<p>It is very interesting to probe the rotational symmetry of semiconductor quantum dots for quantum information and quantum computation applications. We studied the effects of rotational symmetry in semiconductor quantum dots using configuration interaction calculation. Moreover, to compare with the experimental data, we studied the effects of hidden symmetry. The 2D single-band model and the 3D single-band model were used to generate the single-particle states. How the spectra affected by the breaking of hidden symmetry and rotational symmetry are discussed. The breaking of hidden symmetry splits the degeneracy of electron-hole single-triplet and triplet-singlet states, which can be clearly seen from the spectra.</p><p>The breaking of rotational symmetry redistributes the weight percentage, due to the splitting of p_x and p_y states, and gives a small brightness to the dark transition, giving rise to asymmetry peaks. The asymmetry peaks of 4X, 5X, and 6X were analyzed numerically. In addition, Auger-like satellites of biexciton recombination were found in the calculation. There is an asymmetry peak of the biexciton Auger-like satellite for the 2D single-band model while no such asymmetry peak occurs for the 3D single-band model. Few-particle effects are needed in order to determine the energy separation of the biexciton main peak and the Auger-like satellite.</p><p>From the experiments, it was confirmed that the lower emission energy peak of X^2- spectrum is split. The competed splitting of the X^2- spectra were revealed when temperature dependence was implemented. However, since the splitting is small, we suggest the X^2- peaks are broadened in comparison with other configurations according to single-band models. Furthermore, the calculated excitonic emission patterns were compared with experiments. The 2D single-band model fails to give the correct energy order of the peaks for the few-particle spectra; on the other hand the peaks order from 3D single-band model consistent with experimental data.</p>

<p>Photonic crystals are periodic structures that offers the possibility to control the propagation of light.</p><p>The revised plane wave method has been implemented in order to compute band structures for photonic crystals. The main advantage of the revised plane wave method is that it can handle lossless dispersive materials. This can not be done with a conventional plane wave method. The computational challenge is comparable to the conventional plane wave method.</p><p>Band structures have been calculated for a square lattice of cylinders with different parameters. Both dispersive and non-dispersive materials have been studied as well as the influence of a surface roughness.</p><p>A small surface roughness does not affect the band structure, whereas larger inhomogeneities affect the higher bands by lowering their frequencies.</p>

<p>Denna rapport behandlar en energiundersökning av värmekablar på uppdrag av INEOS ChlorVinyls anläggning i Stenungsund. Eftersom miljön får en större och större betydelse i dagens samhälle försöker alla sektorer i samhället minska sin energiförbrukning. År 2006 använde svensk industri 157 TWh energi och 35,8 % av detta var elenergi. Den kemiska industrin står för 8 % (2006) av Sveriges industriers energiförbrukning och räknas som en energiintensiv bransch. Fabriken i Stenungsund har länge haft ett mycket förmånligt elavtal vilket har gjort att de inte har varit lönsamt att bry sig om att göra relativt småskaliga effektiviseringar. Men nu med ökade energipriser är det aktuellt att titta på vad som kan göras och till vilket pris. Syftet med utredningen är att undersöka om ett annorlunda upplägg av termostaterna som styr värmekablarna gör att man kan spara energi genom att värmen bara ligger på när det verkligen behövs. Genom undersökning och jämförelse av olika termostater koms det fram till att det inte finns noggrannare termostater på marknaden än de som sitter i fabriken. Termostaten till VKB14 är dock felvald. Med hjälp av temperaturstatistik och ett medelvärde av antal timmar under en viss temperatur över de två vintersäsongerna har effektåtgången för VKA14 och VKB14 räknats ut. Genom mätningen av när kontaktorn slår till i VKB14 har det utlästs att detta skåp ligger till 38 % av tiden när temperaturen i intervallet är så hög att det inte borde vara till alls. Om man utgår från att skåpet gör av med 20 000 W när det är igång i onödan, ger detta att det förbrukar 1,3 gånger mer energi per år än vad som behövs vid en temperaturinställning på +5°C.</p>

