Slotted Photonic Crystal Microring Resonators

We propose using a slotted photonic crystal nanobeam to construct a microring resonator. The transmission characteristics of the slotted photonic crystal nanobeam and the microring resonator are demonstrated by two-dimensional finite-difference time-domain simulation, and the mechanism of these characteristics is analyzed considering the introduction of the slot. The refractive index sensitivity of the slotted photonic crystal microring resonator is evaluated to be larger than those of a slot waveguide microring resonator and a nonslotted photonic crystal microring resonator.     

Polarization beam splitters based on a two-dimensional photonic crystal of negative refraction

A two-dimensional metallo-dielectric photonic crystal of negative refraction was designed for the application of polarization beam splitters. To match the refractive index of air, the effective refractive index of the designed photonic crystal is -1 for TE polarization and +1 for TM polarization. Two types of polarization beam splitter are presented.     

Photonic Crystal Polarizing and Non-Polarizing Beam Splitters

A polarizing beam splitter （PBS） and a non-polarizing beam splitter （NPBS） based on a photonic crystal （PC） directional coupler are demonstrated. The photonic crystal directional coupler consists of a hexagonal lattice of dielectric pillars in air and has a complete photonic band gap. The photonic band structure and the band gap map are calculated using the plane wave expansion （PWE） method. The splitting properties of the splitter are investigated numerically using the finite difference time domain （FDTD） method.     

光子晶体环形谐振腔异质结构超微多路光分束器

基于直波导和环形谐振腔的耦合特性,设计了一种新型、高效的二维光子晶体异质结构光分束器.时域有限差分法模拟表明,该设计仅仅通过改变介质柱的折射率,使光场发生重新分布,便可实现输出能量的均分或自由分配.在通信波长范围,该设计结构尺寸小、分束角度大、分束率高,这些特性使其在光通信领域具有重要的应用前景.     

A tunable power splitter based on modes coupling and self-collimation effect in two-dimensional photonic crystals

A tunable power splitter is proposed in a two-dimensional photonic crystal with a line defect composed of two rows rods, whose refractive index can be controlled artificially. This device is working at a self-collimation frequency. The finite difference time domain (FDTD) simulations show that the beam splitting ratio is a function of the refractive index of line defect. If the index varies from 3.0 to 3.5, the beam intensity of one output port decreases from 87.2% (normalized by the input beam) to 0 while the intensity of the other output port increases from 8.98% to 100% monotonically. The coupling between the self-collimation mode and the defect mode is used to explain the working mechanism.     

基于各向异性介质的偏振分束器

利用各向异性介质与各向同性介质构造了一维光子晶体,利用传输矩阵方法分析了它的能带结构,指出利用各向异性介质可以构造高消光比,全角度的偏振分束器件,并分析了它的理论基础.对影响偏振分束带宽的因素进行了分析.为进一步改进设计提出了方向.     

光子晶体中基于有效折射率接近零的光束准直出射

利用平面波展开法(PWM)和时域有限差分法(FDTD)研究了二维正方格子光子晶体靠近禁带边沿附近频率光波的传输特性.研究发现,若有效折射率接近于零,可出现光束从晶体表面准直出射的现象,且光束的出射方向只与晶体表面的取向有关,而与晶格取向无关.这种现象与自准直现象有很大不同.     

Integrated photonic glucose biosensor using a vertically coupled microring resonator in polymers

A photonic glucose biosensor incorporating a vertically coupled polymeric microring resonator was proposed and accomplished. The concentration of a glucose solution was estimated by observing the shift in the resonant wavelength of the resonator. For achieving higher sensitivity the contrast between the effective refractive index of the polymeric waveguide and that of the analyte was minimized. Actually, the effective refractive index of the polymeric waveguide (n = ∼1.390) was substantially close to that (n = ∼1.333) of the fresh solution with no glucose. The fabricated resonator sensor with the free spectral range of 0.66 nm yielded a sensitivity of ∼280 pm/(g/dL), which corresponds to ∼200 nm/RIU (refractive index units) as a refractometric sensor, and provided a detection limit of refractive index change on the order of 10⁻⁵ RIU.     

