用时域有限差分法研究二维光子晶体传输特性

将时域有限差分方法用于光子晶体传输特性理论研究，分别计算了二维方型光子晶体TM模和TE模的透射率频率分布；根据光子晶体的标度不变性特征，在微波频段制作了光子晶体，并设计了实验装置；实验结果与计算结果一致表明：对于一定的入射方向，某些频率的光不能在光子晶体中传播。     

二维正方晶格光子晶体禁带特性

基于平面波展开法,以碳化硅构成二维正方晶格光子晶体,数值模拟了TE模、TM模二维光子晶体的禁带特性,结果表明,TE模更容易形成光子禁带。同时设计了以碳化硅构成二维正方晶格光子晶体波导,数值模拟了TE模、TM模波导的传输特性和禁带特性,结果表明,TE模构成的波导电磁波能够较好的传播,它们的光子禁带都没有出现。研究结论为光子晶体波导器件的开发提供参考。     

Experimental evidence of photonic crystal waveguides with wide bandwidth in two-dimensional Al_2O_3 rods array

A cross-shaped photonic crystal waveguide formed by a square lattice Al_2O_3 rods array is numerically and experimentally investigated. The band gap of the TE mode for the photonic crystals and transmission characteristics of waveguides are calculated by the plane wave expansion method and the finite element method.We perform the experiments in the microwave regime to validate the numerical results. The measured reflection and transmission characteristics of the photonic crystals show a large band gap between 8.62 and 11.554 GHz(relative bandwidth is 29.34%). The electromagnetic waves are transmitted stably in the waveguides, and the transmission characteristics maintain a high level in the band gap.     

用转移矩阵法数值研究二维正方介质柱光子晶体的传输特性

利用转移矩阵方法对二维正方介质柱光子晶体的传输特性进行了研究,数值计算研究了不同晶格、同一晶格柱体截面面积不同、放置方位角不同时光子晶体的传输特性。数值结果表明光子禁带的宽度与中心频率和晶格结构有很大关系,正方晶格更易形成平坦光子禁带,柱体截面面积大,则形成的禁带较宽,在其他因素相同的条件下柱体放置的方位角对光子禁带有重要影响。数值研究表明在正方介质柱下设计宽平坦光子禁带时,可以首先考虑正方晶格结构,其次设法使柱体截面尽量大一些,最后可通过柱体放置方位角来微调光子禁带的宽度与中心频率以达到设计要求。     

平均折射率为零的光子晶体中缺陷模频率特性的实验研究

利用传输线技术制备了左手材料,将左手材料与正常材料交替排列组合成平均折射率为零的一维光子晶体.该光子晶体在特定频段具有光子带隙,带隙不随晶格尺度和入射角的变化而改变.通过掺杂技术破坏光子晶体的周期性,可在禁带中引入缺陷模,这种结构的光子晶体可用于实现滤波器小型化和超强耦合.研究表明,通过调节缺陷的厚度可以控制缺陷模的频率,这为调节频率提供了一种方法.实验与仿真结果相符. 关键词： 左手材料 复合左右手传输线 光子晶体     

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。     

光子晶体的非严格周期性对其传输特性的影响

将时域有限差分法(FDTD)用于光子晶体传输特性研究。以二维方格子光子晶体TM模为研究对象。分别讨论了光子晶体制作过程中圆柱半径和品格常量误差对光子晶体传输特性和光子晶体器件性能的影响。研究表明。圆柱半径和品格常量的误差越大。光子晶体的带隙效果越差。在一定的误差范围里,光子晶体的传输特性能够被很好地保持;由于误差的存在,光子晶体点缺陷所形成的微腔的共振频率位置与理想情况发生了漂移;加工精度误差对光子晶体器件性能有较大影响。     

