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Numerical Design and Demonstration of the Feasibility of an All-Optical 4-Bit Adder Composed of Nonlinear Fabry-Perot Cavities
Jennifer E. Houle, Dennis Sullivan, Ata Zadehgol and Mark G. Kuzyk
This work demonstrates how one would make a 4-bit adder comprised of nonlinear Fabry-Perot cavities using models of each unit as well as modeling the network of units. In the process, we identify challenges and how they can be resolved. Each Fabry-Perot device is composed of two reflectors, which we model as silver mirrors on either side of a cavity that holds a nonlinear Kerr material. We show how these devices are optically bistable and suitable for fast logic operations on the order of picoseconds. However, issues that are generally not appreciated such as signal degradation due to other nonlinear processes are treated, and methods to circumvent them are discussed. Part of the solution is to reject light from these other processes through filtering and using an amplifying buffer between devices to boost the transmitted signal’s amplitude to the desired value as well as to provide control for logic operations. This work uses the method of finite-difference time-domain (FDTD) in one-dimensional (1D) space to demonstrate the feasibility of the proposed idea, which has the advantage of treating all processes numerically without the need for approximations that might be invalid in such devices. The demonstration of the 4-bit adder shows that this interconnected multi-component system is robust and does not suffer from instabilities, which are suppressed by the combination of filtering, amplification and buffering.
Keywords: Nonlinear optics, optical logic gates, Fabry-Perot interferometer, optical Kerr effect, optical bistability