<p>This project was worked on during the autumn 2005 at the Norwegian University of Science and Technology, Department of Electronics and Telecommunications. The assignment was to write a new LabVIEW programme that is to run the measurement procedure of a laser probe setup. The setup is used in characterization of surface acoustic waves(SAW). A programme was written that contained the necessary functionality and proved to operate satisfactorily. Several measurements were made on a SAW transducer, accurately picturing the wave. Fourier analysis were performed on the collected data in order to separate the propagation directions. An absolute amplitude measurement was made on a heterodyne interferometer, and the result was compared to a similar scan made using the laser probe. The work shows that the setup is ready for calibration against the heterodyne interferometer, in order to enable the laser probe to measure absolute amplitude by itself.</p>

<p>Study of the Polarization Dependent Loss caused by the combined effect of orthogonality degradation and dynamic power fluctuations in a hybrid network, which combines circuit switching with packet switching to transmit applications with very different quality requirements on the same wavelength channel.</p>

<p>In this assignment the theoretical background for the nature of speckle is presented and practical work was done to reduce the speckle effect in a display system based on a laser source. This was done without any picture modulators, or any kind of line scan or flying spot scanning. Work was done to find the right setup to be able to as easy as possible characterize the statistics of the speckle in an image. A still image of an expanded laser spot worked as an image. A series of test sets were carried out to address the different factors which could make a difference on the speckle contrast and their role in such systems.</p>

<p>Polarization Effects in Wavelength Converters based on Semiconductor Optical Amplifiers</p>

<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>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>