Thesis (Ph. D. in Physics)--University of California, Berkeley, Jan. 1961. / "UCRL-9390." Includes bibliographical references (leaves 112-115).

Thesis (Ph. D. in Physics)--University of California, Berkeley, Sept. 1960. / "UCRL-9251." TID-4500 (15th ed.). Includes bibliographical references (leaves 36-37).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2011. / Printout. Includes bibliographical references (leaves 56-58). Also available on the World Wide Web.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references (leaves 62-68). Also available in electronic version.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 119-133). Also available in electronic version.

The fluctuations of the constituent populations in a multi-level system are considered as applied to a three and four level semiconductor model. It is shown that under certain conditions the fluctuations of the electron numbers in the conduction band can be super-poisson, defined as having a variance greater than the mean number. The general autocorrelation function for a three level system is obtained. For certain limits, this correlation function is the sum of two damped sinusoidal terms. This would indicate there is an oscillatory interaction between the population numbers. The photon distribution as a function of position within a one-dimensional active medium is derived. When two partially reflecting mirrors are situated at both ends of the medium, the stationary photon distribution obtained is a function of the cavity amplification and the mirror reflectivities. The distribution of photo-electrons emitted from a detector of area A and resolving time T when illuminated by an incident light beam is derived. By using a binomial rather tha a deterministic quantum efficiency an additional term is obtained in the autocorrelation function. The resulting spectral density of the photo-current fluctuations is shown to be the sum of a Poisson particle noise and wave interference term. Several examples of different spectral line shapes are discussed. Also considered is an intensity modulated light beam. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Photoelectric mixing in a photodiode is used In this work as a statistical spectroscopic tool. A number of experiments were performed to determine the fluctuation spectrum generated by this process and the statistical properties of the light which might be deduced from the data. Due to practical limitations in attainable temperatures, blackbody sources were not able to produce an observable mixing above shot noise. Experiments were also carried out using line spectra from gas discharge lamps. The best source available was a 300 W Xenon lamp, emitting lines in the red, which under optimum conditions produced excess current fluctuations equal to 60% of shot noise. The observation of photoelectric mixing losing a gas laser source has already been reported in the literature, but the Gaussian distributed electric field model usually applied does not fit the experimental results. A new model was proposed in this thesis which considers the laser light as a narrow band of coherent light embedded in a relatively broad band of spontaneous light. Mixing between the signal and the spontaneous emission was considered to be the only observable effect due to experimental limitations. This model appeared to fit the data and gave some information about the statistical properties of the laser beam. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A MOS optical sensor that utilizes avalanche multiplication in silicon is proposed and investigated both theoretically and experimentally. The above-breakdown operating regime is discussed and it is shown how a MOS photosensor may be operated in a photon counting mode by pulsing it into very deep depletion, beyond the point where avalanche "breakdown normally occurs. Avalanche discharges in such a MOS sensor are self-quenching due to the formation of an inversion layer. This self-quenching property suggests that a monolithic self-scanned array of MOS photon counting sensors should be possible. It is described how specially designed charge-coupled arrays (PC-CCD's) could be operated in this new regime. The high response of silicon in the visible and near infrared, compared with the responsive quantum efficiency of the commonly-used photocathode materials, gives the proposed imager a distinct advantage over presently-existing photon counting sensors in these spectral regions. It is shown that a PC-CCD must be fabricated on a p-type silicon substrate and illuminated from the back side in order to obtain a high avalanche initiation probability for the photogenerated carriers. It is also shown that all thermally activated, steady-state dark generation of carriers can be reduced to a negligible level by cooling the sensor to 100 K or less, while the generation due to interband tunneling may be reduced to an acceptable level by ensuring that the peak fields within the depletion region remain below approximately 4.3 x 10⁵ Vcm⁻¹. The dark generation due to band-to-band tunneling via trap states may make it necessary to restrict the peak fields to even lower values. Re-triggering following a breakdown pulse, due to charge trapping or impact ionization of these traps during the avalanche, is also analysed. Optical coupling due to light emission during the avalanche discharges is discussed and two methods for the prevention of this coupling between the image elements in linear arrays are described. MOS gates that break down either at the Si-SiO₂, interface, or in the bulk at a n-p junction created by a buried n-channel, have been fabricated and operated above breakdown. The surface breakdown devices were operated in a charge-injection mode while the bulk breakdown devices were operated in a charge transfer mode similar to that which would occur in a full PC-CCD imager. The surface breakdown devices exhibited excessive dark count rates that were attributed to the high electric fields at the Si-SiO₂ interface. The bulk breakdown detectors were found to be far superior. They had very sharply peaked pulse height distributions and considerably lower dark pulse rates. Operation up to 12 volts above breakdown with a corresponding avalanche initiation probability greater than 0.9 was possible with these devices. Only a very weak temperature dependence of the dark pulse rate was observed, suggesting that a tunneling mechanism of dark carrier generation was limiting the performance of the bulk-breakdown devices. The magnitude of the dark count rate agreed with that expected for band-to-band tunneling through mid-gap states. These states, through a change in their occupancy during breakdown, were also believed to cause the re-triggering of avalanches that was observed when operating at high, above-breakdown voltages. These limitations on performance can be expected to be removed by employing improved processing techniques which would reduce the mid-gap trap levels by one or two orders of magnitude. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

A thesis submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the requirements for the degree of doctor of philosophy (Physics) School of Physics. University of the Witwatersrand, Johannesburg. 24 March 2017. / This thesis is an accumulation of the work and that was carried out and published as two articles and two book chapters. Throughout the thesis, we develop and present theoretical as well as numerical model to extend the existing techniques to study the optical properties of photonic crystals, plasmonic photonic crystals and photonic quasicrystals. We start with a background review, where we cover the theoretical aspects of light–matter interaction. That is followed by a review of the physics of photonic crystals. In that chapter, we discuss the different properties of photonic crystals, plasmonic photonic crystals as well as the topic of localization. We then delve into the numerical aspects of the subject. We provide a review on the frequency domain method and the finite–differences–time–domain methods which they are both used in the work to perform different types of simulations. The frequency domain method is, then, extended to enable the numerical analysis of the optical properties in plasmonic photonic crystals. We use first order perturbation theory to study the effect of surface plasmon polaritons on the photonic band structure of plasmonic photonic crystals. We developed a simple numerical tool that extends the standard frequency domain methods to compute the photonic band structure of plasmonic photonic crystals. We then employ the two stage cut and project scheme to generate a dodecagonal two–dimensional quasiperiodic structure. The finite-differences-time–domain method is applied to simulate the propagation of electromagnetic modes in the system. We compute the transmission coefficients as well as the inverse participation ratio for a quasicrystal consisting of dielectric cylindrical rods. The analysis has shown that crystal has critical states. Furthermore, we apply the frequency domain method to quantify the localized modes in the vicinity of defects in a two–dimensional photonic crystal. We compute the intensity of those modes in the surroundings of the defects sites to identify their nature. Finally, we use the finite–differences–time–domain method to provide a second example of a quasicrystalline structure, where the states are localized. / GR2018