4. This is less than the mismatch found in a commercial QKD-system, so the attack could in principle be used to eavesdrop on this QKD-system. One might try to close the loophole by modifying the implementation. One suggestion is the four state Bob. The problem is that this patch will in turn open other loopholes, and one of these loopholes reopen the detector efficiency mismatch loophole. One can remove Eves information about the key by doing a sufficient amount of extra privacy amplification. Here a general security bound is presented, quantifying the required amount of extra privacy amplification to remove Eve's information about the key. The proof is more general than the previous security proof, and is valid for any basis dependent, possibly lossy, linear optical imperfections in the channel and receiver/detectors. Since this is more realistic assumptions for a QKD-implementation, the proof represents a major step of closing the loophole in real devices.</p>

<p>In this thesis a compact drain current model for nanoscale double-gate MOSFETs is presented. The model covers all operation regimes and bias voltages up to 0.4V. The modeling is done using conformal mapping techniques to solve the 2D Laplace equation in sub-threshold, and using a long channel model in strong-inversion. In near threshold, a quasi-Fermi level model which uses empirical constants is used to find the current. A continuous model is found by expressing asymptotes in the sub-threshold and strong inversion regimes, and combining them using a interpolation function. The interpolation function uses a parameter that is decided analytically from the near threshold calculations. The model shows good agreement with numerical simulations for bias voltages below 0.4V and channel lengths bellow 50nm.</p>

<p>Perfect lenses operating in the near visible spectrum has only recently been introduced, and these kind of metamaterials seem to have a large potential. One problem encountered with these perfect lenses are exceedingly large intrinsic losses, making them impractical for use in applications. This project has explored some of the limitations in using gain to compensate for these losses, specifically the effect of gain saturation has been considered. Gain saturation has been proven to limit the maximum parallel spatial frequency that can be reproduced by the lens. Even though, it has been shown that amplification has the potential to increase the resolution limit by a measurable factor. In the case of several waves traversing the lens simultanously, the critical factor is how much of the total amplitudes lies in waves close to the resolution limit. Waves with relatively small parallel spatial frequencies requires small amplifications, and those with high parallel spatial frequencies will get attenuated or reflected almost immediately, meaning both these types contribute little to gain saturation.</p>

<p>A precise subthreshold potential model for the Quadruple FET (QuadFET) is presented in this thesis. The attempt of modeling the FinFET ("Fin" FET) in the same way failed, but the procedure of the attempt will still be presented in this thesis, and a conclusion of why this modeling did not work is given. For the QuadFET, an analytical solution of the inter-electrode potential distribution of the double-gate MOSFET (DG MOSFET) is used by performing a simple geometric scaling transformation. This is done with a high degree of precision due to structural similarities between the QuadFET and DG MOSFET, accounting for the dierence in gate control of the two devices. A parabolic approximation is then used to model the the cut-plane in the middle of the device, perpendicular to the electron ow from source to drain, of the QuadFET. The resulting analytical solution agrees very well with numerical simulations. For the FinFET, the same analytical solution of the DG MOSFET is used directly in the ground plane of the device, assuming that the electric elds going through the ground plane, into the thick substrate, is negligible. Conformal mapping is then used in the same plane as modeled in the QuadFET, that is the plane in the middle of the device, perpendicular to the electron ow from source to drain, resulting in an analytical solution of the FinFET. Since the potential curvature in the source-drain direction was neglected when making the three dimensional problem of the FinFET to a two dimensional one, the modeling failed. However, an attempt of modeling the transistor has been tested, the electrostatics of the device is better known, and a new way of modeling the device is briey discussed.</p>

<p>Au catalyst ZnO nanostructures have been grown on the a- and c-plane sapphire substrate by PLD. Influence of substrate lattice orientation, substrate surface and different substrate annealing temperature have been characterized by AFM, SEM and XRD. This report shows that a-plane sapphire substrate annealed at 1000 degree C and 1200 degree C improves the growth condition of Au catalyst ZnO nanostructures. For c-plane sapphire; annealing at 1200 degree C and 1400 degree C enhances the nanostructure growth. The better growth condition is a result of the terrace-and-step morphology seen on the substrate surface prior to growth. This report also indicates a correlation between the azimuthal in-plane alignment of the grown nanostructures and the sapphire substrate lattice orientation.</p>

