I denne Masteroppgaven ble det dannet filmer av BaSnO på substrat av STO og Nb:STO. Filmene ble grodd i serier der parametrene som ble endret var laserfrekvens, lasereffekt(ved 2Hz og 10Hz)og temperaturen til substratet(ved 2Hz og 10Hz). Tykkelsen til de fleste filmene som ble deponert var mellom 200nm-350nm. For substrattemperaturer mellom 500°C-700°C ble det dannet filmer i hva som sannsynligvis er Ruddlesden Popper serien med en maksimal n kalkulert til å være 169 basert på satellittopper funnet i θ-2θ målinger. For filmer med substrattemperaturer i dette området ble det funnet en lineær sammenheng mellom deponeringsraten i Å per sekund og n i Ruddlesden Popper serien. Det ble funnet at den laveste temperaturen som en krystallinsk film kan bli dannet på minker når laserfrekvensen reduseres. Ved en laserfrekvens på 2Hz ble det dannet krystallinske filmer ned mot substrattemperaturer på 450°C. Ingen filmer ble forsøkt dannet under denne temperaturen og 450°C danner derfor ikke ingen nedre grense for vekst av krystallinske filmer av BaSnO. XPS målinger av filmene i laserfrekvensserien viser et fallende Ba/Sn forhold når høyden på lagene i filmene øker, i samsvar med hva man forventer i Ruddlesden Popper serien. Det ble også foretatt SIMS målinger av 3 filmer i laserfrekvensserien som avslørte at forholdet mellom Ba og Sn er stabilt igjennom hele filmen. SIMS målingene avslørte også Strontium forurensninger i ildematerialet og i filmene. For filmer med substrattemperaturer rundt 780°C ble satellittoppene svakere, muligens på grunn av en overgang fra 2D vekst til 3D vekst. Når laserenergien ved denne temperaturen ble senket ble det dannet filmer av hva som mest sannsynlig er 113 fasen til BaSnO. Det ble foretatt lekkasjestrømmålinger av en film i Ruddlesden Popper serien og lekkasjestrømmer på 1 A/ ble funnet. Det ble også foretatt annealing ved 400°C og 800°C på en av filmene. Dette reduserte intensiteten til satellittoppene i θ-2θ målingene litt da Ruddlesden Popper enhetscellene da går fra å stå ut av planet til å ligge i planet på filmen.

Tynnfilmepitaksi ved pulset laserdeponering av SrRuO3 på TiO2-terminert (001)-orientert SrTiO3-substrat, er i dette arbeidet undersøkt over et stort spekter av deponeringssystemets vekstparametere. Veksten er overvåket ved in situ målinger med elektronstrålediffraksjon (RHEED). Det er vist at tilnærmet perfekt epitaksi er mulig i flere begrensede områder i parameterrommet, der reproduserbarhet hovedsakelig er begrenset av parameterne trykk og temperatur. Resultatene antyder at dette har sammenheng med at kravet til nøyaktig reprodusering av ablasjonsforhold vil variere avhengig av hvor, i spekteret av trykk og temperatur, veksten foregår. Arbeidet omfatter også en undersøkelse av instrumentering. Optimalisering av temperaturmålinger med pyrometer, limeprosedyre og innstilling av laserenergitetthet på target er gjort. Resultater fra denne undersøkelsen viser at deponeringstemperaturen er reproduserbar med ±13 °C og at laserenergi-tettheten på target er usikker. En rekke tiltak som kan minimere usikkerheten i laserenergitettheten er gjennomgått.

