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Genetic algorithm optimized perfectly matched layers for finite difference frequency domain applications

The perfectly matched layer (PML) has previously been introduced by Berenger (1994) as a material absorbing boundary condition for electromagnetic waves and applied in two- and three-dimensional FDTD simulations. This PML boundary condition has been interpreted as a coordinate stretching scheme in a complex space. Chew and Jin [1995] analyzed the propagation of electromagnetic waves on a discrete PML lattice, and derived closed form expressions for the reflection coefficients from PML interfaces, Unlike for a continuous medium PML, the reflection from a discrete medium PML interface coefficient does not vanish for all frequencies and angles. In this paper, the parameters defining a multilayer discrete PML medium terminated by a conducting plane are optimized to minimize the absorber's reflection coefficient over a specified range of frequencies and incident angles. This optimization is performed using a genetic algorithm and results in profiles quite different from the commonly used linear and quadratic ones.