Effects of Disorder on Group Velocity in One-Dimensional Photonic Crystals

Effects of thickness disorder on the superluminal group velocity within photonic band gaps and the ultralow group velocity of defect modes in one-dimensional photonic crystals are studied theoretically. It is found that the introduction of thickness disorder leads to a decrement in group velocity of the superluminal modes and an increase in group velocity of the ultraslow modes. Both superluminal and ultraslow modes at higher photonic band gaps are highly affected by thickness disorder. For the superluminal and ultraslow modes at the first photonic band gap, their group velocities are nearly unchanged with thickness disorder.