The perfectly matched layer (PML) can be used as an excellent boundary in the finite-difference time-domain method; however, it fails to absorb surface plasmon (SP) wave directly. In order to absorb an incident SP wave at the edge of a metal surface, an impedance-matching layer (IML) is implemented between the metal surface and the PML. A very low SP wave reflectance of -26.54 dB is achieved through the use of an IML with a length of only lambda/3. The IML significantly reduces SP wave reflectance and creates a quasi-infinite regime for the purpose of SP wave propagation on the metal's surface while the acquired simulation area undergoes a slight increase.