Cryptography has begun its journey into the field of quantum information theory. Classical cryptography has shown weaknesses, which may be exploited in the future, either by development in mathematics, or by quantum computers. Quantum key distribution (QKD) is a promising path for cryptography to enable secure communication in the future. Although the theory of QKD promises absolute security, the reality is that current quantum crypto systems have flaws in them, as perfect devices have proven impossible to build. However, this can be taken into account in security proofs to ensure security, even with flaws. Security loopholes in QKD systems are being discovered as development progresses. Nevertheless, the system being built at NTNU is intended to address them all, creating a totally secure system. During this thesis, work was continued assembling the interferometer which is the basis for encoding qubits. It was fully connected on an optical table, and interference was obtained. Concerning theoretical work, calculations for a photon source specific parameter was carried out. It consisted of expanding previous framework and applying the results in both an established security proof, and a recent generalization of this proof. Two source effects were in focus, the lasers random phase and its fluctuating pulse intensity. Where analytical derivation was no longer possible, Matlab was used for numerical calculations. Under the conditions of the framework and proofs this thesis lies on, randomized phase turned out to have a negligible improvement over the case of non-random phase. Fluctuating amplitude showed a larger effect, reducing system performance. The input parameters were extreme, thus in a realistic situation it should not affect system performance significantly. However, these fluctuations must be taken into account when proving system security.

Modelling of multimode and layer structure by transfermatrices

Støyreduksjon har blitt utført på hyperspektrale bilder i både spektral retning og romlige retninger. Algoritmene som har blitt benyttet for å oppnå støyreduksjon er Principal Component Analysis (PCA), Maximum Noise Fraction (MNF) og wavelet-transform. MNF-algoritmen har blitt kjørt med mange forskjellige støyestimatorer for å bestemme hvilke av disse som gir høye signal-støy-forhold. Å utføre støyestimatet i fourierrommet har også blitt undersøkt. Dette ga gode resultater når man benyttet fasedifferansen med nærliggende piksler som estimator for hyperspektrale bilder tatt under hvitt lys. Ble derimot kilden endret til en 355nm laserkilde fikk man langt dårligere resultater. Det er bare Haar-transformen som har blitt brukt til wavelet-transformasjon. Haar-transformen ga dårlig støydempning i både spektral retning og romlige retninger. Algoritmene PCA og MNF fungerer bra til støyreduksjon. I spektral retning er det liten forskjell mellom PCA og de ulike støyestimatene som er brukt under MNF. Ser man derimot på det romlige planet finner en større forskjeller mellom dem. Dette gjelder spesielt for spektralbånd med lav intensitet og mye støy. Her gir PCA bedre støydempning enn MNF. Støyreduksjonen ved PCA og MNF kommer som en direkte følge av å begrense antallet prinsipalkomponenter under tilbaketransformasjonen. Hvor grensen bør settes for hvilke prinsipalkomponenter som skal bevares, ble også vurdert. Når lyskildeforholdene for de hyperspektrale bildene blir sammenlignet er grensen valgt slik at 99,25% av det opprinnelige signalet blir bevart. Spekteret til hyperspektrale bilder tatt under hvitt lys har høy intensitet for lange bølgelengder, og lav intensitet ved korte bølgelengder. Endres derimot lyskilden til en 355nm laserkilde får man lav intensitet for lange bølgelengder og høy intensitet for korte.

The increase in the world’s demand for energy, and the fact that at one point we will run out of oil and gas which are two major contributers of the world supply of energy toady, are two reasons for why new and reliable energy sources are needed. The solar industry is one of the fastest growing industires, but the price of energy delivered by solar cells is still too high compared to other alternatives. More research is therefore needed in order to drive the price of solar energy down.In this report seven silicon nitride films with different stoichiometry are deposited on silicon substrate by the plasma enhanced chemical vapor de- position (PECVD) method. The deposition conditions are selected in order to enhance the formation of silicon nanoclusters. Silicon nanostructures have interesting properties due quantum effects observed at these dimensions. The most interesting of these properties is the ability to tune the silicon nanos- tructures to absrob ligth at different wavelengths. High energy light cannot be utilized in silicon solar cells. With the application of silicon nanostruc- tures, this light can be absorbed and down-converted to usable light which is then transmitted into the solar cell. This would increase the efficiency of the soalr cell, which results in cheaper energy. Two ensembles of as-deposited and annealed (annealed at 1050◦ C) samples were characterized with dif- ferent techniques in order to find the thickness, composition, light emitting sources and optical constants of the films. The techniques used were ellipsom- etry, photo-luminescence (PL) and transmission electron microscopy (TEM).The results obtained shows that all films are porous (indicated by the low index of refraction). One of the effects of annealing is an increase in the refractive index for all samples, which is an indication that the films have become more compact as a result of the annealing process. PL is obtained for samples with a high flow of ammonia, while samples of a low flow have little or no PL. The annealing process increase the PL observed for samples with a high ammonia flow, while a reduction is observed for the samples with a low flow. TEM images reveals that only one sample has any nanostructures present, so the observed PL is likely related to defect states.

