How to find effective refractive index of 2-D photonic crystal using CST MWS

I have designed a 2-D planner photonic crystal, with Si rods in air background, offering photonic bandgap around 200THz. Using line defects, I have designed a coupled-resonator optical waveguide (CROW).

Now, I want to find the effective refractive index of the entire system for each variation of defects' radii.

I have used CST FDTD and CST frequency domain solver. Both of them are calculating the same effective refractive index, equal to one.

Can anyone suggest me what the wrong thing I am doing?

Excitation wavelength and atomic spacing must be harmonically related to satisfy Bragg's Law of diffraction.



check units of measure and exponents are correct.