Time-domain Method In Cylindrical Coordinates Research Articles

A Perfectly-Matched Layer Formulation Capable of Absorbing Multi-Modal Waves in Cylindrical FDTD

The perfectly-matched-layer (PML) absorbing boundary condition as applied to the finite-difference time-domain method in cylindrical coordinates is investigated. A critical error in implementing coordinate stretching which is present in various published works is identified and shown to diminish wave absorption efficiency for all wave modes except rotationally invariant ones. A correction to the underlying coordinate stretching formulation is proposed and confirmed to improve wave absorption by approximately two orders of magnitude for higher cylindrical wave modes even when the PML absorber is placed within the near-field region to the axis of rotation.

Investigation of image magnification properties of hyperlenses formed by a tapered array of metallic wires using a spatially dispersive finite-difference time-domain method in cylindrical coordinates

In this paper, the spatially dispersive finite-difference time-domain (FDTD) method in cylindrical coordinates is applied to model the hyperlenses formed by a tapered array of metallic wires. The hyperlens device is modeled using the effective medium theory as a frequency and spatially dispersive dielectric. The gradual increase in spacing between wires along the radial direction of the physical structure is represented by the reduction of plasma frequency of the effective medium. Simulation results show that the image transfer and magnification capability of the hyperlens is insensitive to its transverse dimension. A seven-fold magnification of a subwavelength source distribution transferred to a distance of three wavelengths is demonstrated using a hyperlens with high plasma frequency at its front interface.