Thesis (Ph.D.) -- McMaster University, 1997. / Includes bibliographical references. Also available via World Wide Web.

This dissertation describes a proof-of-principle experiment demonstrating a technique for stable isotope enrichment called Magnetically Activated and Guided Isotope Separation (MAGIS) (1). Over the past century a large number of enriched isotopes have become available, thanks largely to electromagnetic separators called calutrons that were developed during World War II. These isotopes have found applications across an array of fields including medicine, basic science, and energy. Due to substantial maintenance and operating costs, the United States decommissioned the last of its calutrons in 1998, leading to demand for alternative methods of isotope separation. Our experiment suggests the promise for MAGIS as a viable alternative for replenishing stockpiles previously provided by calutrons. Our apparatus combines optical pumping with a scalable magnetic field gradient to enrich lithium-7 (Li-7) by suppressing lithium-6 (Li-6) throughput in a lithium atomic beam. We first evaporate lithium metal in a crucible in order to generate thermal, high flux beam. We then perform optical pumping on Li-6 atoms, magnetically polarizing a substantial fraction of Li-6 atoms into the entirely high-field seeking 2²S₁/₂, F = 1/2 ground state. The resultant beam then samples a magnetic field gradient produced by a 1.5 m long array of rare-earth permanent magnets bent over its length by 20 mrad. This geometry prevents high-field seeking lithium atoms from reaching the plane beyond the magnets, while efficiently deflecting low-field seeking atoms. We measured Li-6 suppression – using independent techniques – along the plane after the magnets beyond a factor of 200, corresponding to Li-7 enrichment to better than 99.95%. As apparatus-specific hindrances appeared to limit this suppression, we believe that we should achieve better enrichment on a commercial apparatus. We also measured both the absolute flux beyond the single, 1.5 in tall magnet array and the efficiency for guiding feedstock material to the collection plane. Given the planar configuration for the field gradient, the flux that we measured should scale linearly with both magnet height and the number of arrays surrounding the source. Our measurements therefore indicate that – at source temperatures that we actually investigated – a commercial apparatus fitting within a volume of just several cubic meters should yield hundreds of grams of enriched (to beyond 99.95%) Li-7 per year. In addition, we observed a competitive ratio between collected material and feedstock with greater than 20% of lithium incident upon the magnet array reaching beyond the magnets. Benchmarking our work against the calutron, we demonstrated comparable enrichment in a manner that should scale to the production of similar quantities. In contrast, however, MAGIS should require vastly less energy input. While calutrons required massive currents for maintaining a static magnetic field over a substantial area, the only non-shared energy expense for MAGIS is the cost for running the low power lasers for optical pumping. Via additional analysis, we have supplemented this proof-of-principle experiment with schemes for applying MAGIS to over half of the stable isotopes in the periodic table. Due to the success of this demonstration and the broad applicability of the principles, we believe that MAGIS will play an important role in the future of stable isotope enrichment. / text

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Physics. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / by Zbigniew M. Drozdowicz. / Ph.D.

Thesis (BSc. (Hons))--Australian National University, 2002. / Available via the Australian National University Library Electronic Pre and Post Print Repository. Title from title screen (viewed Feb. 18, 2003). "A thesis submitted as partial fulfillment of the requirements for the degree of Bachelor of Science with Honours in theoretical physics at the Australian National University" Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 138-140).

In this study, we fabricated an electrically wavelength-tunable resonant-cavity light emitting diode (RCLED). It was achieved by the combination of an AlGaInAs quantum well structure with an intra-cavity liquid crystal material. In the phase modulator layer, we used nematic liquid crystal (NLC) and cholesteric liquid crystal (CLC), respectively, comparing their difference in the infrared-spectrum. When inserting NLC, the anisotropic properties of liquid crystal enable continuous tuning of mode emission along the extraordinary direction and provide a 58 nm tuning range. The optical characteristics of this device are polarization dependent. On the contrary, the CLC-based device is polarization independent because any polarization of incident light experiences the same averaged refractive index. However, the phase difference of CLC is less than NLC, only a 41 nm tuning range of this sample. We also simulated and discussed experimental results of NLC-based RCLED. The optical pumping of the active region is realized by a CW laser at 1064 nm wavelength and observed at room temperature.

Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains xi, 121 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 106-107).

Thesis (Ph. D.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains v, 152 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

Thesis (MSc (Physics))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This thesis consists of two parts; the first part is a discussion on the detailed history of the development of different types of modelocked lasers, especially the neodymium-doped lasers. The second part describes the design and development of a modelocked diode-end-pumped solid state Nd:YVO4 laser using Semiconductor Saturable Absorbers. The first part of this work will cover the history of modelocking where different types of lasers were used to generate ultrashort pulses. The discussion will mainly focus on neodymium-doped lasers such as Nd:YVO4, where we will look at the spectral properties such as energy levels, absorption and emission wavelengths of such a laser. The discussion will also look at different types of optical pump sources; such as diode lasers and flashlamps, where we will see the advantages of using diode lasers as pump sources due to their better operating conditions and efficiency. We will also look at two different types of diode pumping setup schemes, which are end-pumping and side pumping; where we will discover that diode-end-pumping is a better scheme for laser mode matching resulting in high efficiency and very good beam quality when compared to side pumping. The gain bandwidth of the laser material will also be discussed showing that a laser material with a very large gain bandwidth and broad emission bandwidth is suitable for generating ultrashort pulses, such as Ti:Sapphire crystal. The discussion will also cover ultrafast lasers that have a small amplification bandwidth suitable for diode-end-pumping and that produce high average output power. Ultrafast lasers with low amplification bandwidth such as Nd:YAG and Nd:YVO4 will be discussed showing that they can generate very short pulses with durations of down to 19 ps and 20 ps respectively and average output powers of 27 W and 20 W. The technique of creating ultrashort pulses which is called modelocking will be discussed, where passive modelocking will be shown to be more suitable for creating ultra short pulses in the femtosecond region and active modelocking in the picosecond region. The discussion will also cover saturable absorbers for passive modelocking where we will discuss the use of semiconductor saturable absorber mirrors to generate reliable self starting modelocked pulses. We will also cover the instabilities associated with using saturable absorbers where we will discuss different methods for reducing the instabilities by using gain media with the smallest saturation fluence. The second part of the work will deal with the design and development of SESAM modelocked diode-end-pumped Nd:YVO4 lasers. This part will include a discussion on the resonator design criteria’s for achieving a stable modelocked diode-end-pumped solid-state laser. The choice of using Nd:YVO4 as a gain medium will be shown to be influenced by its large cross sectional area, which is useful in increasing the gain bandwidth for possible ultrashort pulse generation. The resonator for high power continuous wave (cw) output has been designed using simulation software developed at St Andrews University. We will also discuss stability criteria such as the laser spot size inside the crystal and on the end mirror and how they can be incorporated into the resonator design software. The discussion will also include the pump setup design and the efficient cooling method of the crystal using a copper heat sink. The methodology of obtaining stable, thermal lens invariant, single transverse mode operation during power scaling of Nd:YVO4 lasers will be discussed. A lens relay approach is used to extend the cavity length so as to introduce spot size control in the designed diode-end-pumped Nd:YVO4 laser that will be shown to produce a maximum average output power of 10.5 W with