A literature review of relevant luminescence spectra for silicon solar cell materials has been performed. Three multi crystalline silicon samples in particular has been the focus of attention, one electronic grade sample R6, and two solar grade samples ES1, and MH2, where MH2 has added chromium. A list of relevant luminescence spectra has been compiled, and can be found in the appendix.The samples was measured using low temperature micro photoluminescence. They where cooled down by liquid helium in a cryostat, and excited using a laser. Photoluminescence was captured by a camera mounted on a spectrometer. Noise components was measured and removed, but are subject to changes in between measurements, causing some unwanted artifacts to appear in the end result.Luminescence due to P and B doping atoms are identified in ES1, and MH2 as expected, and a weak boron bound exciton line is also present in the clean sample R6. R6 also show signs of having a carbon-carbon complex impurity forming at grain boundaries. Lines attributed to chromium boron pairs where not observed in MH2, presumably due to the lack of such pairs. ES1 exhibits a luminescence attributed to a higher quality material, than both MH2, and R6. Expected behavior is for R6 to have such traits, but this is not the case. The reason for ES1 to show this enhanced luminescence is not known. Lines attributed to dislocations are observed in all the samples, but consist of less intense peaks than expected.Local heating is a severe problem using micro photoluminescence. Bound excitons, impurity lines, and dislocation related lines, all loose intensity at higher temperatures. The intrinsic TO line also have a substantial broadening with respect to energies, suggesting that local temperatures are as much as 70K higher than the sample holder temperature, when exciting with 128 mW using a 2 µm spot diameter.

Over the recent years semiconductor nanowires have gained much attention for their potential to either improve existing technology or create novel devices. This potential has been realized in devices such as semiconductor nanowire lasers[2-3] and nanowire single-photon detectors[4]. With nanowire technology it could be possible to create single-photon nanowire lasers that emit photons in the near infrared region. Such devices should prove very interesting for telecommunications and quantum cryptography.The purpose of this master thesis was the study of the optical properties of GaAs nanowires with GaAsSb inserts. For this reason, both nanowires with and without an AlGaAs coating to increase the nanowire Quantum Efficiency (QE) have been subjected to low temperature PL spectroscopy. In an attempt to determine the physical origin of the different optical properties of different nanowires, µ-PL spectroscopy, Scanning Transmission Electron Microscopy (STEM) and Transmission Electron Microscopy (TEM) was carried out on the same nanowires of a sample with AlGaAs shell nanowires. Through these measurements, it was found that STEM at 30 kV did not change the optical properties of the nanowire, but 200 kV TEM had a detrimental effect on nanowire PL. Through the structurally and optically correlated examination, it was found that stacking faults near the insert was not the origin of the power dependent behavior of the insert emission, and in combination with PL measurements of both zincblende (ZB) and wurtzite (WZ) GaAs nanowires the electronic band structure of the nanowire inserts was determined to very likely be type-II. Also, a theoretical explanation of the origin of the observed insert emission behavior was presented, and polarization dependent PL measurements were presented and discussed.

