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The intensity dependent refractive index change of a medium is frequently described in terms of the product n₂ · I where n₂ is the nonlinear refractive index and I the light intensity. The nonlinear refractive index is often treated as constant which is a reasonable assumption if the light interacts only with bound electrons. In the case of carbon disulfide (CS₂) however, nuclear motions contribute to n₂. These motions occur on the sub picosecond time scale and thus become especially relevant for ultrashort laser pulses. The neat liquid CS₂ is studied because it exhibits a large nonlinear refractive index in comparison to other liquids. Therefore, it is employed in optical switching, optical limiting, and beam filamentation applications. This thesis presents effective n₂ values for Gaussian shaped linearly polarized pulses with central wavelength at [lambda]= 700nm. A theoretical model describing the time evolution of the material response is applied to distinguish between the instantaneous electronic, the ultrafast nuclear and the slow nuclear origins of the nonlinear refractive index. Moreover, the tensor nature of the material response function is studied by means of circularly polarized light. The relative magnitudes of bound electronic and nuclear contributions to n₂ are experimentally determined. Eventually, the dispersion of the instantaneous electronic response is measured in the spectral range between 390nm and 1064nm.

This dissertation describes the development of novel techniques for characterization of nonlinear properties of materials. The dissertation is divided into two parts, a background and theory section and a technique development section. In the background and theory section we explain the origins of the nonlinear optical response of materials across many different spatial and temporal scales. The mechanisms that we are most interested in are the electronic nuclear and reorientational responses, which occur on the range of sub-femtosecond to several picoseconds. The electronic mechanism is due to the electrons of a material experiencing a non-parabolic potential well due a strong electric field and occurs on the sub-femtosecond timescale. The nuclear or vibrational effect results from the motion of the nuclei of the atoms and typically occurs on the order of a few hundred femtoseconds. Finally the reorientational nonlinearity is due to the alignment of the molecule to the electric field, which alters the polarizability of the molecule and typically occurs on the scale of a few picoseconds. There are other mechanisms can induce nonlinear optical effects such as thermal effects and electrostriction, but these effects typically occur on much larger timescales than we are interested in, and hence will not be a major focus of this dissertation. In the nonlinear characterization techniques section, we describe previous research into the field of nonlinear optical characterization techniques, describing the techniques used to characterize the nonlinear properties of materials, their applications and limitations. We will trace the development of two recently developed techniques for nonlinear spectroscopy − the Dual Arm iii Z-Scan and the Beam Deflection techniques. The Dual Arm Z-Scan technique is an enhancement of the standard Z-Scan technique that allows for the measurement of small nonlinear signals in the presence of large background signals. This technique allows for the measurement of materials under certain conditions not previously measureable using the standard Z-Scan technique, such materials with low damage thresholds, poor solubility and thin films. In addition to the Dual Arm Z-Scan, we have developed a new method for characterizing nonlinear refraction, the Beam Deflection technique, which is a variation of the photothermal beam deflection technique previously used to measure very weak absorption signals. This technique offers relative ease of use, the ability to measure the absolute magnitude and sign of both the real and imaginary parts of � (3) simultaneously with high sensitivity. We fully develop the theory for materials with instantaneous and non-instantaneous nonlinearities, with nonlinear absorption and group velocity mismatch. We also demonstrate the power of this technique to separate the isotropic and reorientational contributions of liquids by examining the temporal response and polarization dependences. Lastly, we summarize our conclusions and describe two promising future research directions that would benefit from the Dual Arm Z-Scan and Beam Deflection techniques

As patient access to laboratory testing outside the clinic grows, healthcare providers can expect to confront increasing questions about the utility and interpretation of consumer-initiated laboratory tests, including germline genetic testing. The aim of this study was to characterize the current marketplace diversity of what has traditionally been labeled “direct-to-consumer” genetic testing options. A horizon scan was carried out with lab tests meeting the following criteria: (1) available for purchase in U.S. between October 1, 2019, and September 30, 2021, (2) capable of using germline genetic testing to assess risk of at least one diagnosable health condition, and (3) ability to purchase without visiting a provider. We will refer to these tests as “consumer-initiated tests”. Searches were completed of the National Center for Biotechnology Information’s Genetic Test Registry, the U.S. Food and Drug Administration’s list of nucleic acid-based tests, and the International Society of Genetic Genealogy Wiki webpages. In addition, searches were performed on the three largest U.S. search engines and the three largest online retailers. In the initial search, 300 labs were identified. The websites of these laboratories were then reviewed for test offerings that matched the criteria for this study; labs without tests meeting these criteria were eliminated. Information regarding the ordering process, test characteristics, and return of results was abstracted from and validated by the webpages, sample test reports, and lab contacts through email and/or phone. In the final review of 21 laboratories that offered these tests, two primary models of testing were identified. In Model 1, a participant could pay for testing without any provider involvement. In Model 2, a participant could order a test after electing review by a company-affiliated healthcare provider. Methodologies varied from array-based genotyping to whole genome sequencing, and companies reported individual variants, complex traits, or both. Several labs also offered report customization, reporting of variants of uncertain significance, raw data downloads, and added health reports. The market for participant-initiated genetic testing for health risks continues to grow as patients seek information about their disease predisposition outside of traditional healthcare settings. Moreover, these patients can obtain raw data for reinterpretation through these testing modalities. Understanding these many test offerings can better equip primary care providers in fielding patient questions on resources such as this.

<p> The design of a flexible, high speed, raster scan graphics terminal is presented. The design is presented in general architectural terms rather than from a detailed circuitry point of view.</p> <p> Control is divided between the 'main' microprocessor, an Intel 8086, and a subservient graphics controller which consists of a microprogrammable, bit-sliced, AM2903/2910 special purpose microprocessor. The high speed graphics controller is microprogrammed to accept basic line and circle generating commands. The configuration is felt to represent an efficient balance between simplicity and speed.</p> / Thesis / Master of Science (MS)

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