Thesis (MS)--Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: Christopher H. M. Jenkins. Includes bibliographical references (leaves 54-55).

1x8 optical power splitters on silicon substrate were successfully fabricated based on polyimide channel waveguides structure. The 1x8 power splitter was first designed by bean propagation method. The device was fabricated using polyimide provided by Eternal chemistry. The TE propagation loss of the waveguide is 1.4dB with a index contrast of 0.73%. However, the waveguide is not able to support low-loss propagation of TM polarized light. The chip size of the 1x8 power splitter is 17mm x 3mm. After fabrication, the optical characteristics of the splitter were measured.

A Y-branch optical power splitter based on the buried waveguide and the micro-prism waveguide bends is presented. The 132 splitter consists of a beam expanding region, a conventional Y-branch region, and two micro prisms providing large angle waveguide bends of device. The 132 splitter are fabricated by first depositing a 10-£gm-thick PECVD oxide (SiO2) on Si s ubstrates. The guiding core of the device was fabricated by etching trenches in SiO2 cladding, and filled with Benzocyclobutene (BCB) polymer. After etch-back process, the thin layer of spin on glass (SOG) is used to further planarized the surface of the device. The propagation loss of the waveguide is 0.47dB/cm at £f=1.3£gm. The normalized power transmission efficiency of the 132 splitter as large as 3.7dB was obtained. Simulation results based on beam propagation method (BPM) of the splitter is also presented.

A pair of light beams that have orthogonal polarizations and equal intensity can be generated through reflection and refraction of a monochromatic light at a dielectric surface. Sytematic procedures to design beam splitters which can produce such output light beams are described in this thesis. Two designs that are of particular interest are prismatic substrates coated by a single layer and a double layer of thin films. Specific examples of each beam splitter in the visible and infrared are included. The performance of each beam splitter as a function of incidence angle, film thickness, and wavelength is also discussed.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 65-67). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 65-67). Also available on the Internet.

Στην παρούσα εργασία μελετάμε τη λειτουργία των διαχωριστών δέσμης, καθώς και τη στατιστική κατανομή ενός και δύο σωματιδίων σε απλό και διπλό πηγάδι δυναμικού. Εξετάζουμε υπό ποιες συνθήκες τα δύο αυτά συστήματα μας δίνουν σύμπλεκτες καταστάσεις. Για τους διαχωριστές δέσμης καταλήγουμε στο συμπέρασμα ότι η καταλληλότερη διάταξή τους για να έχουμε μέγιστη απόδοση σύμπλεκτων καταστάσεων, είναι αυτοί να βρίσκονται σε διαδοχική σειρά μεταξύ τους. Από την άλλη μεριά, η μελέτη πηγαδιών δυναμικού, που έγινε γραφικά και αριθμητικά, μας έδειξε ότι τα γεωμετρικά χαρακτηριστικά τού κάθε πηγαδιού, δηλαδή το πάχος και το ύψος του, καθορίζουν τις ιδιοενέργειες τού συστήματος, τις πυκνότητες πιθανότητας των κυματοπακέτων και τελικά την πιθανότητα δημιουργίας σύμπλεκτων καταστάσεων. Γνωρίζοντας τη στατιστική κατανομή των σωματιδίων, ελέγχουμε τη συμπεριφορά τους άρα και την πληροφορία που αυτά μεταφέρουν. Τα παραπάνω βρίσκουν εφαρμογή στα qubits και τους κβαντικούς υπολογιστές. / In the current project we study the function of the beam splitters as well as the statistical behavior of one and two particles in a single and a double quantum well. We examine the conditions under which these two systems provide us with entangled states. For the beam splitters we come to the conclusion that the most appropriate array for having entangled states, is to put them in successive line. On the other hand, the graphical and numerical study of the quantum wells showed that the geometrical characteristics of a quantum well, that is to say thickness and height, define the energy of the system, the density probability of the wave packets and finally the probability for having entangled states. Having knowledge of the statistical behavior of the particles, we may then control the informations that they carry. All the above have many applications in qubits and quantum computers.

Quarter-wave retarders (QWR) that employ total internal reflection (TIR) and interference of light in a transparent thin-film coating at the base of a prism are presented. Explicit equations that guide the optimal design are provided. The optimal refractive index and normalized thickness of QWR coatings on glass and ZnS prisms are determined as functions of the internal angle of incidence from 45o to 75o. An achromatic QWR that uses an Si3N4- coated N-BK10-Schott glass prism is also presented with retardance error of 3o over the 400-600 nm wavelength range. An iterative procedure for the design of a polarizing beam splitter (PBS) that uses a form-birefringent, subwavelength-structured, one-dimensional photonic-crystal layer (SWS 1-D PCL) embedded in a high-index cubical prism is presented. The PBS is based on index matching and total transmission for the p polarization and total internal reflection for the s polarization at the prism-PCL interface at a 45o angle of incidence. A high extinction ratio in reflection ( 50 dB) over the 4-12 μm IR spectral range is achieved using a SWS 1-D PCL of ZnTe embedded in a ZnS cube within an external field of view (FOV) of ±6.6o and in the presence of grating filling factor errors of up to ±10%. Comparable results, but with a wider field of view, are also obtained with a Ge PCL embedded in a Si prism. A design for visible spectrum (553–713 nm) PBS SWS 1-D PCL of ZnTe embedded in a ZnS cube is also presented. The PBS shows a FOV of ±7o. A circular polarizing beam splitter (CPBS) with equal throughput for p and s polarization using SWS 1-D PCL embedded in a high-index cubical prism is introduced. A dual QWR in transmission and reflection with 50–50% CPBS is designed using the PCL. Such a CPBS shows large deviation from the design point as a result of small changes in the design parameters; e.g. a change of 10% in the filling factor results in 12o shift from the 90o phase shift between p and s polarizations, which limits the practical utility of the device.