用传输矩阵法(TMM)研究二维光子晶体传输特性

将传输矩阵法(TMM)用于光子晶体传输特性的理论研究，采用Mur近似吸收边界和周期边界来截断计算区域，研究了以TM模正入射时，二维方格子光子晶体在完整周期结构下和有缺陷结构下的透过率谱；在微波波段制作了光子晶体模型，并设计了实验装置；实验与数值模拟计算取得了基本一致的结果。     

Anti-resonant reflecting photonic crystal waveguide (ARRPCW): modeling and design

In this paper, we apply an antiresonant reflecting layer concept in photonic crystal based waveguides. We have proposed a thin core ARRPCW with linear waveguide carved in it and hence calculated the transmission spectra for various length of waveguide and have shown that the longer waveguides in ARRPCW yields transmission with significantly high quality factor. Comparison of the transmission characteristics of normal conventional planar ARROW-B waveguides & ARRPCW has also been reported. The 2D FDTD numerical modeling reveals improved transmission for various lengths of planar ARROW and ARRPCW with low losses in long waveguides. Transmittance and quality factor are also calculated to confirm superior performance of the proposed design of ARROW based photonic crystal waveguide.     

Enlargement of complete two-dimensional band gap by using photonic crystal heterostructure

A two-dimensional photonic crystal heterostructure, which consists of two photonic crystals of a square lattice of circular columns with reverse dielectric configurations, is proposed. Photonic band gap properties are calculated using a plane-wave method and the transmission spectra are obtained. After optimization, the relative width of the complete band gap reached 13.8% based on the simple unit-cell shape and crystal lattice. The photonic crystal heterostructure opens up new ways of engineering photonic band gap materials and designing photonic crystal devices.     

Interference grating structures in photonic crystal circuits

Photonic Crystal Circuits have been widely investigated for various optoelectronics device applications. And the gratings in photonics devices are indispensable tool, which is very common for light manipulation. In this study, an interference grating structure formed by Gaussian beam interferences in photonic crystal waveguide such that having Kerr type nonlinearity is proposed and its transmission characteristics are investigated. Finite-Difference Time-Domain method is used to analyze the device characteristics. According to simulation results, the interference grating has shown special transmission characteristics that can bring tunability for photonic crystal devices. This can be an effective method for controlling optical signals in the photonic crystal for all optical switching/routing applications as a part of add/drop multiplexing.     

Transmission of light through a plane-parallel plate of a two-dimensional resonant photonic crystal

The transmission spectra of two-dimensional resonant photonic crystals of two types have been investigated. Crystals of one type consist of dielectric cylinders forming a square lattice filled by a resonant gas with mercury atoms, and crystals of the other type consist of cylindrical holes filled with a gas and forming a square lattice in a dielectric matrix. It has been established that characteristics of the spectrum of additional transmission arising in the band gap of the photonic crystal can be changed significantly by varying the gas pressure and the angle of incidence. It has been demonstrated that the calculated features in the transmission spectrum of the photonic crystal are stable with respect to a significant increase in the width of the atomic resonance.     

二维三角晶格光子晶体波导的出射光集束传播

为了解决光子晶体波导出射端光场控制, 同时解决二维三角晶格光子晶体波导出射光辐射困难的问题。利用二维三角晶格光子晶体设计了一种新型光子晶体波导出射口结构。在二维三角晶格光子晶体波导出射端引入两个微腔, 通过光波与微腔发生共振, 形成类似于三个点光源干涉的出射光, 同时进一步提出波导出射端喇叭口干涉出射光定向辐射的设计。通过这种微腔喇叭口设计, 利用时域有限差分法分析结果表明光波实现很好的定向辐射, 并且辐射距离显著提高。     

