Thesis (PH. D.)--Clark university, 1922. / "Off-printed from the American journal of psychology, January, 1923, vol. XXXIV."

Thesis--Lund Institute of Technology, 1993.

Thesis--Copenhagen. / Includes bibliographical references.

Thesis (Ph.D.)--McMaster University, 2005. / Advisor: M. Jamal Deen. Includes bibliographical references (p. 175-186). Also available online.

The use of aspheric surfaces in optical designs can allow for improved performance with fewer optical elements. Their use has become common place due to advancements in optical manufacturing technologies. Standard interferometric testing of aspheric surfaces makes use of part specific null optics in order to match the test wavefront to the aspheric surface under test. Non-null interferometric testing offers the possibility to test a range of aspheric surfaces with a single interferometer design without the need for part specific null optics. However, non-null tests can generate interferograms with very high fringe frequencies that must be resolved and unwrapped, wavefronts with large slopes that must be imaged without vignetting, and induced aberrations which must be separated from the surface errors of the part. The main goal of this project was the construction of a non-null interferometer capable of testing the aspheric tooling used in the manufacturing of soft contact lenses. Sub-Nyquist interferometry was used to allow for large wavefront departures which generate high fringe frequency interferograms to be both captured and unwrapped. The sparse array sensor at the heart of the Sub-Nyquist technique sets limits on both the range of the parts to be tested and the design of the interferometer. Characterization of the interferometer was achieved through the reverse optimization and reverse ray tracing of a model of the interferometer and was aided by multiple measurements of the test part at shifted positions. The system was found to be capable of measuring parts with aspheric departure of over 60λ from the best fit sphere, which with introduced part shifts, generated over 300λ of OPD at the detector. The OPD introduced by the parts was measured to an accuracy of at least 0.76λ peak to valley and 0.12λ rms.

This dissertation addresses the design, development, calibration and performance evaluation of a pre-clinical imaging system called AdaptiSPECT. Single-Photon Emission Computed Tomography (SPECT) systems are powerful tools for multiple applications in small-animal research, ranging from drug discovery to fundamental biology. Traditionally, pinhole SPECT systems are designed with fixed imaging characteristics in terms of sensitivity, resolution and size of the field of view, that are dictated by the hardware configuration of the system. The SPECT system described in this dissertation can change its hardware configuration in response to the subject data it is acquiring in order to improve the imaging performance. We employed 16 modular gamma-ray detectors, each of which consists of a NaI:Tl scintillation crystal, a fused silica lightguide, and an array of 9 PMTs. The camera is designed to work with maximum-likelihood position estimation methods. These detectors are arranged into 2 rings of 8 detectors around an adjustable pinhole aperture. The aperture itself comprises three cylinders of different diameters, each with pinholes of different diameters. The three aperture cylinders are stacked together along the imager axis, and selection of the appropriate ring of pinholes is carried out by translating the entire aperture assembly. In addition, some sections of the aperture are fitted with shutters to open or close additional pinholes that increase sensitivity. We reviewed the method used to calibrate AdaptiSPECT, and proposed a new interpolation scheme specific to adaptive SPECT imaging systems where the detectors can move to multiple locations, that yields system matrices for any configuration employed during adaptive imaging. We evaluated the performances of AdaptiSPECT for various configurations. The magnification of the system ranges from 1.2 to 11.1. The corresponding resolution ranges from 3.2 mm to 0.6 mm, and the corresponding transaxial field-of-view ranges from 84 mm to 10 mm. The sensitivity of the system varies from 220 cps/MBq to 340 cps/MBq for various configurations. Imaging of a mouse injected with a bone radiotracer revealed the finer structures that can be acquired at higher magnifications, and illustrated the ability to conveniently image with a variety of magnifications during the same study. In summary, we have brought the concept of an adaptive SPECT imaging system as it was originally described by Barrett et al. in 2008 to life. We have engineered a system that can switch configurations with speed, precision, and repeatability suitable to carry out adaptive imaging studies on small animals, thus opening the door to a new research and medical imaging paradigm in which the imager hardware is adjusted on the fly to maximize task-performance for a specific patient, not, as currently, an ensemble of patients.

