In the past thirty years, high power laser technology has been dominated by Nd:YAG as the gain medium. The pump wavelength of Nd:YAG is 808nm, and the lasing wavelength is 1064nm. It is categorized as four-level laser. The pump wavelength of Yb:YAG is 940nm, and the lasing wavelength is 1030nm. It falls into quasi-three-level laser category. Because Yb:YAG have higher quantum efficiency and less surplus heat, it have the potential to replace Nd:YAG. The purpose of this study is to develop a multi-reentrant two-mirror Yb:YAG ring laser. In this thesis, we will introduce multi-reentrant two-mirror ring laser. The thermal problem of quasi-three-level laser was overcome by multi-wavelength coating on gain medium and input/output couplers, numerical simulation for mode match, and efficient TE-cooling for laser crystal. This symmetrical two-mirror figure ¡§8¡¨ ring cavity has the merit of compact, few optical elements, and easy design. The 1030nm output laser of our ring cavity promises to make the design widely applicable to solid-state lasers, such as single longitudinal lasers and mode-locked lasers.

Diode laser pumped solid state laser is compact, and can generate high peak power laser with good output mode. It has been applied extensively in electronics, communication, and medical treatment in recent years. The purpose of this study is to develop a compact and practical ring laser system. The multi-reentrant ring laser system developed in this work composes of two spherical mirrors and a gain medium where the conventional ring laser systems have at least three mirrors to construct the laser cavity. The laser system is more compact and simple than conventional ring laser systems. It can be used for producing single frequency green and blue lasers. The laser system can also be applied in aviation, trace detection as well as compact picosecond mode-locked laser. We not only prove that the multi-reentrant laser system is feasible theoretically and experimentally, but also use the fundamental laser theory to find the relation among cavity length, number of points, number of circulation, and the distance between center of gain medium and optical axis. The exact solution we obtained is experimentally verified with good agreement. A comparison between exact solution and paraxial approximation is also performed. The beam paths observing from the top, side, and end view are analyzed for various multi-reentrant laser cavities. The stability of the cavity is numerically analyzed and experimentally verified with good agreement, too. Finally, the differences in cavity configuration between TEM01 mode and the figure-8 mode are compared in this thesis.

With ever-increasing demands for high-speed data transmission and device capacity to handle various telecommunication data links, the high reliability of these transmission devices is expected for uninterrupted service. A typical optical communication system consists of transmitters in which laser diodes convert electrical signals into light signals, optical fibers with a few pumps transmitting and maintaining these light signals over long distances, and receivers in which photodiodes convert the light signals back into an electronic form. The efficiency of optoelectronic devices in a communication system, which include transmitters and receivers, plays the most important role in determining the quality and the bandwidth of a communication system. For transmitters, the efficiency is defined as the ratio of the light entering the optical fiber to the light generated by the laser diode. Therefore, the optical fiber should be aligned as precisely as possible with the laser diode to ensure the high efficiency. For high performance optoelectronic devices, box-type packages including the dual-in-line package (DIP) and butterfly package with fiber-solder-ferrule (FSF) are widely used. An optical fiber with a metallized end is soldered inside a ferrule tube to form the FSF. The FSF is joined on a u-channel mount in front of laser diode by laser welding. No matter where the fiber locates in the ferrule tube, the place for maximum coupling power can be dynamically measured and then the FSF is fixed. But, researches have shown that the redistribution of residual stress and the stress relaxation of creep phenomenon within the solder will push the fiber shift to the geometrical center of the ferrule and the shift reduces the coupling efficiency of laser module after temperature cycle testing. The efficiency is worse when the initial fiber eccentric offset increased. An optimum approach for reduction of the fiber alignment shift in laser module is to solder the fiber near to the center of the ferrule. A method for automating the FSF packaging process has been developed to fix the fiber within less than 20um of the center of the ferrule. This method makes use of CCD cameras as position sensors to locate the fiber, and compensates all the major sources of inaccuracy resulting from a typical CCD-based packaging system. The accuracy of the fiber position is highly improved from 80um by traditional packaging process to 20um shown in the experiments. Further work is underway to better the accuracy by compensating the minor sources of inaccuracy.

