Separation of surface plasmon polariton from nonconfined cylindrical wave launched from single slits

We theoretically investigate the separation positions of surface plasmon polariton (SPP) from the cylindrical nonconfined diffracted light launched from a single slit. Through an analysis of the finite difference time domain calculations and the analytical solution of a line source on a metal surface, we find the wavelength dependent SPP separation positions defined as the lateral distance from the slit with two different criteria. These results show that the SPP separation positions can be approximated by a simple relationship given by the permittivity of the metal and by the wavelength regardless of how the criteria are chosen.