High order plasmonic Bragg reflection in the metal-insulator-metal waveguide Bragg grating

High order plasmonic Bragg reflection in the metal-insulatormetal (MIM) waveguide Bragg grating (WBG) and its applications are proposed and demonstrated numerically. With the effective index method and the standard transfer matrix method, we reveal that there exist high order plasmonic Bragg reflections in MIM WBG and corresponding Bragg wavelengths can be obtained. Contrary to the high order Bragg wavelengths in the case of the conventional dielectric slab waveguide, the results of the MIM WBG exhibit red shifts of tens of nanometers. We also propose a method to design a MIM WBG to have high order plasmonic Bragg reflection at a desired wavelength. The MIM WBG operating in visible spectral regime, which requires quite accurate fabrication process with grating period of 100 to 200 nm for the fundamental Bragg reflection, can be implemented by using the higher order plasmonic Bragg reflection with grating period of 400 to 600 nm . It is shown that the higher order plasmonic Bragg reflection can be em ployed to implement a narrow reflection bandwidth as well. We also address the dependence of the filling factor upon the bandgap and discuss the quarter-wave stack condition and the second bandgap closing.