Phase shifts and interference in surface plasmon polariton waves

A pi phase shift between the incident wave and surface plasmon polariton (SPP) waves launched from a one-dimensional (slit or groove) subwavelength structure has been found in numerical simulations and invoked to explain recent measurements of optical transmission in slit arrays. Although groove launchers exhibit an overall phase shift that depends on the groove depth, it is shown here how magnetic field induction at the incident surface, and oscillating dipoles from the accumulated charge at the slit or groove edges on the entrance facet lead to an intrinsic p phase shift, independent of the groove or slit depth. Destructive interference between the p-shifted surface wave and the incident wave explains the observed transmission minima when the pitch of an array of slits becomes equal to an integer multiple of the SPP wavelength. (c) 2008 Optical Society of America.