an average beam quality factor M2 of 1.5. We will also discuss the incorporation of a single quantum well SESAM within the extended diode-end-pumped Nd:YVO4 laser resulting in cw-modelocked pulses at an average output power of 2.8 W with pulse repetition frequency of 179 MHz, equivalent to the cavity round trip time of 5.6 ns. The incorporation of the double quantum well SESAM will also be shown to produce stable Q-switched modelocked pulses at an average output power of 2.7 W with pulse repetition frequency of 208 KHz. / AFRIKAANSE OPSOMMING : Hierdie tesis bestaan uit twee dele. Deel 1 is ‘n indiepte bespreking rondom die ontwikkelingsgeskiedenis van Modusgebonde lasers, veral van Neodemiumdoteerde lasers. Deel 2 beskryf die ontwerp en ontwikkeling van ‘n Modusgebonde diodeentgepompde vastetoestand Nd:YVO4 laser deur van ‘n Halfgeleier Versadigbare Absorbeerder (SESAM) gebruik te maak. Die eerste afdeling fokus op Modusbinding om ultrakort pulse te ontwikkel in verskillende tipes lasers. Die bespreking sentreer rondom Neodemiumdoteerde lasers soos Nd:YVO4. In hierdie geval beskou ons ook die spektraaleienskappe van die laser vir beide die absorpsie en emissie golflengtes. Verder word verkillende tipes pompbronne ondersoek (soos diodelasers en flitslampe). Die voordele van diodelasers kom sterk na vore a.g.v. beter werking en effektiwiteit. Verskillende pompopstellings word ook ondersoek naamlik ent-en kantpomping. Entpomping kom hier na vore as die beter opsie i.t.v. laser-moduspassing. Dit lei tot ‘n hoër effektiwiteit wat ‘n beter straalkwaliteit tot gevolg het, in vergelyking met kantgepompde opstellings. Die versterkingsbandwydte word ook bespreek: ‘n groot versterkingsbandwydte en breë emissiebandwydte is geskik om ultrakort pulse te ontwikkel. Ti:Saffier is ‘n goeie voorbeeld. Ultravinnige lasers met ‘n klein versterkingsbandwydte word ook bespreek aangesien dit geskik is vir diodeentpomping wat dan ‘n hoë gemiddelde uitsetdrywing lewer. Nd:YAG en Nd:YVO4 word ondersoek en daar word getoon dat hul pulse van so kort as 19 ps en 20 ps onderskeidelik teen ‘n gemiddelde uitsetdrywing van 27 W en 20 W kan lewer. Die tegniek waarmee ultrakort pulse geskep word is Modusbinding: passiewe modusbinding is meer geskik vir femtosekonde pulse en aktiewe modusbinding is meer geskik vir pikosekonde pulse. Verder word versadigbare absorbeerders bespreek, vir hul gebruik in die betroubare selfinisiërende modusgebonde pulse. Die onstabiliteite geassosieer met versadigbare absorbeerders word ook bespreek asook verskillende metodes om dit te minimaliseer. Die tweede afdeling behandel die ontwerp en ontwikkeling van ‘n SESAM modusgebonde diode-entgepompde Nd:YVO4 laser. Die resonator ontwerpspesifikasies vir stabiele werking word ook bespreek. Die keuse van Nd:YVO4 as versterkingsmedium is a.g.v. die groot deursnitarea wat die versterkingsbandwydte verhoog, om ultrakort pulse te genereer. Die resonator vir hoë drywing kontinuestraal werking is ontwerp deur van St Andrews sagteware gebruik te maak. ‘n Bespreking van stabiliteitsspesifikasies soos die laser kolgrootte, binne die kristal asook op die entspieël volg, asook die pompmetodiek en effektiewe verkoeling van die kristal. Die totale metodiek rondom die verkryging van ‘n stabiele, termieselens invariante, enkele transversale modus laser word bespreek met die oog op drywingsverhoging. Die geval onder bespreking is waar die laser se kolgrootte beheer kan word op die entspieël deur die resonatorlengte aan te pas. Dit word getoon dat dit ‘n kontinuestraal laser van 10.5 W drywing kan lewer teen die maksimum gemiddelde straalkwaliteit van M2 = 1.5. Die byvoeging van ‘n enkele kwantumput SESAM in die laser het modusgebonde pulse tot gevolg. Die gemete waardes was 2.8 W gemiddelde drywing met ‘n pulsherhalingstempo van 179 MHz wat in lyn is met die pulsbewegingstyd in die resonator van 5.6 ns. Deur van ‘n dubbele kwantumput SESAM gebruik te maak word Q-geskakelde modusgebonde pulse verkry, teen ‘n gemiddelde uitsetdrywing van 2.7 W en ‘n pulsherhalingstempo van 208 KHz.

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