Bandstructure analysis of the woodpile PhC structure. (a) Numerically calculated band structure of the woodpile PhC with Al2O3 rods. The lower right inset depicts the first Brillouin zone of the woodpile structure. (b) The dependency of the layer-to-layer distance onto the longitudinal and transverse cut-off frequencies. The TM-like and TE-like PBGs in the transverse directions are highlighted with light green and red colored areas. (c) The PBG variations for other directions. The dashed white line indicates the upper cut-off frequencies in the Γ- X′ direction.