We present an improved perfectly matched layer (PML) for the analysis of plasmonic structures, based on the manipulation of PML parameters. Two different types of stretched coordinate PML are employed sequentially in the spatial domain: a real stretched coordinate PML to increase the effective buffer space around plasmonic structures and a complex stretched coordinate PML to absorb outgoing waves and terminate the computational domain. Numerical examples show that a significant increase in computational efficiency is obtained because the proposed PML can be placed closer to plasmonic structures than the regular PML without affecting the field distribution of bound modes.

In the FDTD simulation of microwave circuits, a device in very small size compared with the wavelength is often handled as a lumped element, but it may still occupy more than one cell instead of a wire structure without volume routinely employed in classical extended FDTD algorithms. In this paper, two modified extended FDTD algorithms incorporating a lumped element occupying more than one cell are developed directly from the integral form of Maxwell's equations based on the assumption whether displacement current exists inside the region where a device is present. If the displacement current exists, the modified extended FDTD algorithm can be represented as a Norton equivalent current-source circuit, or otherwise as a Thevenin equivalent voltage-source circuit. These algorithms are applied in the microwave line loaded by a lumped resistor and an active antenna to illustrated the efficiency and difference of the two algorithms.