Research On Optical Devices Based On Woodpile Structure

Three-dimensional photonic crystal has a complete bandgap.It can realize the transmission controlled for the photon in the three-dimensional space.Therefore,three-dimensional photonic crystal has a very important application and effect in the design of optical integrated devices.In this paper,we simulated and investigated the ultra-short coupling length in off-plane directional coupler,ultra-long waveguide and the propagation of y-waveguide in woodpile structure working in microwave band by finite-difference time-domain method(FDTD)method.The main contents are as follows:First,an off-plane directional coupler is simulated and investigated in detail in the woodpile structure.The results show that the 1.9a coupling length is obtained when the rods,which are located at the coupling region,are shifted in the opposite direction.Then,the ultra-short coupling length 1.7a can also be obtained when the shifting and reducing of width for the rods are carried out simultaneously.The channel drop filter included of the 1.7a coupling length is designed and simulated.The results prove further in our investigation.Secondly,we designed,simulated and analyzed S-type waveguide,Ladder-type waveguide,Clip-type waveguide on the basis of the designed x-type waveguide.In the same size structure,the length for S-type waveguide,ladder-type waveguide and Clip-type waveguide are 53a,63.5a and 128a,respectively.Finally,the properties of the y-type waveguide,serrated-type direct waveguide are studied.The results show that the propagation characteristics of the y-type waveguide are affected by the waveguide width and position.The bandgap is shifted to the high frequency when the waveguide width is increased.And the transmission efficiency is higher when the symmetry axis is located at the center inversion symmetry axis.When the width differences between two adjacent rods in the serrated-type waveguide increase,there are two bandgaps.At the same time,the bandgap moves to lower frequency.The bend waveguides are simulated and analyzed.The results show that they can realize the well transmission.