光子晶体自准直光束偏振分束器

结合能带图和等频图分析,基于光子晶体自准直效应和光子带隙,设计了一种紧凑、高效的偏振分束器.时域有限差分法(FDTD)模拟表明,该设计可以在一个较大的频率范围f=0.268—0.278(c/a) 内实现TE模和TM模的高效(85%)、大角度(90°)分离.在光通讯波长λ=1.55 μm,该设计尺寸仅为9 μm×9 μm.这些特性使其在光通讯领域中具有重要的应用前景. 关键词： 光子晶体 偏振分束器 自准直     

The beam splitting in the photonic crystal at a degenerate state

In this paper, using the plane-wave expansion and finite difference time-domain methods, the photons behavior in the photonic crystal is investigated. Theoretically, when a polarized wave is incident from the background medium to the photonic crystal, the beam propagation directions in the photonic crystal determined by two methods are approximately same. But in this paper, the results exhibit that there is an additional direction obtained by the finite difference time-domain method compared with the plane-wave expansion. Considering basic physical mechanism of the photon behavior, the present work circumvents the electromagnetic field distribution in the photonic crystal at a degenerate state, which can reasonably explain the phenomenon. Finally, it shows that a photonic crystal can be properly designed to achieve double refraction simultaneously at one frequency, which can also offer new thoughts and foundation for the novel beam splitter that applied to many optical systems.     

基于光子晶体自准直环形谐振腔的全光均分束器

通过等频图分析并结合时域有限差分法模拟,在一个与偏振态无关的自准直光子晶体环形谐振腔中,研究发现当环形谐振腔内的光传输距离改变时,横电波(TE)和横磁波(TM)两种偏振态的光在通过环形谐振腔之后的输出将会随之变化并呈现出不同的周期性.通过选择适合的传输距离,实现了TE,TM自准直的情况下同时分束50%的结果,构成了一种基于光子晶体自准直环形谐振腔的全光均分束器.全光均分束器扩大了分束器的运用范围,也会在高密度集成光路中发挥重要的作用. 关键词： 光子晶体 环形谐振腔 自准直 分束器     

新型超宽带双芯光子晶体光纤偏振分束器的研究

提出了一种新型超宽带双芯光子晶体光纤偏振分束器. 应用全矢量有限元法,系统地研究了光纤结构参数对偏振分束器带宽和偏振分束器长度的影响. 分析结果表明：增加掺氟区折射率,既能提高分束器带宽,也能减少分束器长度;增大光纤中空气孔的孔距及孔径与孔距比,可以增加分束器的带宽,但同时也会导致分束器的长度增大,使得器件尺寸增大. 因此,在设计中需兼顾分束器的带宽和长度来选取光纤的结构参数. 通过结构参数的优化,设计出一种短长度、高消光比和超宽带的偏振分束器,其长度为7.362 mm,消光比高于20 dB的带宽为600 nm. 关键词： 光子晶体光纤 偏振分束器 超宽带 全矢量有限元法     

Highly collimated emission from a left-handed photonic crystal with a quasi-cavity

We study the collimated emission characteristics from a dipole source inside a negative-effective-refractive-index photonic crystal with a quasi-cavity constructed by a concave photonic crystal reflector. The emissions along the ±X and −Y directions are forbidden by the quasi-cavity, so that most emissions propagate along the +Y direction. Simulation results show that a narrow collimated beam is achieved due to the near-zero negative effective refractive index. Moreover, the half-power beam width of such a collimated beam can be reduced to 3.48° by optimizing the size of the source area. Such a compact structure would have potential applications in micro-optical devices.     

