In this paper, new structures of two-dimensional periodic photonic crystals in the form of dielectric rods with different geometric shapes, are presented. All photonic crystals presented in this paper are in a square lattice. Band structure and photonic band gap limitation graph of these structures are obtained by using numerical methods of plane wave expansion (PWE) for TE and TM modes. The simulation results for these structures show different photonic band gap widths and places for different structures and modes. تفاصيل المقالة