基于光子晶体平板传导共振模的低功率光开关

利用严格耦合波算法计算了二维光子晶体平板结构随角度变化透过谱和波长变化透过谱,研究了透过谱上传导共振峰与二维光子晶体平板能带结构的关系。利用共振传导模的低透过和高Q值的特点,设计了基于磷化铟材料的工作在1550nm波长附近的角度分辨和波长分辨的光子晶体光开关。理论模拟结果表明,该结构透过谱上传导共振峰品质因子可达105,非线性折射率变化为10-4即可实现开关对比度接近100%。当信号光或泵浦光分别与光子晶体平板传导共振模耦合时,由于共振耦合使得泵浦光场增强,需要泵浦能量仅为184fJ,为目前所知能量最低的光开关。     

掺铒光纤布拉格光栅F-P腔的光学双稳态特性的研究

正光学双稳态是指光学系统中在一定的输入范围内对给定的输入存在着两种可能的输出状态,并且这两种状态必须可以互相转换,其输出光强和输入光强的关系表现了明显的滞后回线。光学双稳态的必要条件是系统同时具有光学非线性和反馈机制两个因素。利用光纤光栅的反射特性与非线性共同作用,会导致光学双稳态的产生、由于双稳态系统可以实现光学限幅,光学微分放大、转换开关、逻辑门、存储元件以及具有极快和可控作用功能的其他元件,因此光学双稳态系统在光计算、光通信和集成光学中具有重要的应用、用掺饵光纤连接两个相同的FBG,形成EDF-FBG腔的结构、由于光纤光栅的反射特性和掺铒光纤较大的非线性系数,会导致光学双稳态的产生、通过光栅耦合模理论和传输矩阵理论,得到光纤光栅EDF-FBG腔的透射率,最后对EDF-FBG腔的双稳特性进行了数值模拟。通过优化光栅的各个参数,发现在考虑吸收情况下仍可得低达13 mW左右的临界输入光强、理论模拟有助于选择合适的EDF-FBG腔参数达到对光栅的双稳态性能进行优化的目的。     

圆柱形微带,耦合线的色散特性分析

本文利用一种全波分析方法－－柱面坐标中的二维时域有限差分法，数值模拟了圆柱形均匀微带线和耦合线的色散特性。讨论了柱面坐标二维时域有限差分（ＦＤ－ＦＤ）法的基本理论和处理方法，并给出不同带宽的圆柱形微线和不同耦合宽度与耦合间隙的圆柱形合线的色散特性。这些结果对微波与毫米波集成电路过渡区的设计是有价值的。     

椭圆介质柱光子晶体导模区域的调控

利用时域有限差分方法,理论研究了由介电常数为8.9的介质柱排列在空气背景中组成的二维正方晶格光子晶体耦合腔光波导的传输特性.理论模拟结果表明,将微腔紧邻的两个圆形介质柱改变为椭圆形.通过改变椭圆的旋转角度能够调控导模的频率范围.通过将相邻微腔两边的椭圆形设置为不同旋转角度,可以在保证高传输效率的同时进一步地降低导模的群...     

Bragg光纤光栅的非线性开关特性研究

从耦合模理论出发,通过单独改变入射波中心波长、光纤光栅长度及耦合系数,数值研究了光纤光栅双稳态开关特性,给出了输入输出特性与这些参数的单一依赖关系曲线,得出一些有意义的结论.在此基础上,对如何减小非线性开关阈值进行了总结和探讨,并提出运用稀土掺杂光纤光栅与F-P腔相结合的结构来降低光开关阈值.     

环型谐振器非线性开关特性研究

采用耦合模理论，推导了环型谐振器的传输函数，分析了环型腔内功率的谐振加强特性，并在推导的非线性环型谐振器开关曲线的具体表达式基础上，指出损耗和耦合系数对开关特性的影响，数值模拟了非线性环型谐振器对不同输入功率Gauss脉冲的开关特性。     

二维光子晶体多模波导与单模波导的匹配传输

用多模干涉理论研究了二维正方晶格的光子晶体多模波导的3个偶模之间的干涉和自映像现象,发现它们之间的干涉可以认为是两两相互干涉叠加的结果.以7模光子晶体波导为例进行模拟计算,根据其波导的能带结构,发现在入射波的归一化频率为0.35时,3个偶模相互干涉形成的单重像在某一点重合,在这一点再连接一个单模光子晶体波导,实现了光子晶体多模波导到单模波导的匹配传输.利用有限时域差分法进行了数值模拟验证,模拟结果表明:实现了光子晶体多模波导到单模波导的高效匹配传输,传输效率达到95%.     