This thesis is concerned with the guiding of cold atoms using optical forces, which is of great importance in the field of atom optics. Atomic beams can be used for precision sensor equipment, building nano-scale structures, construction of quantum computers and to further the understanding of the properties of atoms. Atoms are guided along light beams using the dipole force; there are two regimes under which this force works. Typically red-detuned guides are used (atoms are attracted towards the light) such guides, however, require large detuning and high powers. In this thesis we investigate the use of blue-detuned (atoms are repelled from the light) hollow light beams of moderate power (a few hundred mW) and confine atoms in the dark centre of the beams. Several magneto-optical traps (MOTs) have been constructed to exploit different guiding geometries. Hollow beams have been generated using a variety of methods; in particular the use of a computer controlled spatial light modulator (SLM) has provided great versatility and simplicity to the experimental arrangements. First, experiments were performed with a low-velocity intense source (LVIS) of atoms. A co-linear LG beam significantly enhances the observed flux, however, considerable difficulties are encountered loading atoms into oblique guides. Imaging a hole in the walls of the light tube was used to improve the loading efficiency. Second, guiding a free-falling atom cloud is performed using a non-diffracting Bessel beam. It is found that while the potential of the Bessel beam is steeper than equivalent LG beams the power distribution across the beam severely limits its usefulness. The next study investigated higher-order LG guide beams generated with an SLM. High order modes have a narrower profile so confine the atoms with less interaction with the guide beam, leading to a more natural guide (as opposed to a pushing force). Finally the SLM was used to create non-trivial beam shapes for beam splitters and interferometers.

Considerable research is being carried out into the parameters that affect catalyst performance in order to meet the latest emission regulations. The conversion efficiency and the durability of automotive catalytic converters are significantly dependent on catalyst flow performance. Related investigations are commonly conducted using CFD techniques which represent an inexpensive and fast alternative to experimental methods. This thesis focuses on the flow performance of automotive catalytic converters using both experimental and computational techniques. The work describes the effects of inlet flow conditions on catalyst performance, the application of radial vanes to catalyst systems and the refinement of the CFD flow model which increases the accuracy of the predicted catalyst flow performance. the effects of inlet flow conditions on the flow maldistribution across the catalyst face and the total pressure loss through the system were assessed using a steady air flow rig. Tests were conducted over a range of Reynolds numbers typically encountered in automotive catalytic converters using a uniform and a fully-developed inlet flow condition. The results showed that the flow maldistribution significantly increases with Reynolds number notably in wide-angled diffusers. The catalyst flow performance is considerably improved when the inlet flow is uniform rather than fully-developed, the non-dimensional total pressure loss is reduced by 8% at Re=60000 and the flow maldistribution across the catalyst face is decreased by 12.5% and 15% respective Reynolds numbers of 30000 and 60000 when using a 60 degree diffuser. The total pressure loss through the system was found to be mostly associated with the monolith brick resistance. When the flow maldistribution is approximately 2, the pressure loss across the monolith brick represents 80% of the system pressure loss. The flow maldistribution across the catalyst face was improved by locating a system of radial splitters in the diffuser. The optimum flow performance was found to be a complex function of the vane design. A maximum improvement in the flow maldistrution indices M and Mi of 25% and 50% respectively was achieved at the expense of an increase in total pressure loss of 13.5% at Re = 60000. Both CFD and flow visualisation techniques were used as an aid to interpreting the flow field in the diffuser. Although a qualitative agreement was obtained using CFD, the flow maldistribution across the catalyst face was underpredected by up to 20%. The accuracy of the flow predictions was significantly improved by investigating the flow field in the monolith channels. Flow recirculation occurs in the channel entry length when the flow approaches the monolith channels at an angle which induces an additional implemented into four models of the flow through axisymmetric catalyst assemblies using various diffuser geometries and inlet flow conditions. By including the flow entrance effects in the porous media approach, the flow maldistribution was predicted within 8% instead of 15% when these effects are neglected. Further investigation of the flow in the monolith channels will be required to accurately model three-dimentional flows (racetrack catalysts) and to include various channel geometries and system flow rates.