Research of complete band gap of 2-D compound square lattice structure

With the method of plane wave expansion,the band gap structures of 2-D photonic crystal were calculated. Connecting square dielectric cylinder of silicon with the grid structure,the band gap structure of square lattice was optimized to gain bigger full band gap.After adjusting the media at the appropriate width of dielectric cylinder of silicon and the width of grid, a larger complete band gap was obtained in the compound structure of square lattice.The results show that in case of square lattice structure,only the TE mode band gap is found in the square dielectric cylinder in 0.5a width (a is the lattice constant), only the band gap of TM mode is formed in the structure of the same periodic grid in 0.22a width.In the case of compound structure,adjusting the width of w and d appropriately,when media column width is 0.5a and the grid width is 0.05a,a larger complete band gap in 0.0417ω_e could be obtained (ω_e,is center frequency).In the case of w constant,full band gap can be formed with the grid width of 0.04a～0.11a;in the case of the grid width d unchanged,full band gap can be found with the dielectric pillar width of 0.42a ～0.76a;adjusting the dielectric constant within 4 ～36,it can find different full band gaps are found with the dielectric constant of 8.41～ 36.The results are very useful to the production and application of two-dimension photonic crystal.