<p>Det här examensarbetets syfte är att skapa en inspelningsstudio åt Strömkullegymnasiet i Bengtsfors. Det innefattar både akustik och teknik då båda delar är viktiga för resultatet av en inspelning. Elever och lärare på andra musikgymnasier har berättat hur studion fungerar på deras skolor och deras erfarenheter har varit till hjälp i det här arbetet. Den största utmaningen med projektet är att det inte finns någon lokal att bygga en studio i utan ett koncept som är flyttbart utan att man behöver påverka den gamla eller den nya lokalen måste utformas.</p><p>Projektet kunde inte slutföras då det inte är bestämt var studion ska placeras. Det har tillkommit alternativa lokaler som skiljer sig drastiskt från de två ursprungliga alternativen.</p> / <p>The purpose of this degree work is to help Strömkullegymnasiet in Bengtsfors to get a recording studio. It involves both the acoustics and the equipment because both parts are important to the outcome of a recording. Teachers and students from other music high schools have told how their studios works and their experience have been a good help for this report. The biggest challenge with this project is that it doesn’t exist a location where a studio can be built so a new moveable studio concept has to be developt that does not affect the new location.</p><p>The project couldn’t be completed because the decision where to locate the studio has not been taken. Some other locations is under investigation and they are a lot different from the original locations.</p>

In this thesis, noise coupling simulation is introduced into the behavioral level. Methods and models for simulating on-chip noise coupling at a behavioral level in a design flow are presented and verified for accuracy and validity. Today, designs of electronic systems are becoming denser and more and more mixed-signal systems such as System-on-Chip (SoC) are being devised. This raises problems when the electronics components start to interfere with each other. Often, digital components disturb analog components, introducing noise into the system causing degradation of the performance or even introducing errors into the functionality of the system. Today, these effects can only be simulated at a very late stage in the design process, causing large design iterations and increased costs if the designers are required to return and make alterations, which may have occurred at a very early stage in the process. This is why the focus of this work is centered on extracting noise coupling simulation models that can be used at a very early design stage such as the behavioral level and then follow the design through the various design stages. To realize this, SystemC is selected as a platform and implementation example for the behavioral level models. SystemC supports design refinement, which means that when designs are being refined and are crossing the design levels, the noise coupling models can also be refined to suit the current design. This new way of thinking in primarily mixed-signal designs is called Behavioral level Noise Coupling (BeNoC) simulation and shows great promise in enabling a reduction in the costs of design iterations due to component cross-talk and simplifies the work for mixed-signal system designers. / Electronics Design Division

Optical fibre sensors can be used to measure a wide variety of properties. In some cases they have replaced conventional electronic sensors due to their possibility of performing measurements in environments suffering from electromagnetic disturbance, or in harsh environments where electronics cannot survive. In other cases they have had less success mainly due to the higher cost involved in fibre-optic sensor systems. Intensity modulated fibre-optic sensors normally require only low-cost monitoring systems principally based on light emitting diodes and photo diodes. The sensor principle itself is very simple when based on coupling between fibres, and coupling based intensity modulated sensors have found applications over a long time, mainly within position and vibration sensing. In this thesis new concepts and applications for intensity modulated fibre-optic sensors based on coupling between fibres are presented. From a low-cost and standard component perspective alternative designs are proposed and analyzed in order to find improved performance. The development of a sensor for an industrial temperature sensing application, involving aspects on multiplexing and fibre network installation, is presented. Optical time domain reflectometry (OTDR) is suggested as an efficient technique for multiplexing several coupling based sensors, and sensor network installation with blown fibre in micro ducts is proposed as a flexible and cost-efficient alternative to traditional cabling. A new sensor configuration using a fibre to a multicore fibre coupling and an image sensor readout system is proposed. With this system a high-performance sensor setup with a large measurement range can be realised without the need for precise fibre alignment often needed in coupling based sensors involving fibres with small cores. The system performance is analyzed theoretically with complete system simulations on different setups. An experimental setup is made based on standard fibre and image acquisition components, and differences from the theoretical performance are analyzed. It is shown that sub-µm accuracy should be possible to obtain, being the theoretical limit, and it is further suggested that the experimental performance is mainly related to two error sources: core position instability and differences between the real and the expected optical power distribution. Methods to minimize the experimental error are proposed and evaluated.

