Research of composite wide band gap of 2-D photonic crystal

In order to study the characteristics of 2-D photonic crystal constructed with two different medium rods,a triangular lattice photonic crystal constructed with layer medium rods/bottom medium and air rods/bottom medium was studied.By means of finite difference time domain method the curves of transmission coefficients versus incident frequencies under different conditions were obtained.The calculated results showed that a wide gap from low to high frequency appeared in the composite photonic crystal,so the electromagnetic wave could be prohibited in a wide frequency range.The further study showed the width of band gap was influenced by the external radius of layer medium rods,while defect mode in the band gap was greatly influenced by the internal radius,dielectric constant and middle layer's dielectric constant.In fact,it is possible to produce very narrow-band optical filters and switches by regulating the photonic crystal structure parameters.