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Thesis (Ph.D.)--Montana State University--Bozeman, 2007. / Typescript. Chairperson, Graduate Committee: John L. Carlsten. Includes bibliographical references.

Resonant cavity controlled klystron frequency stabilization circuits and quartz-crystal oscillator frequency stabilization circuits were investigated for reflex klystrons operating at frequencies in the X-band range. The crystal oscillator circuit employed achieved better than 2 parts in 10 in frequency stability. A test of the functional properties of the frequency standard was made using the Stark effect in molecules.

The thesis presents design, development and realization of laser system with stabilized optical frequency which could become the basis of an etalon of wavelength for the telecommunication band of the near-infrared spectral region. Semiconductor DFB laser diode is used as a tunable source of radiation with narrow linewidth. Its optimum operation is ensured by especially designed current and temperature controller. The laser is prestabilized using FM spectroscopy technique to the passive Fabry-Perot cavity. This fast feed-back loop is able to improve spectral characteristics of the laser. The center frequency of the F.-P. cavity - the laser optical frequency is locked by a slow second feed-back loop to the absorption spectral line of acetylene 13C2H2 gas. The slow control loop is based on the third derivative spectroscopy technique. Relative stability at the level of 10E-12 was achieved.

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<p>In this Thesis I report on my work done in replicating the Pound-Drever-Hall (PDH) laser stabilization technique as well as applications of PDH to microring resonators and generated Optical Frequency Combs (OFC). These works have been broken down into three sections. First, I replicated the PDH method with a continuous wave (CW) laser along with a Fabry-Pérot Cavity (FPC). Second, I applied the same technique to a 25 GHz Free Spectral Range (FSR) microring resonator fabricated in Silicon Nitride. Third, I applied the PDH technique to a high Quality Factor (Q) high Free Spectral Range (FSR) microring resonator in preparation to lock the repetition rate of two soliton combs beat together. The last experiment was for an application towards a compact optical clock system; such systems will have a wide impact on the infrastructure of our navigation and communication structures in use today.</p>

A new fully integrated wavelength stabilization scheme based on grating-coupled surface-emitting lasers is explored. This wavelength stabilization scheme relies on two gratings. The first grating is fabricated on the p-side of the semiconductor laser in close proximity to the laser waveguide such that it couples light out of the guided mode of the waveguide into a propagating mode in the substrate; this grating is known as the grating coupler. The second grating is fabricated on the n-side of the substrate such that for the stabilization wavelength, this second grating operates in the Littrow condition and is known as the feedback grating. Furthermore with the proper design of the two gratings, the feedback grating will operate under total internal reflection conditions allowing a near unity retro-reflection of the light of the stabilization wavelength. The grating coupler and feedback grating together comprise a dual grating reflector (DGR). The DGR wavelength stabilization scheme is investigated both theoretically by means of numerical modeling and experimentally by integration of a DGR as a wavelength selective reflector into a single quantum well semiconductor laser with a gain peak centered at 975nm. Numerical modeling predicts a peak reflection of approximately 70% including losses and a spectral width of 0.3nm. The integration of a DGR into a semiconductor laser proved both the efficacy of the scheme and also allowed us to experimentally determine the effective reflectivity to be on the order of 62%; the spectral width of light output from these devices is typically on the order of 0.2nm. Furthermore, these devices had light-current characteristic slopes greater than 0.84W/A operating under continuous wave conditions. The DGR was then modified to provide a reflection with two spectral peaks. A semiconductor device incorporating this dual wavelength DGR was fabricated and tested. These devices showed a peak optical power of in excess of 5.5W and a light-current characteristic slope of 0.86W/A in quasi continuous wave operation; these devices also exhibit a large operating current range in which both wavelengths have comparable output powers. Another modified DGR design was investigated for the purpose of providing an even narrower spectral reflection. Devices incorporating this modified design provided an output with a spectral width as narrow as 0.06nm. DGRs were also integrated into an extremely broad area device of an unorthodox geometry; square devices that lase in two orthogonal directions were fabricated and tested. The last idea investigated was combining a DGR wavelength stabilized laser with a tapered semiconductor optical amplifier into a master oscillator power amplifier device, with the optical coupling between the two components provided by identical grating couplers disposed on the p-side surfaces of each of the devices. These master oscillator power amplifiers provide a peak power of 32W when operating under quasi continuous wave operation.

