Research On Optical Beam Splitter And All-optical Encoder Based On Two-dimensional Photonic Crystals

With the maturation of Internet technology,the information service provided by traditional communication network has been unable to cope with the phenomenon of sudden increase of information.Therefore,all optical network emerges with the advantages of long relay distance,large information capacity,fast transmission speed and low loss.The quality of all optical network depends on the performance of optical information processing devices.As the key components of optical information processing devices,optical beam splitter and all-optical encoder have become the focus of research.In recent years,photonic crystals,with their small size,easy to control the direction of light propagation and simple structure,have important application value in the field of photonic device design.Based on the photonic band gap characteristics and photonic local characteristics of photonic crystals,this paper focuses on optical beam splitters and all-optical encoders.The specific work is as follows:(1)Based on the photonic band gap and photonic local characteristics of photonic crystals,three kinds of photonic crystal Y-type 1×2 equal beam splitters and a photonic crystal 1×4 beam splitter with microcavity are proposed.Using Rsoft software,combined with the plane wave expansion method and the finite difference time domain method,four kinds of beam splitters are simulated and studied.The results show that based on photonic crystal Y-type 1×2 equal beam splitter,When a point defect dielectric column with a radius of 0.26 a is added to the connection between the input waveguide and the V-type waveguide,the transmittance of the two output ports is 47.54%,and the total transmittance is 95.08%;When the radius of the dielectric column at the V-type waveguide branch is adjusted to 0.09 a,the transmittance of the two output ports is 48.66%,and the total transmittance is 97.32%;When the microcavity is added to the connection between the input waveguide and the V-type waveguide,the transmittance of the two output ports is 49.58%,and the total transmittance is 99.16%;A 1×4 beam splitter was proposed based on a 1×2 beam splitter with a microcavity.When the radius of the point defect dielectric column at the corner is 0.157 a,the beam splitting ratio of 1:1:1:1 can be achieved,and the total transmittance is 97.68%.When the radius of the point defect dielectric column at the corner is 0.199 a,the beam splitting ratio of2:2:1:1 can be achieved,and the total transmittance is 99.22%.(2)Based on the photonic band gap and photonic local characteristics of photonic crystals,a photonic crystal all-optical 4×2 encoder with microcavity and a photonic crystal all-optical 4×2broadband encoder are proposed.Using Rsoft software,combined with the plane wave expansion method and the finite difference time domain method,two kinds of encoders are simulated and studied.The results show that the all-optical 4×2 encoder with microcavity based on photonic crystal has a working wavelength of 1.55μm,a contrast ratio of up to 24.55 d B and a response time of less than 1.11ps;the all-optical 4×2 broadband encoder based on photonic crystal has an operating wavelength range of 1.536-1.560μm,covering most of the C-band(1.530-1.565μm),the contrast range is 14.43-28.94 d B,and the response time does not exceed 0.97 ps,when the working wavelength is 1.55μm,the contrast ratio reaches the maximum value of 28.94 d B.The proposed photonic crystal beam splitter has the characteristics of simple structure,small size and low loss;the photonic crystal all-optical encoder has the characteristics of easy integration,high contrast and fast response speed.Both of these photonic devices can have broad application prospects in the fields of optical communication systems and integrated optical circuits.