Photonic crystals(PCs)

also known as photonic band-gap materials

are artificial dielectric or metallic structures in which the refractive index modulation gives rise to stop bands for electromagnetic waves(EM) within a certain frequency range.The discovery of photonic crystals has opened up a promising tool to control the flow of light.A very interesting feature of light guided through photonic crystals is that the group velocity of the light may be reduced by orders of magnitude.There are several devices taking advantage of this property both in PC waveguides and in extended photonic crystal lattices.The excellent optical properties of PCs come from their special band structures.The band structures can be associated with the type of lattice that photonic crystals take on.Up to the present

many works have been devoted to study the properties of PCs which have hexagon

square and honeycomb lattices.The two dimensional Suzuki-phase lattice is the novel one

which firstly was brought forward in the context of sound propagation by sonic crystals and afterward its equivalent was introduced for photonic crystals.In this paper a complete research of the photonic band structure for Suzuki-phase lattice is presented

including the periodic array of air holes in a dielectric background and the periodic array of dielectric rods in air.With the help of plane wave expansion method

the impacts of scatter element radius and refractive index was investigated.The results demonstrate that the band-gaps are mostly for TM mode in the periodic array of air holes in a dielectric background

but the TEmode in the perio-dic array of dielectric rods in air.The complete band-gap presents itself in all type photonic crystals only when refractive index of the medium is larger enough.When refractive index is smaller

the complete band-gap doesn't emerge.For the periodic array of air holes in a dielectric background

the results demonstrate that in some rang of air hole radius the fifth and sixth bands are separated from each other distinctly.The dispersive curves for fifth band along Г-

X

1

direction and sixth band along

X

1

-

M

direction are very flat

implying group velocity equal to zero.The modal field profiles were also calculated.From these results

we can find the fifth and sixth bands are mini-bands created by the coupling of defect modes.This phenomenon

which can be used for slow light engineering in photonic crystals

has not been found in the periodic array of dielectric rods in air and other lattices.