Master of Science / Department of Electrical and Computer Engineering / Dwight D. Day / Micro-hydro turbines generate power for small villages and industries in Afghanistan. They usually produce less than 100 kW of power. Currently the flow into the turbine is controlled manually and the voltage is controlled automatically with an electronic load controller. Excess power not used by the village is dumped into a community water heater. For larger sites that have a reservoir and/or large variable load throughout the day and night, the turbine needs to be fitted with an automatic flow control system to conserve water in the reservoir or deal with the variable loads. Large turbines usually use hydraulic governors that automatically adjust the flow of water into the turbine. For micro-hydro sized plants this method would be too expensive and be difficult to build and maintain locally. For this reason, a 3 phase AC induction motor will be used to move the internal flow control valve of the turbine. Because a sudden change in load is possible (30 – 40%) for micro-hydro plants, the electronic load controller will also be needed to respond to quick changes in load so that the village voltage does not exceed 220V. This report documents the process of building a test system comprising of a dynamic resistive load, microcontroller controlled resistive load, a three phase AC generator and a DC Motor. Where the dynamic resistive load represents the load of the village, the computer controlled resistive load would represent the community water heater, the three phase AC generator represents the Generator on site and the DC Motor together with its DC input voltage would emulate the turbine and its water flow respectively. The DC input voltage would be also controlled with a PWM signal through a delay loop to represent the water gate delay effects on the turbine as close as possible. With this, it would be possible to completely build and test a control system that emulates the dynamics of a water turbine generator.

LISA (Laser Interferometer Space Antenna) ist ein geplanter Gravitationswellendetektor, der aus drei Satelliten bestehen soll, deren Abstand mit Hilfe von Laserinterferometrie überwacht wird. Die hohe Frequenzstabilität der Laser, die dafür benötigt wird, soll mit einem dreistufigen Verfahren erreicht werden. Dieses beinhaltet eine Vorstabilisierung, die nicht nur hohe Stabilität sondern auch Durchstimmbarkeit aufweisen muss. Eine Möglichkeit so eine durchstimmbare Vorstabilisierung zu realisieren ist die Verwendung eines optischen Resonators mit eingebautem Piezoaktuator. Dies ist an sich kein neuer Ansatz, wurde bisher allerdings noch nicht mit der geforderten Stabilität realisiert. Im Rahmen dieser Arbeit wurden verschiedene piezoelektrisch durchstimmbaren Resonatoren aufgebaut und hinsichtlich ihres Rauschverhaltens und Durchstimmbereichs untersucht. Dabei konnte gezeigt werden, dass die Resonatoren alle Anforderungen an eine durchstimmbare Vorstabilisierung für LISA erfüllen. Darüber hinaus gibt die hier präsentierte Arbeit einen neuen Einblick in das Potential von piezoelektrisch durchstimmbaren Resonatoren. Ihre Stabilität ist nur eine Größenordnung geringer als die der besten nicht durchstimmbaren Resonatoren der gleichen Länge und das gemessene Rauschen kann dabei nicht nicht den Piezoaktuatoren zugeordnet werden. Es sollte also prinzipiell möglich sein noch bessere Stabilitäten mit piezoelektrisch durchstimmbaren Resonatoren zu erzielen. In der Tat zeigen theoretische Untersuchungen, die im Rahmen dieser Arbeit durchgeführt wurden, dass die intrinsische Stabilität eines Resonators durch den Einbau eines Piezoaktuators nur geringfügig herab gesetzt wird. Hoch-stabile piezoelektrisch durchstimmbare Resonatoren können über eine Verwendung in LISA hinaus auch bei zahlreichen anderen Anwendungen zum Einsatz kommen, wie z.B. in der Cavity Enhanced Spektroskopie als Transfer Resonatoren oder als optische Lokaloszillatoren in der Atom- und Molekülspektroskopie. / The Laser Interferometer Space Antenna (LISA) is a proposed space-based gravitational wave detector that aims to detect gravitational waves in the low frequency range from 0.1 mHz to 1 Hz, which is not accessible by ground-based detectors. It consists of three satellites whose distance is monitored by laser interferometry. The high frequency stability of the lasers required for this purpose is to be achieved with a three level noise reduction scheme. This includes a pre-stabilization stage that has to feature not only high stability but also tunability. One approach for such a tunable pre-stabilization is stabilizing a laser to an optical cavity with incorporated piezoelectric actuator. While this is not a new concept per se, it has never been realized with the required stability until now. Within this thesis, different types of piezo-tunable cavities have been built and thoroughly analyzed. It could be shown that the cavities fulfill all requirements for a tunable laser pre-stabilization for LISA. Furthermore, the work presented here gives a new insight into the potential of piezo-tunable cavities. Their performance is only one order of magnitude below that of the best non-tunable cavities of the same length and the measured noise can not be attributed to the integration of the piezo actuators. So, in principal, an even better performance should be achievable with piezo-tunable cavities. Indeed, theoretical considerations performed within this thesis reveal that the intrinsic stability of piezo-tunable cavities is only slightly inferior to that of rigid cavities. Beyond an application in LISA, highly stable piezo-tunable cavities are also valuable devices for numerous other applications. They can be used in cavity enhanced spectroscopy, as transfer cavities or as optical local oscillators in atomic and molecular spectroscopy.

