Investigation of optical properties of one-dimensional photonic crystals by coupled mode theory

Due to existence of photonic bandgap in photonic crystals, the propagation of light wave is restricted, which has opened the enormous area to design and fabricate the efficient photonic devices for advanced communication systems. This article reports the simulated investigation of optical parameters of one-dimensional photonic crystals (1DPCs) by using pertinent concept of coupled mode theory (CMT). The result reveals that the forward and backward electric field amplitude exponentially decrease inside the grating along x-direction, which is due to the imaginary term involved in wavevector. The forward and backward field intensity shows the oscillatory behavior in a photonic device. The oscillation occurs due to variation in group velocity of photons in reflectors. The group velocity dependence on frequency has been unveiled, it has been observed that group velocity vanishes at the forbidden band edges i.e. 0.389 and 0.681, while it becomes superluminal from 0.521 to 0.532. The group velocity becomes superluminal inside the photonic bandgap due to the evanescent photons.