In this thesis, ridge waveguide laser, quantum well intermixing, 1x1 and 2x2 optical switching and ring resonator with multimode-waveguide turning mirror couplers have been investigated. We develop a new design that the perturbation is the minimum when the crossing occurs at the self-image location in a low-loss multimode waveguide. We use a center-fold low-loss multimode waveguide with a single self image at the center. Such waveguides can cross at 90 degrees or 60 degrees at the center with minimal cross talk. One can reflect the incident mode into an intersecting waveguide by introducing an idea reflecting plane. In practice, the reflector is replaced by a plane for total internal reflection with correction for Goos-Hanchen shift. Passive component for£f = 1.41 £gm samples, 1x1 60-degree multimode-waveguide turning mirror, 1x1 90-degree multimode-waveguide turning mirror, 2x2 90-degree multimode-waveguide turning mirror and a single ring resonator with 2x2 multimode-waveguide turning mirror couplers have been fabricated. (1) The multimode-waveguide turning mirror coupler with cross coupling factor (K) of 0.15 is achieved by an etched facet with a correction for Goos-Hanchen shift. (2) The length of the multimode-waveguide turning mirror coupler is only 33% of the length of conventional straight 2x2 MMI coupler with K=0.15. (3) The circumference of the curve waveguide in this ring resonator is decreased by 50%. (4) The characterization of the InP-based single ring resonator incorporating 2x2 multimode-waveguide turning mirror couplers with K= 0.15 has a free spectral range of 82 GHz, a contrast of 4 dB, and a full-width at half-maximum (FWHM) of 0.24 nm for the drop port. (5) This single resonators in In0.53Ga0.47As/In0.53Ga0.26Al0.21As grown by molecular beam epitaxy (MBE), and In0.67Ga0.33As0.6P0.4/In0.71Ga0.29As0.74P0.26 grown by metal organic chemical vapor deposition (MOCVD) have been demonstrated, respectively. We have also developed quantum well intermixing technique for the photonic integration. (1) Argon plasma bombardment followed by rapid thermal annealing for InGaAs/InGaAlAs multiple-quantum-well structures grown by MBE has been found to strongly enhance the intensity of room-temperature photoluminescence signal by more than an order of magnitude. The strength of the photoluminescence signal is found to be dependent on the plasma RF power and bombardment time. The resulting blue shift of the photoluminescence wavelength due to quantum well intermixing is found to be under 15 nm. (2) Process combining inductively-coupled-plasma reactive ion etching (ICP-RIE) and SiO2 sputtering film has been investigated for the InGaAsP and InGaAlAs multi-quantum wells (MQWs). Optimal distance is of 300 nm for InGaAsP, and of 200-nm-thick for InGaAlAs between MQWs and the upper cladding by ICP-RIE and bombardment. The process resulted in a bandgap blue-shift of 90 nm for InGaAsP, and of 60 nm for InGaAlAs. The result is very useful to regrown, the sacrificing layer and to integrate the fabrication.

Imaging has revealed that brain activation of verbs with verifiable products (‘throw, kick’) activate language areas as well as the motor cortex responsible for the performance of the action described. An exploratory comparison of eye related verbs with no verifiable products (‘observe’) to mouth related verbs with verifiable products (‘shout’) has revealed a similar activation pattern. Thus in order to further study mental action verbs with no verifiable products, the present two-part study used words that were suitable across two modalities (e.g. you can ‘perceive’ both through vision and audition) and compare them to themselves under differing contexts of auditory and visual verbs so as to eliminate any word characteristics differences, as well as explored the two modalities directly. The primary purpose was to delineate whether associative learning or the mirror systems theory might better account for the acquisition of this unique subclass of verbs. Results suggest that Mirror systems theory more likely accounts for the observed cognitive processing differences between the two verbs. Keywords: Verbs, language, Event-related potentials, abstract, associative learning theory, mirror systems theory.