A prototype of a fiber based absorptionspectroscopy instrument is built. A single mode fiber pigtailDistributed Feedback laser (DFB) is used to scan a known$mbox{NH}_3$ absorption line near $1512nm$ ($6614cm^{-1}$). $2mm$diameter InGaAs PIN photodiodes are used to convert the light signalto electrical signals by use of special designed transimpedanceamplifiers. Laser modulation, coherent detection at twice themodulation frequency (second harmonic detection), other electronics,and digital signal processing are provided by Norsk Elektrooptikk.bigskip The DFB laser from NEL (NLK1S5EAAA) delivers 10mW fiberoutput and has maximum output around 30mW at maximum injectioncurrent of 200mA. This laser was found to be very quiet at dcoperation. However, in wavelength modulation spectroscopy operationit exhibit large modulation noise that was found to stem from thefiber coupling inside the laser module. A detection limit of$6times10^{-5}$ to $1times10^{-4}$ in absorbance unit with 0.712moptical path length and an effective measurement bandwidth of 52Hzwas achieved by this laser. This is significantly above thedetection limit with free air lasers which achieve $3times10^{-6}$relative absorbance (0.15ppm $mbox{NH}_3$ at room temperature andatmospheric pressure). The acquisition time for each concentrationmeasurement takes 3.2s. Hence, the response time is very fast whichis a common property of wavelength modulation spectroscopy.bigskip The modulation noise problem was attacked by an electronicnoise cancellation scheme. The idea was that since the noise sourceis inside the laser module and no external optical component can beused to reduce it. With great linearity and reliability propertiesof fused biconical taper (FBT) couplers the laser beam is split intotwo identical beams with nearly equal amount of the same noise. Onebeam, signal beam, is used to induce second harmonic signals in thegaseous path. The other beam goes directly to an identicalphotodetector and is used as a reference signal. Two specialdesigned noise canceller circuits were built to remove commonsignals. Both the circuits, based on current subtraction (notoptimized) or voltage subtraction, give comparable results. Themodulation noise was reduced by more than 12dB. A detection limit of$5times10^{-6}$ was achieved with this prototype. Even aftertransmitting the laser beam through a 3200 meter single mode fiber asignal to noise ratio (relative to 100ppm signal) of $180times$.Hence, a sensitivity is $1.1times10^{-5}$ in absorbance unit wasachieved with the basic noise canceller (not optimized). Thiscorresponds to a detection limit of 0.55ppm ammonia (12.5ppm withoutcancellation). The optimized noise canceller could reduce this by afactor of 3 or more.bigskipThe basic noise canceller based on current domain subtraction wasinvestigated in detail and optimized. This new circuit suppressedthe intensity modulation signal by more than 70dB. The 2f noise wasreduced to approximately 50ppb or $1.1times10^{-6}$ in absorbanceunit with an effective noise bandwidth of 52.3Hz and 1m optical pathlength. This is a record sensitivity with such simple electronics.The sensitivity of our fiber based prototype is limited by thefluctuating etalon fringing in the signal beam. Under normaloperation the prototype achieves approximately $pm20$ppb zero pointdrift in the concentration with an acquisition time of 48s (3.5Hznoise bandwidth). By our knowledge these results are the bestavailable and are competitive with the much more complex frequencymodulation spectroscopy technique.bigskipThese balanced transimpedance amplifiers also have the ability tomeasure the absorption spectra directly without modulation.Determining the absorption linewidth and its shape is now a straightforward task. By use of dual beam configuration and noisecancellation thermal effects that caused background fluctuationswere greatly suppressed. The laser delivers high intensity light,$sim22mW$. The dominating noise is the photocurrent shot noise andthe etalon fringing from optical components in the signal path.Remote sensing, in-situ, noninvasive measurements can be performedwith this instrument. In some cases it's flexibility, and remotesensing possibility are of great attractiveness for the industry.The sensitivity is also improved by a factor of two with the fiberbased tuneable diode laser absorption spectroscopy instrument.bigskipIn the end of this thesis we demonstrate the ability to measuremultiple absorption lines simultaneously. The number of measurementpaths is limited by the laser output power.

This thesis covers the basics of cryptography, both classical and the newer quantum-basedapproches. Further, it details an implementation of a BB84-based quantum key distributionsystem currently under construction, focusing on the controlling hardware and FPGA-basedsoftware. The overarching goal is to create a system impervious to currently known attackson such systems. The system is currently running at 100 Mbit/s, though the goal is to double this asthe design nears its completion. The system currently chooses encoding base, bit value andwhether a state is a socalled decoy state. However, the modulator for bit encoding is notyet operational. Output for decoy state generation, however, is fully functional. Finally, the thesis describes what steps are necessary to reach a complete BB84-basedquantum key distribution system implementing decoy states.