Giant transmission Goos-Hanchen shift in surface plasmon polaritons excitation and its physical origin

Excitation of surface plasmon polaritons (SPPs) propagating at the interface between a dielectric medium and a silver thin film by a focused Gaussian beam in a classical Kretschmann prism setup is studied theoretically. We find that the center of the transmitted Gaussian evanescent wave has a giant lateral shift relative to the incident Gaussian beam center for a wide range of incident angle and Gaussian beam wavelength to excite SPPs, which can be more than two orders of magnitude larger than the silver film thickness. The phenomenon is closely related with the conventional Goos-Hanchen effect for total internal reflection of light beam, and it is called the transmission Goos-Hanchen shift. We find that this lateral shift depends heavily on the excitation wavelength, incident angle, and the silver layer thickness. Finite-difference time-domain simulations show that this transmission Goos-Hanchen shift is induced by a unique dynamical process of excitation, transport, and leakage of SPPs.