光子晶体波导定向耦合功分器的设计

将相互耦合的3平行光子晶体单模波导看成一个多模干涉系统,通过研究二维正方晶格光子晶体波导多模干涉的自映像效应,优化设计了一种新型1×2光子晶体波导定向耦合分束器,采用时域有限差分法对其传输特性进行模拟分析。设计过程中,根据多模干涉耦合区中周期出现的双重像的位置确定两个单模输出波导的位置,通过改变输出波导和耦合区连结的一个介质柱位置构成波导微腔结构,改变耦合区中的模场分布,实现模式匹配,从而明显减小分束器的反射损耗。计算结果表明,移动介质柱距离输出单模波导和多模波导连结处1.85a位置处时,对于波长为1.55μm的入射光,该分束器的透射率可高达99.04%。     

五平行光子晶体多模波导的耦合特性及应用

本文通过模拟计算研究了二维三角形光子晶体波导自成像多模干涉的耦合特性。提出一种二维光子2端口晶体分束器,基于自成像多模干涉效应,用有限时域差分法数值计算和分析了这种分束器的特性。研究发现这种分束器的反射率低于10-4,透射率可高达0.9999。我们分析发现造成这种现象的物理原因是多模干涉区的自成像效应,这种多模干涉在光子晶体光学集成电路中具有重大的潜在应用价值。     

基于自成像多模干涉的光子晶体波导1×2分束器

通过模拟计算研究了二维三角形光子晶体波导自成像多模干涉的耦合特性,提出了一种二维光子晶体1×2分束器。基于自成像多模干涉效应,用有限时域差分法对这种分束器的特性进行了数值计算和分析。研究发现,这种分束器的透射率可高达96%,造成这种现象的物理原因是多模干涉区的自成像效应,这种多模干涉在光子晶体光学集成电路中具有重大的潜在应用价值。     

Optical bistability and all-optical switching in novel waveguidejunctions with localized optical nonlinearity

We propose novel all-optical guided-wave devices using the structure with localized third-order optical nonlinearity where only a selected part of a waveguide both in a cross section and along a propagation direction is made from a Kerr-like nonlinear material and the rest are made from linear ones. Optical bistable devices and all-optical switching devices are realizable by utilizing bistable like nonlinear dispersion characteristics in selectively nonlinear guided-wave systems. Optical bistability and all-optical switching characteristics are analyzed in waveguide Y-junctions adopted the scheme by using a modified BPM combined with the normal mode analysis. The method to realize the guided-wave structure with localized nonlinearity is also discussed     

Bistabilities of Birefringent Vertical-Cavity Semiconductor Optical Amplifiers With Antiresonant Reflecting Optical Waveguide

Bistable characteristics of birefringent antiresonant reflecting-optical-waveguide (ARROW) vertical-cavity semiconductor optical amplifiers (VCSOA) under external optical injection with multi-mode profile and arbitrary polarization orientation are investigated theoretically. It is found that the presence of ARROW can realize stable single-mode bistable switching in VCSOAs. Furthermore, with suitable design of the bias current profile, it can be shown that ARROW VCSOAs with a large core diameter (i.e., ${ge 50}~mu{hbox {m}}$) can sustain stable single-mode bistable switching.      

