S.E. Dissanayake, K A I L Wijewardena Gamalath, Simulation of Two Dimensional Photonic Band Gaps, ILCPA Volume 24, International Letters of Chemistry, Physics and Astronomy (Volume 24) https://www.scipress.com/ILCPA.24.58 Abstract: The plane wave expansion method was implemented in modelling and simulating the band structures of two dimensional photonic crystals with square, triangular and honeycomb lattices with circular, square and hexagonal dielectric rods and air holes. Complete band gaps were obtained for square lattice of square GaAs rods and honeycomb lattice of circular and hexagonal GaAs rods as well as triangular lattice of circular and hexagonal air holes in GaAs whereas square lattice of square or circular air holes in a dielectric medium ε = 18 gave complete band gaps. The variation of these band gaps with dielectric contrast and filling factor gave the largest gaps for all configurations for a filling fraction around 0.1.The gap maps presented indicated that TM gaps are more favoured by dielectric rods while TE gaps are favoured by air holes. The geometrical gap maps operating at telecommunication wavelength λ = 1.55 μm showed that a complete band gap can be achieved for triangular lattice with circular and hexagonal air holes in GaAs and for honeycomb lattice of circular GaAs rods. Keywords: Dielectric Contrast, Filling Fraction, GaAs, Gap Maps, Honeycomb Lattice, Lane Wave Expansion, Mode Field Distribution, Photonic Crystal, Square Lattice, Triangular Lattice