(color online) Plots of effective refractive indices of (a) the supermodes and 2nd order SP modes and (b) 1rt–3rd order SP modes versus wavelength for the grapheme layer filled dual-core photonic crystal polarizer; plots of effective refractive index of the even/odd mode versus wavelength for the dual-core photonic crystal (c) without and (d) with the grapheme layer. The inset is a zoom-in view showing the effective refractive index difference of x- and y-polarization mode on a log scale versus wavelength.