Study Of Polarization Independent Photonic Devices Based On Self-collimation In Phtonic Crystal

With the rapid development of the computer technology and the optical communication technology,network data traffic has shown explosive growth.However,the currently available bandwidth is far from meeting the demand,so it is urgent to develop the all-optical network which can realize large capacity,high speed and long-distance transmission.The development of all-optical communication networks is related to optical signal processing devices.Optical switches and alloptical logic gates,as important components of optical signal processing devices,have become the focus of current research.Photonic crystals are periodic dielectric structures.Because of the unique characteristics of photonic band gap,photon localization and self-collimation effect,photonic crystals have been widely concerned by researchers at home and abroad.Based on self-collimation in photonic crystal,a polarization independent 1×2 routing switch and a polarization independent AND gate is proposed and designed in this thesis.The specific research contents are as follows:(1)A polarization independent 1×2 routing switch based on the self-collimation effect and interference theory in two-dimensional photonic crystal is proposed.The function of polarization independent routing switch can be realized by adjusting the phase difference between the signal light and the control light to achieve constructive or destructive interference.The proposed device is theoretically analyzed and numerically investigated by using PWE and finite-difference time-domain FDTD in Rsoft software.The results show that the designed switch can realize the function of 1×2 polarization independent routing switch in a wide frequency range 0.16?0.181a/?,the extinction ratios are more than 7.2 d B for transverse electric(TE)mode and 9.4d B for transverse magnetic(TM)mode,and the steady times are lower than 1ps for both TE mode and TM mode.(2)A polarization independent AND gate based on the self-collimation effect,interference theory and nonlinear Kerr effect in two-dimensional photonic crystal is proposed.In this scheme,two line defects are introduced in the self-collimation two-dimensional photonic crystal,one of which is composed of defect air holes,and the other one is composed of point defects filled with a non-linear polymer material.The two signal lights achieve constructive interference at the first line defect by adjusting the phase difference between the two signal lights,after which the Kerr effect of the nonlinear polymer material occurs at the second line defect.The refractive index changes by the optical power,and the transmittance changes accordingly.As the result,the function of polarization independent AND gate can be realized.The results show that the designed AND gate works in a wide frequency range 0.16?0.180a/?,the extinction ratios are more than 6.48 d B for TE mode and 6.86 d B for TM mode,and the steady times are lower than 1ps for both TE mode and TM mode.