Research Of Photonic Crystal All-optical Diode

In recent years, photonic crystal as a new type of artificial materials has attracted more and more researchers’ s attentions all over the world due to its peculiar advantages and unparalleled potential applications.This paper focusses on the investigation of the photonic bandgap,photonic localization,the nonlinear Kerr effect and the optical bistable,and focusses on these characteristics apply to the all-optical diode that in order to achieve high transmittance, high contrast and high bandwidth.The specific research contents and conclusions of this paper include the following aspects:Firstly, we briefly introduce the concept of photonic crystal, the classification of photonic crystal and the fabrication methods of photonic crystal.Secondly, we use Maxwell equations to produce electromagnetic field expressions which consistence with the characteristic of photonic crystal,and some calculation methods of photonic crystal band gap are obtained. This paper focuses on finite difference time domain method(FDTD).Discussing the Yee’s grid,the numeric stability and boundary condition of FDTD method.Thirdly,we introduce a suitable photonic crystal direct coupled cavity C1 and a photonic crystal side edge coupled cavity C2,forms the Fano transmission spectrum type structure by adjusting the distance between the two cavities;and we introduce Kerr nonlinear for the cavities,then we use FDTD method to simulate the all-optical diode and analysis of the result,Our research shows that only using single signal light is difficult to achieve high positive transmittance, high contrast and large bandwidth demands(The highest positive transmission rate is only 13%, contrast is only 8).Finally,In order to overcome this difficulty, we propose a new method:The nonlinear optical bistable state of the two microcavities can be intensively tailored with the assistance of ultrashort pulse pump,a high-performance optical diode is realized with high unidirectional transmission rate and high contrast ratio for a broad operating bandwidth,and explains how it works.By using this method, we propose two implementations:(1)we add appropriate power of the pulse to the side of the nonlinear photonic cyrstal and analysis of theresults,we can achieve negative high transmittance(65.676%), positive low transmittance(0.139%)(right high and left low), and the effect of the contrast of 472;(2)we use two ultrashort pulse to pump the PC directly-coupled microcavity and the side-coupled microcavity respectively,We found that:(a) When the signal light power is 0.005 W, The ultrashort pulse1 and pulse2 power were adjusted to 18 W and 8 W, a high-performance optical diode is realized with high positive transmission rate(over 88%,which is 18% higher than the reported results) and high contrast ratio(over 83) for a broad operating bandwidth more than 0.44nm(which is tens times bigger than the reported one).(2) When the signal light power is 0.005 W, The ultrashort pulse1 and pulse2 power were adjusted to 20 W and 9 W, a high-performance optical diode is realized with high negative transmission rate(over 90%,which is 20% higher than the reported results) and high contrast ratio(over 75) for a broad operating bandwidth more than 0.4nm(which is tens times bigger than the reported one).These methods and results have important application prospects in the future optical communication and optical computing.