Study Of All-optical Logic Gates Based On The Self-collimation Effect Of Two-dimensional Photonic Crystals

All-optical network solves the problem of applicability of the original network node equipment,it can keep the original network structure in the case of unaffected,but also to meet the needs of ultra-high-speed network construction.During the application,it can fuse signals with different formats and interconnect different types of systems.All-optical networks are relatively scalable and transparent,and have the advantage of reconfigurability.Its reconfigurability feature can greatly enhance the flexibility of the network while improving the reliability of the network.In all-optical networks optical switches and all-optical logic gates are the basic key devices.All-optical logic gates enable identification of addresses and extraction of signals in optical communication networks,and for optical signals,logic modulation in optical transmission networks and photonic integrated circuits.The selection of materials is also very important in the study of optical switches and all-optical logic gates.Photonic crystals,as a special optical medium with periodic dielectric constant modulation,can be well applied to the design of optical switches and all-optical logic gates.The self-collimation effect is one of the unique properties of photonic crystals,which can be used to effectively control the transmission of light beams along a straight line.This has also attracted the attention of researchers in China and abroad.In this thesis,a 1×2polarization-independent all-optical optical switch is proposed through the self-collimation effect of a two-dimensional photonic crystal using the linear interference principle,and an asymmetric Mach-Zendel interferometer is proposed based on the principle of the optical switch,and five new all-optical logic gates based on the self-collimation effect of a two-dimensional photonic crystal are proposed and analyzed by applying this interferometer,as follows.(1)A 1×2 polarization-independent optical switch based on the self-collimation effect of a two-dimensional photonic crystal is proposed.The optical switch is constructed by introducing a line defect in the photonic crystal along the Γ-X direction.The conversion function of the optical switch was achieved by adjusting the radius of the line defect and controlling the initial phase of the incident light source,and the output transmitted and reflected powers were calculated.In the process of realizing the optical switch,the reflection of the beam was analyzed by deleting one row of line defects study,and the study of superimposing multiple line defects was carried out to finally determine a total reflector consisting of four rows of line defects.(2)proposed an asymmetric Mach-Zendel interferometer based on the self-collimation effect.The relationship between the incident,reflected and transmitted beams after passing through a single beam splitter in an interferometer is investigated.The relationship between the transmission peak spacing and the difference between the arm lengths of the two interferometer arms,as well as the relationship between the transmission peak frequency and the difference between the interferometer arm lengths,were analyzed.The results show that the frequency of the transmission peak is shifted toward the lower frequency as the arm length difference increases,while the peak interval decreases nonlinearly.(3)In this thesis,five new all-optical logic gates are proposed by combining the principle of optical switching with the asymmetric Mach-Zendel interferometer of two-dimensional photonic crystal,which are all-optical logic NOR,NAND,XOR,OR and AND based on the self-collimation effect of two-dimensional photonic crystal.Using the property of self-collimating transmission of light in photonic crystal,FDTD simulation is applied to obtain the field distribution and response time with certain normalized frequency,and the transmitted power of the output beam is calculated,and the logic function of each logic gate is verified by setting the threshold.The simulation analysis results show that the contrast of each logic gate is above 7d B,and the designed logic gates have small physical size and relatively fast response time within 510 fs,which has a broad prospect in the design and application of integrated optical neighborhood.