Study Of Optical Components In Three-Dimensional Photonic Crystal

The light wave can be controlled by photonic crystal, which is the foundation of all-optical integration and photoelectric integration. The light can be propagated in three-dimensional space in three-dimensional photonic crystals due to the existence of complete bandgap, so it is very necessary to study three-dimensional photonic crystal devices. Waveguides, channel drop filter and directional coupler are important devices in photonic integrated circuits and optical communication field. The transmission spectra and field distributions in waveguides, channel drop filters and directional coupler of three-dimensional photonic crystals are simulated using finite difference time domain method. The main work is as follows:Firstly, the transmission properties of waveguides in2D+3D hetero-structure are considered. A like-sandwich structure, which include one two-dimensional square lattice photonic crystal and two woodpile structures, is designed. In this structure, we introduce a45°and90°waveguide bends in two-dimensional part. In order to improve the transmission, many methods have been considered, such as perturbation. The results show that the transmission can be increased by perturbation optimization for45°waveguide bend. While smoothing design for bend location and the reducing for period of rods on both sides of waveguide can improve effectively the transmission in90°waveguides.Then, a new structure, which is composed of slabs of two-dimensional triangular lattice air-holes and dielectric-rods, is constructed and simulated. The results show that the structure has a good complete bandgap. It is known that the bandgap can be controlled by many parameters, such as filling factor, dielectric constant, and lattice type. We consider the moving bandgap when the parameters are changed. The simulations show that the section of rods can adjust effectively the bandgap. At the same time, the bandgap will move to higher frequency as the filling factor decreased.Meanwhile, we introduce metallic materials in woodpile structure. The transmission spectra are simulated by finite difference time domain method. The results show that there is a complete bandgap for woodpile structure composed of metallic rods. But the bandgap move to a high frequency. This is due to the cut-off frequency of metallic material.Next, a plannar channel drop filter with four-port is designed, analyzed and theoretically simulated in the hetero-woodpile-structure. The structure includes three parts, namely along the propagation direction, the lattice constant in the core woodpile is different from two cladding woodpiles. This channel drop filter is comprised of two straight waveguides separated by an air-cavity system in the same layer. Through simulations, we found that adjustment of the resonant modes can be achieved in various ways, such as changing cavity size, lattice constant and distance between cavities. The results also show that this structure can realize the energy transfer between bus and drop waveguides.Last, off-plane directional coupler in three-dimensional photonic crystal is designed and simulated. By the transmission and field distribution, the coupling lengths for different frequencies are given. When the structural parameters are adjusted, the coupling length can be shortened for a same frequency. At the same time, power splitter and wavelength division multiplexer based on this directional coupler are designed. They also realize a high transmission.