Theoretical analysis of optimum parameters for woodpile-type photonic crystals

In order to optimize the structure parameters of 3-D woodpile-type photonic crystals,based on the plane-wave method,the property of complete forbidden bands of woodpile structure was theoretically studied in terms of varying aspect heightto -pitch ratios,filling fractions,and rotation angles. It was found that the gap to midgap ratio changed slightly with a filling fraction ranging from 0.25 to 0.30. The optimum height-to-pitch ratio was about 1.3. The gap to midgap ratio became larger than 0.18 when the rotation angle changed from 40° to 50° and the maximum gap to midgap ratio of 0.2 remained unchanged for the rotation angle ranging from 42° to 48° with height-to-pitch ratio of 1.3. The results show this type of woodpile structure can produce big band gaps in a wider parameter range,which offers convenience for preparing three- dimension photonic crystals in laboratory.