<p>This report presents a method for fabrication of ridge-type waveguide electro-optic modulators in 500 nm thick, c-oriented, epitaxial, (Pb0.92,La0.08)(Zr0.4,Ti0.6)O3 thin films on a MgO substrate. The method is based on ordinary photolitography and wet etching techniques with lift-off metallisation of gold electrodes. To achieve good input coupling of light the device end faces were polished using diamond lapping film swith grain sizes as small as 0.5 um. Several devices with both Mach-Zehnder electro-optic modulators and phase modulators with co-planar gold electrodes and an interaction length of L = 3 mm were fabricated using this method. These modulators were used to examine the electro-optic efect in the thin films at the wavelength 1.55 um. Coherent, linearly polarised light was coupled into the waveguide end face using tapered fibres while a modulation voltage was applied to the electrodes. The phase modulators were used as intensity modulators by exciting them with light polarised 45 degrees on the optical axis and placing a linear polariser at the output. Practical modulation was achieved using voltages as low as 46 V with the phase modulators and 80 V with the Mach-Zehnder modulators. Using a numerical curve fitting technique, the measured data was fitted to a proposed theoretical model for the modulators. The model was based on Jones matrix formalism and the assumption that the electro-optic effect in the thin films corresponds with the Pockels effect. Good fits were achieved indicating that the effect is indeed a Pockels effect and estimates of the Pockels coecient r51 ranged from 4.4 pm/V to 11 pm/V depending on the device. These values were obtained under the uncertain assumption that the birefringence of (Pb,La)(Zr,Ti)O3 is 0.005. It is found that if the actual value of the birefringence is lower, then r51 will also be lower than estimated. Based on previous works the Pockels coeficient was expected to be on the order or ~102 pm/V. The low measured values of r51 and the variation between films is believed to be due to the thin films being multi domain with a domain structure created by a stochastic process.</p>

<p>The major issue with solar cells today, is the price per watt. To tackle this challenge several approaches are being made. One possible approach is to reduce the amount of silicon raw material used in todays wafer-based solar cells by making the wafers thinner. This approach does however bring with it another problem; much of the incident light will escape the cell before being absorbed. One possible way to solve this problem is to use a photonic crystal (PC) as a rear reflector. PCs is a periodic dielectric structure that can reflect light in a non-specular manner, which can substantially increase the optical pathlength for the light within the cell, and hence increase the probability of absorption- One such PC is the inverted opal. To make an inverted opal, one first fabricates a synthetic opal, consisting of microspheres of some kind, that can be used as a template. The gaps between the spheres of such an opal can then be filled with a suitable dielectric, e.g. silicon, and the spheres can be removed by a selective process, leaving the inverted opal structure. In this master project, opals were attempted made with Ugelstad spheres and polysterene (PS) spheres. With the Ugelstad spheres, wafer sized monolayers were made, but opals were not achieved. The PS spheres however, proved very suitable, and opals with a grain size of 150x300$mu m$ were successfully made. These opals were then partially inverted, by first filling in the gaps between the spheres with silicon, using a low temperature low pressure PECVD process, and then heating the samples to 600 degrees Celsius for 2.5 hours.</p>

Optical spectroscopy is a common method used in the determination of quality parameters in groceries. An optical characterization of smoked Atlantic salmon was carried out in this thesis. The optical penetration depth in salmon was found at 531 nm and 632 nm from measurements with lasers as light sources, and from 550 nm to 880 nm with a tungsten halogen lamp as light source. The spectrum of the halogen lamp combined with the absorption spectrum of the salmon made it difficult to obtain results for wavelengths below 550 nm with the halogen lamp. Two variations in the measurements on smoked salmon were performed; measuring on needle insertion versus needle extraction and measuring across several layers of muscle tissue versus measuring along one layer of muscle tissue in salmon. The absorption coefficient and the reduced scattering coefficient of smoked Atlantic salmon was calculated. Significant differences were found dependent on needle insertion or needle extraction, and whether the measurements were made along one layer or across several layers. The penetration depths were found to be 6.79±0.33 mm across several layers and 10.76±1.03 mm along one layer in the measurements with the He-Ne laser. The diffusion approximation was found to be a good approximation for wavelengths from 600 nm to 700 nm. With further development, it may be possible to determine the astaxanthin content of salmon with the method used in this thesis.