Thesis (MEng (ElectronSys))--University of South Australia, 1996

Thesis (M.S.)--Rochester Institute of Technology, 1993. / Typescript. Includes bibliographical references (leaves 147-148).

Thesis (Ph. D.)--University of California, San Diego, 1973. / Vita. Includes bibliographical references (leaves 236-242).

Thesis (M.S.)--Rochester Institute of Technology, 2005. / Typescript. Includes bibliographical references (p. 81-82).

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Time-domain Polarity Coincidence Correlators (PCC) have been studied for the possible extension of these theories to the spatial-domain in the context of an optical PCC. The existing body of knowledge has been found to be inadequate for direct application to the spatial-domain. However, by remodeling the type of clipper or hardlimiter used in the development of the existing theory from a signum (bipolar) clipper to a binary (unipolar) clipper, a new expression for the output signal-to-noise ratio of an optical PCC is developed. This modification is necessary to account for the unipolar nature of light intensity. Both the existing time-domain and new spatial-domain PCC expressions are valid for the case of additive narrowband (bandwidth much less than the signal frequency) Gaussian-distributed noise at the inputs of the correlator. An optical experiment was constructed to evaluate a new type of binary spatial light modulator, the Litton Data Systems 128 x 128 Magneto-Optic Array. To accomplish this, a noiseless single frequency (fc) sinusoidal one-dimensional reference was correlated with a sinusoidal signal of equal frequency and phase to which gaussian-distributed noise was added. Both signals were hardlimited prior to correlation. Noise sources having bandwidths of 0.1 fc and0.5 fc were investigated to test the robustness of the narrowband constraints. The input data sets had signal-to-noise ratios of -10.0dB and -20.0dB. For both of these conditions the experimental data was found to be in excellent agreement with the new expression for the narrowband case. In the wideband case, the results were significantly different from the new expression, thereby corroborating the necessity of meeting the narrowband constraint. Both the time-domain and spatial-domain expressions are highly-dependent on the output filtering (after hardlimiting and multiplication) characteristics. The effect of filter insertion loss, at the signal frequency (fc), for the unipolar or optical case was examined as part of this research. It was found that the output signal-to-noise ratio increases as the carrier frequency components are attenuated. This affect, which is a direct result of the multiplication of the reference with the input signal within the PCC, is greater for input signal-to-noise ratios above -10dB. For input signal-to-noise ratios below -10dB the output signal-to-noise ratio asymptotically approaches a constant. This output signal-to-noise independence on input signal-to-noise is due to the combined effect limiting signal (which is mostly noise) amplitude information by the hardlimiter and the bounding of the spatial correlation by the low pass filter.

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

This dissertation describes our recent results in the study of various types of photonic switches. Special attention is given to the devices with Fabry-Perot etalon or planar waveguide structures based on dispersive optical nonlinearities. Basic optical logic functions, such as digital pattern recognition, symbolic substitution, and all-optical compare-and-exchange operation are demonstrated using ZnS and ZnSe nonlinear interference filters. Differential gain, cascading, and optical latching circuits are demonstrated using GaAs/AlGaAs multiple-quantum-well nonlinear etalons that are compatible with diode-laser sources, and the relationship between differential gain and device response time is established through a thorough investigation of the switching dynamics. Preliminary results also indicate that optical fibers can be used as interconnects between optical logic gates. Picosecond all-optical switching with good (> 3:1) contrast is demonstrated for the first time in single-mode strip-loaded GaAs/AlGaAs nonlinear directional couplers (NLDC's). The anisotropy of quantum-well structure to light polarization is used to achieve polarization-dependent two-beam switching, and the optical Stark effect is used to demonstrate all-optical modulation in an NLDC with subpicosecond recovery time.