In this dissertation, the PMD measurements of field and laboratory optical fibre will be discussed. In the laboratory, temperature cycling of different configurations of fibre were tested. It is shown that the environmental temperature plays a significant role in determining the behaviour of PMD. The PMD of all fibres tested showed changes in the PMD when the environmental temperature was changing, but remained constant for constant temperatures. This is explained by the structure and thermal coefficients of the materials used to make up the fibres. It is found that the temperature gradient has a large effect on the magnitude of the PMD fluctuations. Field measurements were conducted on buried and aerial cable. It is shown that the PMD of aerial cables shows a higher degree of scatter than the PMD of buried cables. The scatter seen in the PMD can be attributed to changing environmental temperature as well as movement of the cable. The PMD of the deployed fibre is in all cases found to be considerably higher than the PMD of laboratory fibre. Age of the fibre, deployment conditions and installation procedures are believed to be responsible for the higher value. Long term monitoring of the PMD is also found to be critical when testing fibres. Over- or underestimations of the average PMD are often made in the field due to only a limited number of readings being taken. Having a large test ensemble of input states of polarization is shown to increase the accuracy of the results. For aerial cables, movement of the cable has the same effect as scrambling the input SOP and hence the results will be more accurate. Buried cables on the other hand show little movement and hence only one input SOP is often tested. Scrambling the input SOP will therefore increase the accuracy of these results.

Whispering gallery modes (WGM) microcavity have played an ubiquitous role due to their high quality factor Q and small effective mode volume $V_{eff}$. They are suitable for a broad range of applications and scientific research including cavity quantum electrodynamics (c-QED), sensing, parametric oscillation, frequency comb and so forth. The major nonlinear effect in silica is the Kerr nonlinearity that arises from the dependence of refractive index on the signal intensity. In this thesis, we focus on the theoretical analysis of Kerr and Raman nonlinear effects in a silica spherical microcavity. We derive several analytical models for various nonlinear effects, including self phase modulation (SPM), cross phase modulation (XPM) and stimulated Raman scattering (SRS). The first part of this thesis develops a theoretical framework to describe the impact of Kerr nonlinearity, especially SPM on WGM. First a mathematical formulation to express $\chi^{(3)}$ in spherical co-ordinates is developed. We define the effective mode volume $V_{eff}$ for the the first time to analyze SPM effects by taking $\chi^{(3)}$ tensor in spherical co-ordinates and it is found that the effective mode volume is always smaller than the physical volume of the microsphere. Simulation results show that whispering gallery mode undergoes a negative frequency shift proportional to the injected energy due to SPM. Later, we extended the analysis to describe the nonlinear interaction between two WGMs. An analytical model is developed to describe the XPM effect in microsphere. Expressions for effective mode volumes and effective nonlinear coefficients to describe XPM are derived analytically. It is found that, when the effective mode volume increases, effective nonlinear coefficient becomes smaller and hence, we achieve a lower frequency shift. An analytical expression for the coupling of whispering gallery mode is derived. The resonant frequency of a weak probe mode can be shifted by a strong pump mode due to XPM and the frequency shift of the probe is proportional to the pump energy. Also, An analytical expression for describing the Raman effect in a spherical microcavity is developed by including the delayed Raman response. The results show that the signal power is amplified due to the SRS effect. / Thesis / Master of Applied Science (MASc)

No description available.

The switching energy and speed of a bistable GaAs etalon have been measured. At liquid nitrogen temperature, the switch-on was achieved by injecting a high density of carriers with an above-band-edge 600-nm external pulse. A minimum energy of 1 nJ was required. The measured switching time was 200 ps, limited by the detector response time. The switch-off was obtained by heating the device with a 300-nJ external pulse and consequently shifting the Fabry-Perot peak. Switch-off time was about 40 ns. Room-temperature bistability was first achieved in a GaAs-AlGaAs superlattice etalon. Switch-on by a near-band-edge 845-nm pulse of 10-pJ energy was observed.