基于自准直效应的光子晶体异质结偏振分束器

基于光子晶体的自准直效应和禁带特性,提出了一种具有非正交异质结结构的光子晶体偏振分束器.无需引入缺陷或波导,可使光波在该结构中准直无发散地传输并实现分束功能,对制造工艺的要求大大降低.利用Rsoft软件,结合平面波展开法和二维时域有限差分法,对提出的偏振分束器进行了仿真研究.结果表明,该偏振分束器在一个较大的频率范围f=0.275—0.285(a/λ)内可实现横电(TE)和横磁(TM)模的大角度偏振分离,TE和TM模的透过率均在88%以上,偏振消光比分别大于26.57 dB和17.50 dB.该结构可应用到太赫兹波段的传输系统中,a=26μm,尺寸大小为572μm×546μm,在91—95μm波长范围内可实现TE和TM模的分离.利用该结构可设计用于光通信系统(n=3.48)的偏振分束器,a=426.25 nm,结构仅为9.38μm×8.95μm.本方案结构简单,易于集成,有望在集成光路的发展中发挥重要作用.     

光子晶体微环插分滤波器的理论分析与数值模拟

设计了基于二维正方晶格光子晶体微环的插分滤波器的基本结构,对其进行了时域耦合模理论分析,得到了输出端口的归一化透射率表达式。利用时域有限差分法对滤波器进行数值仿真,仿真结果与时域耦合模理论分析结果一致。结果显示,经过合理的参数调节,滤波器的传输效率可达到98％。这一分析方法同样可以适用于其他光子晶体结构。     

Band structure of photonic crystal fibers with silica rings in triangular lattice

The characteristics of the cladding band structure of air-core photonic crystal fibers with silica rings in triangular lattice are investigated by using a standard plane wave method. The numerical results show that light can be localized in the air core by the photonic band gaps of the fiber. By increasing the air-filling fraction, the band gap edges of the low frequency photonic band gaps shift to shorter wavelength, whereas the band gap width decreases linearly. In order to make a specified light fall in the low frequency band gaps of the fiber, the interplay of the silica ring spacing and the air-filling fraction is also analyzed. It shows that the silica ring spacing increases monotonously when the air-filling fraction is increased, and the spacing range increases exponentially. This type fiber might have potential in infrared light transmission.     

光子晶体缺陷结构的特性

基于平面波展开法,设计了二维正方晶格和三角晶格光子晶体缺陷结构,数值模拟了TE模、TM模式的光子晶体禁带特性,计算了二维三角晶格光子晶体缺陷结构的模式分布。结果表明,光子晶体缺陷结构能够形成很好的禁带特性和模式结构,研究结论为光子晶体波导器件的开发提供参考。     

不同结构光子晶体的带隙特性

基于平面波展开法研究光子晶体的带隙特性,数值模拟了横磁波和横电波在三角晶格和正方晶格构成的二维光子晶体中的带隙特性,得到了三角晶格较正方晶格更容易出现带隙,且三角晶格的横电波光子带隙较大.实验结果为光子晶体器件的设计提供理论依据.     

A novel architecture of ultracompact pulse position modulator in photonic crystals

We propose and analyze a novel photonic crystal pulse position modulator utilizing a coupled cavity waveguide delay line. Also, a nonlinear photonic crystal directional coupler is used as an all-optical switch in the proposed structure. The input data acts as the control signal of the switch and activates the switching operation. We show that the device size can be reduced significantly by designing the delay line to achieve a reduced group velocity and a quasi-flat impurity band. The size of the designed modulator is 32a × 16a, where a represents the lattice constant of the photonic crystal. The characteristics of the device are investigated by finite-difference time-domain (FDTD) and plane wave expansion (PWE) methods.     

光子晶体光纤的正交函数模型

提出了一种用于分析光子晶体光纤的正交函数模型。采用一种新型超格子的构造方法,将光子晶体光纤的横向介电常量表示为两种周期性结构叠加。将横向电场以厄密一高斯函数展开,利用正交函数的性质,将全矢量波动方程转化为矩阵本征值问题,求解本征值问题可得到模式的传输常量及模场分布。利用此模型举例讨论了椭圆孔三角格子光子晶体光纤的模场分布和偏振特性以及三角格子光子晶体光纤的色散特性和有效面积等传输特性。作为一种普适的模型,此方法还可适用于四方结构、蜂窝结构及椭圆孔等多种结构光子晶体光纤。