Design And Study Of Splitter Based On Self-Collimation In Phtonic Crystal

With the rapid development of optical communication technology,the requirements of information transmission and processing are greatly improved,which lead us to use high-performance optical devices and optical integrated products.Optical beam splitter is an important component of optical communication,and it is also a critical part of optical integration system,which is mainly divided into polarized beam splitter and optical power splitter.The performance of optical beam splitter plays an important role in the quality of optical communication.Therefore,the study of optical beam splitter has become a hot spot at home and abroad.The self-collimation effect of photonic crystals refers to the characteristics that the beam can be collimated in the structure without introducing a defect structure.The optical devices based on self-collimation have attracted people's attention because of their advantages of small size,high efficiency and adjustable structure.This thesis focuses on the study of the photonic crystal beam splitter based on the self-collimation effect,and the main achievements and conclusions are listed as follows:(1)A photonic crystal PBS with a non-orthogonal heterojunction structure is proposed,which is based on the bandgap properties and self-collimation effect of photonic crystal.In the proposed PBS structure,the beam can be self-collimated and propagate without diffraction,and the polarization separation of and transverse electric(TE)mode from transverse magnetic(TM)mode is realized at the interface.The self-collimation effect can be used to control the transmission of light in order to realize the general light guiding of the waveguide,and it can greatly reduce the difficulty in manufacturing process because of no additional defects introduced.The splitting properties,transmission properties and polarization extinction ratio of the PBS are numerically simulated and analyzed by using Rsoft software combined with the plane wave expansion method(PWM)and the two finite-difference time-domain method(2D-FDTD).It is shown that a high efficiency and a large separating angle for TE and TM modes in a wide frequency range0.275-0.285 a/? can be achieved.The transmission efficiency is above 88% for both TE and TM modes,and the extinction ratios are more than 26.57 dB for TE mode and 17.50 dB for TM mode,respectively.(2)A polarization independent 1×2 power splitter with a composite defect structure is proposed,which is based on the self-collimation effect by introducing a row of defect air hole and a defectlayer.In the proposed splitter,the light can be collimated to propagate and divided into two beams according to 1:1 proportion.The propagation properties of the power splitter are numerically simulated and studied by the PWE method and the 2D-FDTD method.The results show that in the designed 1×2 splitter,the light of TE modes and TM modes in a wide frequency range 0.160-0.187a/? can propagate along a straight line at the same time and be divided according to the beam splitting ratio of 1:1.(3)A polarization independent 1×3 power splitter with two composite defect structures is proposed,which is based on the self-collimation effect in two-dimensional photonic crystal.In the 1x 3 power splitter,the light can be collimated to propagate and divided into three beams according to 1:1:1 proportion.The propagation properties of the proposed splitter are numerically simulated and studied by the PWE method and the 2D-FDTD method.It is shown that in the designed 1×3splitter,the light of TE modes and TM modes in a wide frequency range 0.160-0.187 a/? can propagate along a straight line at the same time and be divided into 3 bunches according to the beam splitting ratio of 1:1:1.