It is very interesting to probe the rotational symmetry of semiconductor quantum dots for quantum information and quantum computation applications. We studied the effects of rotational symmetry in semiconductor quantum dots using configuration interaction calculation. Moreover, to compare with the experimental data, we studied the effects of hidden symmetry. The 2D single-band model and the 3D single-band model were used to generate the single-particle states. How the spectra affected by the breaking of hidden symmetry and rotational symmetry are discussed. The breaking of hidden symmetry splits the degeneracy of electron-hole single-triplet and triplet-singlet states, which can be clearly seen from the spectra. The breaking of rotational symmetry redistributes the weight percentage, due to the splitting of px and py states, and gives a small brightness to the dark transition, giving rise to asymmetry peaks. The asymmetry peaks of 4X, 5X, and 6X were analyzed numerically. In addition, Auger-like satellites of biexciton recombination were found in the calculation. There is an asymmetry peak of the biexciton Auger-like satellite for the 2D single-band model while no such asymmetry peak occurs for the 3D single-band model. Few-particle effects are needed in order to determine the energy separation of the biexciton main peak and the Auger-like satellite. From the experiments, it was confirmed that the lower emission energy peak of X2- spectrum is split. The competed splitting of the X2- spectra were revealed when temperature dependence was implemented. However, since the splitting is small, we suggest the X2- peaks are broadened in comparison with other configurations according to single-band models. Furthermore, the calculated excitonic emission patterns were compared with experiments. The 2D single-band model fails to give the correct energy order of the peaks for the few-particle spectra; on the other hand the peaks order from 3D single-band model consistent with experimental data.

Photonics nowadays is one of the most rapidly developing areas of modern physics. Photonic chips are considered to be promising candidates for a new generation of high-performance systems for informational technology, as the photonic devices provide much higher information capacity in comparison to conventional electronics. They also offer the possibility of integration with electronic components to provide increased functionality. Photonics has also found numerous applications in various fields including signal processing, computing, sensing, printing, and others. Photonics, which traditionally covers lasing cavities, waveguides, and photonic crystals, is now expanding to new research directions such as plasmonics and nanophotonics. Plasmonic structures, namely nanoparticles, metallic and dielectric waveguides and gratings, possess unprecedented potential to guide and manipulate light at nanoscale. This Thesis presents the results of theoretical studies of light propagation in photonic and plasmonic structures, namely lasing disk microcavities, photonic crystals, metallic gratings and nanoparticle arrays. A special emphasis has been made on development of high-performance techniques for studies of photonic devices. The following papers are included: In the first two papers (Paper I and Paper II) we developed a novel scattering matrix technique for calculation of resonant states in 2D disk microcavities with the imperfect surface or/and inhomogeneous refraction index. The results demonstrate that the surface imperfections represent the crucial factor determining the $Q$ factor of the cavity. A generalization of the scattering-matrix technique to the quantum-mecha\-nical electron scattering has been made in Paper III. This has allowed us to treat a realistic potential of quantum-corrals (which can be considered as nanoscale analogues of optical cavities) and has provided a new insight and interpretation of the experimental observations. Papers IV and V present a novel effective Green's function technique for studying light propagation in photonic crystals. Using this technique we have analyzed surface modes and proposed several novel surface-state-based devices for lasing/sensing, waveguiding and light feeding applications. In Paper VI the propagation of light in nanorod arrays has been studied. We have demonstrated that the simple Maxwell Garnett effective-medium theory cannot properly describe the coupling and clustering effects of nanorods. We have demonstrated the possibility of using nanorod arrays as high-quality polarizers. In Paper VII we modeled the plasmon-enhanced absorption in polymeric solar cells. In order to excite a plasmon we utilized a grated aluminum substrate. The increased absorption has been verified experimentally and good agreement with our theoretical data has been achieved.

