We have observed experimentally photonic band gap in dispersion curves of SPPs excited at a 1-D dielectric lattice structure on a flat metal surface. The observation result is compared with theoretical result by using of the well-known calculation method of diffraction, rigorous coupled wave analysis method.
Photonic band gap interaction between surface plasmon (SP) and dielectric gratings is calculated by rigorous coupled wave analysis (RCWA). Results from the RCWA show that the reflectance goes down near to 0%, and the diffraction efficiency increases above 50% even though the modulation depth of the grating layer is less than 100nm. If the grating vector is twice of the wave vector of SP, on the other hand, the reflectance surprisingly increases up to 90% even though the resonance condition of the SP is satisfied. This photonic band gap effect at the SP resonance can be completely analyzed by the RCWA, and verified by experiment.