Research On All-optical Adder Based On Two-dimensional Photonic Crystal Logic Gates

With the rapid development of Internet technology,people's requirements for information capacity and transmission speed are increasing,and the performance of electronic devices is gradually facing bottlenecks.Compared with the traditional electronic technology,all-optical network has more advantages in information capacity and data transmission rate.Using photons instead of electrons can effectively solve the problem of mutual interference between electrons and improve the transmission rate and anti-interference ability of devices.As one of the all-optical network devices,photonic crystal logic devices(PCL)have attracted more and more attention because of its low transmission loss,narrow resonance spectrum,small size and easy integration.PCL has potential applications in new integrated optics and all-optical communication networks.This paper mainly focuses on the coupling characteristics of two-dimensional photonic crystal ring resonator and microcavity,studies and analyzes the all-optical logic gate and adder technology of photonic crystal using the principle of linear interference,and optimizes its structure to reduce the size of components and improve the performance of devices.The main research contents of this paper include:(1)By using the plane wave expansion method and the finite-difference time-domain method,the energy band structure of the photonic crystal with square lattice structure,the coupling characteristics and transmission law of the ring resonator and the micro cavity are studied and analyzed,and the influence law is summarized.The results show that when the size of the medium cylinder outside the micro cavity remains unchanged,the coupling resonance peak of the ring resonator and the micro cavity will increase with the increase of the radius of the medium cylinder inside the micro cavity When the radius of the external medium increases,the coupling resonance peak will move to the high frequency direction.(2)An eight channel photonic crystal wavelength division multiplexer is designed by using the coupling law of the ring resonator and the microcavity and controlling the size of the central and external dielectric columns of the microcavity.The device consists of four ring resonators,each of which corresponds to two microcavities.The structure of the device is optimized and verified by simulation to improve its transmission characteristics.The device has the advantages of small size,only 23 ?m×18 ?m,high transmission efficiency,over 97%,convenient control,easy integration and good frequency selection characteristics.(3)Based on the linear interference effect,a design method of all-optical logic gate of two-dimensional photonic crystal is proposed.By introducing the optical path difference into the ring cavity,the corresponding phase difference is produced,which leads to theinterference or cancellation of the optical wave.Combined with the coupling law of the ring resonator and the micro cavity,the optical logic gates of or,and,XOR,non,or non and non are realized.The parameters of the proposed logic gates are optimized and simulated,and the appropriate central medium of the micro cavity is selected Column radius,to improve the transmission efficiency and performance of logic gate,the contrast of each logic device is high,above 7.3dB,and the device size is small,the maximum is 21.5 ?m×20.5 ?m and the time transmission response is fast,all within 218 fs.(3)On the basis of the designed logic gate,the structure design method of all-optical half adder and full adder is proposed through the cascade coupling of multiple logic gates.By using the plane wave expansion method and the finite-difference time-domain method,the parameters of the center dielectric cylinder radius of half adder and full adder are optimized to reduce the transmission loss of light wave in the ring resonator and micro cavity,and further Improve the output rate of the device.Through simulation and verification,the results show that the designed device not only has small physical size,but also has high transmittance,contrast and fast response period,all of which are within 344 fs.It has potential application prospects in the field of integrated optics.