Nous avons développé un oscillateur paramétrique optique simplement résonant (SRO) basé sur un cristal non linéaire de niobate de lithium dopé 5%-MgO et périodiquement polarisé (ppMgCLN). Il est pompé à 1064 nm par une diode laser en cavité étendue balayable continûment de 1050 à 1070 nm injectant un amplificateur Yb-fibré de puissance 10 W. Il génère une onde idler comprise entre 3 et 4 µm et une onde signal entre 1450 et 1650 nm. La cavité SRO est asservie sur le pic de transmission d'une cavité Fabry-Perot de grande finesse. Nous avons alors pu démontrer un balayage mono-fréquence sans saut de mode de l'onde idler sur 500 GHz. Cette large accordabilité continue pourrait être utilisée pour la spectroscopie haute résolution multi-espèces dans le moyen infrarouge. Par ailleurs, nous avons revisité la théorie ondes planes du SRO, dont les solutions analytiques ont été données pour la première fois en 1969 par Kreuzer sous la forme d'une équation transcendante, en utilisant une méthode perturbative très puissante qui tient compte de la déplétion de la pompe. Nous avons pu ainsi déterminer les relations d'entrée-sortie du SRO sous la forme de relations explicites très simples, montrant que les puissances de sortie sont proportionnelles à la racine cubique de la puissance pompe. / We developed a singly-resonant optical parametric oscillator (SRO) based on a nonlinear crystal of 5%-ppMgCLN congruent lithium niobate chip and pumped at 1064 nm by an extended cavity diode laser widely tuneable from 1050 to 1070 nm injecting a 10 W Yb-fiber amplifier. It generates an idler wave between 3 and 4 µm and a signal wave between 1450 and 1650 nm. The SRO cavity is stabilized to the top of a Fabry-Perot transmission fringe. We then demonstrated a mode-hop-free idler tuning range of 500 GHz. This broad continuous tunability could be used for multi-species high resolution spectroscopy in the mid-infrared. Moreover, we have revisited the plane waves SRO theory, whose analytical solutions were given for the first time in 1969 by Kreuzer in the form of a transcendental equation, using a very powerful perturbative method which takes into account the depletion of the pump. We were able to determine the input-output relations of SRO in the form of very simple explicit relationships, showing that the output powers are proportional to the cubic root of the pump power.