Implementation of higher order CNAD CFS-PML for truncating unmagnetised plasma

An unconditionally stable implementation of the higher order complex frequency-shifted (CFS) perfectly matched layer (PML) is proposed for the Crank-Nicolson-approximate-decoupling (CNAD) finite-difference time-domain (FDTD) scheme. The proposed higher order CFS-PML, which is implemented by the auxiliary differential equation (ADE) method, not only has better performance than the first-order PML but also maintains the unconditional stability of the origin Crank-Nicolson (CN) algorithm. The unmagnetised plasma, which can be expressed by the Drude medium and implemented by the piecewise linear recursive convolution (PLRC) method, is truncated by the proposed PML scheme. A numerical example is provided to validate the effectiveness of the proposed formulations.