We proposed a novel compact and integrated optical modulator, which consists of p-i-n silicon photonic crystals with
triangular lattice and a line defect waveguide. The device operation is based on a dynamic shift of the photonic band gap
(PBG), which is induced change in the silicon refractive index by the free carrier injection. We have numerically
analyzed and investigated its light modulation performance by using the finite-difference time-domain method. Being a
small size and high performance, the designed optical modulator can be used in photonic integrated circuits.