(a) Variation of reflectivity of port 1 and transmissivity of port 2 over the coupling length L when the wavelength is 1.55 μ m and l = 2 μ m (points for the transfer matrix model results; lines for the FEM results ); (b) Distribution of the absolute value of the electric field in the reflector under L of 300 nm and 750 nm when l = 2 μ m ; (c) Variation of reflectivity of port 1 and transmissivity of port 2 for l = 1 μ m and l = 3 μ m .