一种新型的光子晶体偏振光分束器的设计

基于光波在直波导和复合结构光子晶体中的传播特性,结合平面波展开法和时域有限差分法,提出并讨论了一种新型的超紧凑的光子晶体偏振光分束器. 它是由输入波导,分束结构和输出波导三部分组成. 对这种结构的三角晶格光子晶体光分束器的数值计算与模拟结果表明,该结构可以实现TE模和TM模的高效大角度分离,并且在通信波段设计尺寸小,这些特性使其在未来的集成光回路中有着重要的应用前景. 关键词： 偏振光分束器 能带结构 平面波展开法 时域有限差分法     

Design and simulation of a switch based on nonlinear directional coupler

In this paper, we have analyzed a nonlinear photonic crystal directional coupler by the finite difference time domain method. We have tried to increase the coupling efficiency and also reduce the coupling length in linear and nonlinear states in this device. In this coupler, refractive index of the rods of the central row is tuned by input signal power due to nonlinear Kerr effect; therefore, input signal beam can be controlled so as to be exchanged between two output ports. Physical length is chosen to be 24a so as to have the highest output power ratio and also the smallest amount of power required for nonlinear performance.     

Dispersion-based beam splitter in photonic crystals

A novel implementation of a dispersion-based beam splitter in a photonic crystal (PhC) is proposed. The beam splitter consists of two periodic structures: a nonchannel dispersion-guiding region and a splitting structure operating inside the photonic bandgap. The dispersion-guiding PhC structure is used to route the optical wave by exploiting the dispersion properties of the lattice. An arbitrary power ratio between the output beams can be achieved by varying the parameters of the splitting structure. Within the studied range of splitting structures, high output power was observed and verified experimentally.     

二维光子晶体T型波导分支器数值模拟研究

采用平面波展开法和时域有限差分法,对GaAs二维正方晶格光子晶体的色散特性和带隙结构进行了数值模拟研究,并对GaAs二维光子晶体线缺陷构成的T型波导分支器的微波传输特性进行了模拟和优化。数值模拟结果表明,光子晶体填充比对带隙结构有显著地影响。通过在拐角处插入额外的电介质棒对GaAs二维正方光子晶体T型波导分支器进行优化,数值模拟的结果表明,优化的GaAs二维正方光子晶体T型波导分支器在一阶带隙范围内透射系数将提高到0.96以上。     

基于1×4光子晶体波导分束器的特性研究

光子晶体波导分束器是集成光学电路的重要组成元件。设计一种线缺陷1×4光子晶体分束器,用时域有限差分法研究其特性。实验结果表明:输出端的透射传输特性随入射光的波长和分支的几何形状有关,并且入射波分别相等地流入4个输出端口。为了减少1×4分束器在3个Y型分支区的反射,通过调节分支区的可调介质柱的半径R,可使每个输出端口输出较高的透射率。     

红外区二维光子晶体偏振分光镜透射谱分析

采用时域有限差分（Finite-Difference Time-Domain,FDTD）法模拟了垂直入射红外波段二维光子晶体偏振分光镜的透射谱,从而验证了用平面波展开方法计算的二维光子晶体能带结构.用电子束蒸发方法在光栅基板上制备了Ge/BaF2多层膜,实现了二维光子晶体偏振分光镜.实验初步证明了这种光子晶体在垂直入射时具有偏振特性,分析了实验结果与理论计算之间偏差的产生原因.     

GaN基蓝光LED中光子晶体对提取效率及发光偏振态的影响

为了提高氮化镓基蓝光发光二极管的发光提取效率,在其电流扩展层上生长光子晶体.讨论了光子晶体结构周期、刻蚀深度和占空比参数与提取效率的关系,并采用时域有限差分法进行模拟计算.结果表明在晶格周期为300nm、占空比为60%和刻蚀深度为200nm的条件下,生长光子晶体结构后,氮化镓基蓝光发光二极管的提取效率提升了27.93%.研究了激励源在光子晶体晶格周期内位置变化对提取效率的影响,拟合得到更符合实际物理意义的氮化镓基蓝光发光二极管发光提取效率函数.利用等效折射率理论和法布里-珀罗薄膜干涉模型解释了氮化镓基蓝光发光二极管中TE模和TM模偏振之间提取效率的差异,数值仿真得到最大差异值为1.442倍,从而获得高偏振对比度光源.用该结构参数制备的发光二极管器件应用于液晶显示背光源,可提高液晶显示的能耗效率.