Quantum mechanics is basically a mathematical recipe on how to construct physical models. Historically its origin and main domain of application has been in the microscopic regime, although it strictly seen constitutes a general mathematical framework not limited to this regime. Since it is a statistical theory, the meaning and role of probabilities in it need to be defined and understood in order to gain an understanding of the predictions and validity of quantum mechanics. The interpretational problems of quantum mechanics are also connected with the interpretation of the concept of probability. In this thesis the use of probability theory as extended logic, in particular in the way it was presented by E. T. Jaynes, will be central. With this interpretation of probabilities they become a subjective notion, always dependent on one's state of knowledge or the context in which they are assigned, which has consequences on how things are to be viewed, understood and tackled in quantum mechanics. For instance, the statistical operator or density operator, is usually defined in terms of probabilities and therefore also needs to be updated when the probabilities are updated by acquisition of additional data. Furthermore, it is a context dependent notion, meaning, e.g., that two observers will in general assign different statistical operators to the same phenomenon, which is demonstrated in the papers of the thesis. It is also presented an alternative and conceptually clear approach to the problematic notion of "probabilities of probabilities", which is related to such things as probability distributions on statistical operators. In connection to this, we consider concrete numerical applications of Bayesian quantum state assignment methods to a three-level quantum system, where prior knowledge and various kinds of measurement data are encoded into a statistical operator, which can then be used for deriving probabilities of other measurements. The thesis also offers examples of an alternative quantum state assignment technique, using maximum entropy methods, which in some cases are compared with the Bayesian quantum state assignment methods. Finally, the interesting and important problem whether the statistical operator, or more generally quantum mechanics, gives a complete description of "objective physical reality" is considered. A related concern is here the possibility of finding a "local hidden-variable theory" underlying the quantum mechanical description. There have been attempts to prove that such a theory cannot be constructed, where the most well-known impossibility proof claiming to show this was given by J. S. Bell. In connection to this, the thesis presents an idea for an interpretation or alternative approach to quantum mechanics based on the concept of space-time. / QC 20100810

The research work presented in this thesis deals with modelling, design and characterisation of passive and active optical waveguide devices. The rst part of the thesis is related to algorithm development and numerical modelling of planar optical waveguides and gratings using the Method of Lines (MoL). The basic three-point central-di erence approximation of the δ2=δx2 operator used in the Helmholtz equation is extended to a new ve-point and seven-point approximation with appropriate interface conditions for the TE and TM elds. Di erent structures such as a high-contrast waveguide and a TM surface plasmon mode waveguide are simulated, and improved numerical accuracy for calculating the optical mode and propagation constant is demonstrated. A new fast and stable non-paraxial bi-directional beam propagation method, called Cascading and Doubling algorithm, is derived to model deep gratings with many periods. This algorithm is applied to model a quasi-guided multi-layer anti-resonant reecting optical waveguide (ARROW) grating polarizing structure. In the second part of the thesis, our focus is on active optical devices such as vertical-cavity and edge-emitting lasers. With a view to improve the bandwidth of directly modulated laser, an InGaAsP quantum well with InGaAlAs barrier is studied due to its favorable band o set for hole injection as well as for electron con nement. Quantum wells with di erent barrier bandgap are grown and direct carrier transport measurements are done using time and wavelength resolved photoluminescence upconversion. Semi-insulating regrown Fabry-Perot lasers are manufactured and experimentally evaluated for light-current, optical gain, chirp and small-signal performance. It is shown that the lasers having MQW with shallow bandgap InGaAlAs barrier have improved carrier transport properties, better T0, higher di erential gain and lower chirp. For lateral current injection laser scheme, it is shown that a narrow mesa is important for gain uniformity across the active region. High speed directly modulated DBR lasers are evaluated for analog performance and a record high spurious free dynamic range of 103 dB Hz2=3 for frequencies in the range of 1-19 GHz is demonstrated. Large signal transmission experiment is performed at 40 Gb/s and error free transmission for back-to-back and through 1 km standard single mode ber is achieved. / QC 20100827