Optimization and tolerancing of nonlinear Fabry Perot etalons for optical computing systems.

Abstract

Since the discovery of optical bistability a considerable amount of research activity has been aimed toward the realization of general-purpose all-optical computers. The basic premise for most of this work is the widely held notion that a reliable optical switch can be fabricated from a piece of optically bistable material. To date only a very small number of published articles have addressed the subject of the engineering issues (that is, the optimization and tolerancing) of these optical switches. This dissertation is a systematic treatment of these issues. From the starting point of Maxwell's equations a simple model of optically bistable Fabry-Perot etalons is outlined, in which the material is assumed to be a pure Kerr medium having linear absorption. This model allows for a relatively straightforward optical switch optimization procedure. The procedure is applicable for optimizing any number of switch parameters. The emphasis in this dissertation is on the optimization of the contrast of the switch's output signals, with the other parameters (switching energy, tolerance sensitivity) assuming a secondary yet critical role. Following the optimization of the optical switch is a tolerance analysis which addresses the manufacturability and noise immunity of the optimized switch. In the first part of this analysis equations describing the propagation of errors through a large scale system of like devices are derived from the truth tables of the switches themselves. From these equations worst case tolerances are established on the optical switch's transfer function parameters. In the second part of the tolerance analysis the bistability model is used to arrive at tolerances on the physical parameters of the switch. These tolerances are what determine the manufacturability of the optical switches. The major conclusion of the dissertation is that, within the range of validity of the model and the other simplifying assumptions, optically bistable Fabry-Perot etalons cannot be used reliably as logic gates in large-scale computing systems.