Vertical coupling into a photonic crystal waveguide using band folding design

We propose a design for coupling light in/out of a hybrid photonic crystal surface plasmon polariton (PhC-SPP) waveguide using the band folding concept and demonstrate its feasibility. The finite-difference time-domain (FDTD) technique and rigorously coupled-wave analysis (RCWA) was used to study the absorption spectrum and dispersion diagram. By superimposing a second periodicity into the waveguide region, vertical diffraction is introduced. The proposed grating coupler couples light incident from free space directly into the PCWG modes without using any extra taper structure.