| Compared with one dimensional and two dimensional photonic crystals, three-dimensional photonic crystal has complete bandgap. It is means that the light can be controllably propagated along multi-directions in three-dimensional space. This characteristic is important for the design of an integrated optics. In this paper, by finite difference time domain (FDTD) method, off-plane cavity-cavity coupled waveguides, directional couplers, and space frequency selector in three-dimensional photonic crystal are designed, simulated and analyzed.First, using FDTD method, we have investigated in detail the transmission property of the cavity-to-cavity coupling waveguide and off-plane and in-plane bend-waveguide in woodpile structure. In-plane cavity-to-cavity coupled waveguide; C-type and Z-type waveguides are designed and simulated. The results show that the light can be propagated along the waveguide we designed. Then, we design an off-plane cavity-to-cavity coupled waveguide included of multi-directional transmission. The results show that this structure can realize the space transmission. This design enables us to control the transmission of light in three-dimensional space.Then, coupled wavelength adjustment in directional coupler of woodpile structure is investigated, simulated and analyzed. Two methods are considered. One change the rod width, the other is the shifting of rods. The results show that the decreasing width of rod can shorten the coupling length. An ultra-shorten coupling length can be obtained by shifting the two rods along the opposite direction, which is less than 3a.Last, we analyzed the transmission property of space frequency selector. We introduce a symmetric or non-symmetric space micro-cavity in woodpile structure. The results show that the both micro-cavity can realize frequency selective property. For the non-symmetric micro-cavity, the output frequency can be adjusted continuously when the angle between micro-cavity and input waveguide changes. |
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