切趾型非线性布拉格光纤光栅双稳开关及动态特性的理论研究

基于耦合模方程,利用含有时间推移变量的传输矩阵方法对非线性布拉格光栅(NLBG)双稳特性进行了理论分析,结果表明:在稳态情况下,不同切趾参数对NLBG双稳开关的阈值影响不同,并且正负切趾具有明显的光隔离器特点。考虑连续波输入,NLBG表现出的双稳开关特性在动态情形下极易出现一定周期性的自脉动,而且当输入光强增大到临界光强,输出可由自脉动转变为混沌状态;考虑切趾参数一定时,耦合系数的增大会导致脉动基座宽度和频率减小,当耦合系数达到一定数值后,输出状态将转变为弛豫衰减振荡。     

All-optical flip-flop operations in a coupled element bistabledevice

An optical bistable device composed of coupled nonlinear elements is proposed. This device features optical bistability without hysteresis. It is shown theoretically that a set-reset type (S-R) flip-flop operation can be easily achieved on an all-optical basis by utilising nonhysteretic bistable characteristics     

Optical bistability in a nonlinear directional coupler

In the nonlinear directional coupler, the optical field and the nonlinear material usually interact in a spatially and temporally local fashion and the device exhibits a nonlinear transmission characteristics, but it is not bistable. In this paper, it is shown theoretically that optical bistability in the input optical power is possible for the nonlinear directional coupler if the local phase change of the optical mode propagating through tile coupler is influenced by the excitation over the whole coupler. This condition can be satisfied in a coupler based on biased-pin-diodes comprising coupled asymmetric quantum wells in the i-region, Calculations show that in this configuration, the nonlinear directional coupler can exhibit sharp switching characteristics, low switching optical powers, optical bistability or bifurcation     

线性啁啾型光纤光栅双稳特性的理论研究

基于非线性耦合模理论,利用逆向递推传输矩阵方法,数值研究分析了线性啁啾型光纤光栅（LC-NLBG）的双稳开关性能。研究结果表明：在NLBG中引入啁啾能扩大实现双稳的入射光波长范围,当光栅啁啾参量发生变化时,光栅双稳开关性能表现出明显的差异,此差异源于啁啾光栅内部前向波能量分布的不同。     

Femtojoule bistable optical switching of inhomogeneously pumped laser diode at 500 MHz using mode-locked tunable diode laser

The authors have investigated the nonlinear transfer characteristics and temporal response of bistable three-section lasers within a broad wavelength interval (30 nm), when switched with picosecond optical pulses (20 ps) at a high repetition rate. The minimum input coupled switch-on energy was 0.7 fJ. The shortest switching time was 60 ps.<>     

基于对称型齿波导和纳米盘的类EIT和慢光效应

设计了一种新型的基于金属表面等离子体激元（SPPs）的亚波长金属-绝缘体-金属（MIM）型类电磁诱导透明（EIT）系统,该系统由一个直波导及其两边对称的齿形腔和纳米盘耦合而成。利用耦合模式理论对结构进行分析,并通过时域有限差分方法（FDTD）进行数值模拟。当齿形腔和纳米盘的共振频率相近,可以获得类EIT效应,改变齿形腔的长度和纳米盘的半径可以调节透明窗的位置。该装置可以用作高性能的类EIT滤波器,透过率高达77.5%,半高宽低至35.5 nm,群指数高达65,为高度集成光网络提供了一种新的方法,可应用于波长选择器、超快开关、光存储等设备。     

Optical switching between damped bistable soliton states usingperiodic amplifiers

The possibility of cyclic switching between bistable soliton states of the undamped generalized nonlinear Schrodinger equation (GNLSE) has been previously studied by the authors. It is shown that it is possible to maintain bistable solitary wave solutions of the GNLSE in the presence of damping by using localized periodic amplifiers and switch states from low to high and vice versa while maintaining stability. Provided that materials with the appropriate nonlinear mechanisms can be found or fabricated, this simulation points in the direction of two-state optical transmission systems that permit signal processing     

Effects induced by transit time on a coupled two-element opticalbistable device

The authors study the effects of finite transit time, i.e. delay, on dynamics in a coupled two-element optical bistable device. Finite transit time is considered because of signal propagation between the elements. It is shown that delay can be used as a measure of crosstalk between the coupled elements and that it increases the lethargy time. Thus, many interesting, transient phenomena take place both in hysteresis and pitchfork (symmetry-breaking) regimes. Symmetry-recovering crisis originating from the collision between the unstable periodic orbit and chaotic asymmetrical solution is predicated to occur for T≈τ (T: transit time, τ: response time of nonlinear medium). It is shown that symmetry-recovering crisis results in switching failure in set-reset (S-R) flip-flop operations with a pitchfork bifurcation structure