The push towards larger diameter space telescope mirrors has caused the space industry to look at lightweight, deformable alternatives to the traditional monolithic mirror. One possible solution to the dilemma is to use the piezoelectric properties of certain materials to create a lightweight, deformable mirror. Current piezoelectric deformable mirror designs use individual actuators, creating an immensely complex system as the mirrors increase in size. The objective of this thesis is to aid in the design and development of lightweight, deformable mirrors for use in space based telescopes. Two topics are considered to aid this development. A doubly curved, lightweight, bimorph mirror is investigated. The fabrication method entails forming a thin film piezoelectric polymer into a doubly curved shape using a specially designed forming machine. The second topic entails the finite element modeling of a composite mirror substrate with a piezoceramic actuator backing. The model is generated using a meshing program designed to generate off-centered spot loads of electric potential. These spot loads simulate the actuation due to an electron gun. The effects of spot location and size on mirror deformation are examined.

Capacitive displacement sensors have many applications where non-contact, high precision measurement of a surface is required. Because of their non-contact nature they can easily measure conductive surfaces that are flexible or otherwise unable to be measured using a contact probe. Since the output of the capacitance gage is electrical, data points can be collected quickly and averaged to improve statistics. It is often necessary for capacitive displacement sensors to gage the distance from a curved (non-flat) surface. Although displacements can easily be detected, the calibration of this output can vary considerably from the flat case. Since a capacitance gage is typically factorycalibrated against a flat reference, the experimental output contains errors in both gain and linearity. A series of calibration corrections is calculated for rectifying this output. Capacitance gages are also limited in their overall displacement travel. A support stage is described that, along with control electronics, allow the properties of the capacitance gage to be combined with an interferometer to overcome this displacement limitation. Finally, an application is proposed that would make use of the capacitance sensor and support stage assembly.

There is no abstract available for this thesis.

The mirror, central to traditional Western epistemology and representation, has shattered. Yet its metaphors, mechanisms, operations and poetics continue to powerfully shape and evocatively describe, contemporary Western culture. The exhibition, After Reflection, investigates realist representation in a post-mirror paradigm, through paintings, prints and projections that incorporate perceptual plays, virtual imaging and digital modeling. The dissertation charts the history of the mirror metaphor and its reconfiguration through post-modernity. It suggests that while the metaphor may be superceded it remains useful and evocative but only if considered in the form of a mirror-ball rather than as a planar mirror. The dissertation examines the mirror metaphor and its relationship to a wide selection of aspects crucial to the arrangement of contemporary Western culture, art and space. / The thesis is structured as a mirror-ball, in small fragments that both reflect on and illuminate aspects of the topic. The dissertation is thus divided into various ‘Shards’ – broad subject headings derived from the primary mechanisms and poetics of the mirror. Within each shard are a varied number of ‘Rays’ – lines of illumination arising from each shard that impact on particular aspects of Western culture. / The exhibition After Reflection includes further speculations around the theme of the mirror and with the arrangement of contemporary space – both pictorial and actual. It is not intended to illustrate the dissertation but to be an additional supplement that visually elaborates on issues enmeshed and parallel to those addressed in the dissertation. The works have all been completed during the period of the candidature (from March 2000) They include six oil paintings, a set of Lightjet photographs (from the “Echohouse’ series) generated from 3d modelling programs and then face-mounted to Perspex. There is an additional three larger scale Lightjet photographs from another series. Finally there are projected works. One is a self contained DVD projection and the other is Mirror Land - a large scale 3d animation covering two wall and projected in a chiasmatic arrangement. Both works feature an endless looping repetition. / All the works play with metaphoric aspects of the mirror and examine the construction of space in contemporary Western culture. This space has become increasingly rationalized since the Renaissance and mirror a more general abstraction whereby the real is evermore preceded by simulations. The work looks at the mirror land and suggests a mode of realism capable of addressing the situation where the real has increasingly been reconfigured into representation.

Thesis (B.A.)--Haverford College, Dept. of Psychology, 2007. / Includes bibliographical references.