压缩型双缺陷椭圆孔光子晶体光纤

提出了一种通过横向压缩普通圆孔光子晶体光纤,得到双缺陷椭圆孔光子晶体光纤的方法.所提出的双缺陷光子晶体光纤具有高双折射率,采用全矢量有限元方法和各向异性介质完美匹配层方法对该光子晶体光纤的双折射特性和约束损耗特性进行了研究.理论模拟结果表明所提出的光子晶体光纤的双折射率可以达到10－2量级.     

基于椭圆孔包层和微型双孔纤芯的新型高双折射光子晶体光纤

设计了一种新型高双折射光子晶体光纤,即其包层引入椭圆形空气孔,且以三角晶格方式周期排列,纤芯引入亚波长尺寸(~0.16 μm)的微型双孔结构阵列.采用全矢量有限元法和各向异性完美匹配层边界条件分析了该型光子晶体光纤的双折射特性和色散特性,详细介绍了该光子晶体光纤在不同的椭圆率、椭圆归一化面积、微型双孔孔径、两小孔之间间距的情况下双折射和限制损耗随波长的变化曲线.模拟结果表明,通过同时在包层和纤芯引入非对称性,获得了较高的双折射(~10^-3量级)和极低(~10^-4 dB/km)的限制损耗.提供了一种新的光子晶体光纤设计方法,即通过同时在包层和纤芯引入新结构来同时获得高双折射和低损耗.     

基于椭圆孔微结构纤芯的高双折射光子晶体光纤

提出了一种在纤芯引入微小椭圆孔实现高双折射光子晶体光纤的方法.采用全矢量有限元方法和完美匹配层条件,依次研究了光子晶体光纤在纤芯中引入单个、双个、三个微小椭圆孔情况下的双折射特性.模拟结果表明,纤芯微小椭圆孔主导了光子晶体光纤的双折射特性,其参量及个数对双折射有着重要的影响,增大椭圆面积、椭圆率可以进一步提高光子晶体光纤的双折射.最后设计和研究了一种采用三环阵列椭圆孔微结构纤芯的光子晶体光纤,其双折射可以达到2.7×10－3.     

新型矩形点阵光子晶体光纤的高双折射负色散效应

设计了一种新型矩形点阵光子晶体光纤,该光纤纤芯缺失一根空气柱,包层沿光纤长度方向在普通矩形点阵光子晶体光纤中每两列之间隔一行插入一列空气孔而形成正方形网孔结构.采用全矢量有限元法并结合各向异性完美匹配边界条件,对该光纤的色散、双折射和约束损耗进行了数值模拟.结果发现,该光纤具有高双折射负色散效应和较强的模约束能力,约束损耗小于10-2dB·m-1,通过改变光纤结构参数(即空气孔间隔Λ和相对孔间隔d/Λ),可以调节该光纤高双折射负色散工作波长.若调整光纤结构参数Λ=2.0μm,d/Λ=0.4,该光纤在C波段(1.53—1.565μm)呈现负色散并具有负色散斜率,双折射高达10-2,非线性系数接近55km-1W-1.该光纤将在保偏光通信、色散补偿以及基于四波混频的波长转换器设计等方面具有重要的应用.     

空气孔正方形排列的低损耗高双折射光子晶体光纤的数值模拟

提出了一种正方形排列渐增空气孔高双折射光子晶体光纤，并利用多极方法对光纤基模的模场分布、色散、双折射以及损耗特性进行了数值模拟.模拟结果表明利用这种结构可以在包层空气孔层数较少的情况下实现极低的限制损耗，通过调节内层空气孔的分布可以有效地控制光纤的双折射和色散特性.本结果对高双折射光子晶体光纤的制备具有一定的指导意义. 关键词： 光子晶体光纤 双折射 限制损耗 多极方法     

Photonic crystal fiber with high birefringence and low confinement loss

In this paper, a highly birefringent index-guiding photonic crystal fiber with low confinement loss is proposed by enlarging the central row of air holes in the structure. By employing the multipole method, properties of this structure, including the effective index, birefringence and confinement loss, are investigated. Simulation results indicate that high birefringence of 1.65 × 10⁻³ can be reached at the wavelength of 1.55 μm, and a low confinement loss on the order of 10⁻⁶ dB/km can be achieved at the same wavelength. Moreover, the impacts of air hole sizes on birefringence and confinement loss are also analyzed in detail.     

Bending insensitive large mode area photonic crystal fiber

A novel kind of large mode area photonic crystal fibers (PCFs) are proposed in this paper. In order to achieve large effective mode area, a novel technique is applied to seven missing air hole PCF structures. The modal characteristics of PCF structures such as effective mode area, confinement loss, chromatic dispersion properties with doped cores, are investigated by employing the full vectorial finite element method (FEM). Simulation results demonstrate that effective mode area and confinement losses of fundamental mode simultaneously improved by applying our novel technique to proposed structures. The effects of bending on confinement losses of the proposed PCFs have been thoroughly investigated. Additionally, confinement losses of first higher order modes are presented and the possibility of stripping them in a simple way is discussed.     

Analysis of nonlinear PCF for birefringence application using FDTD method

The effect of ellipticity on birefringence in a hexagonal photonic crystal fiber having elliptical air holes with Kerr nonlinearity is investigated, with and without defect using finite difference time domain (FDTD) simulations. It is found that the birefringence increases with the increase of ellipticity. Further this analysis is extended to a double defect structure, where two adjacent air holes are omitted horizontally from the hexagonal structure. This double defect structure is found to have more birefringence than the structure without defect. It is raveled that birefringence due to no defect is more for lower value of ellipticity; however at higher value of ellipticity, birefringence due to double defect is more than the one that could be due to no defect.     

Research on terahertz photonic crystal fiber characteristics with high birefringence

A new high birefringence photonic crystal fiber is proposed within the terahertz frequency region. It has two types of claddings, the inner is composed of six ellipse air holes arranged in a honeycomb array and the outer surrounded by circle holes. By using the full vector finite element method with anisotropic perfectly matched layers absorption boundary condition, the birefringence, chromatic dispersion and confinement loss of the fundamental mode are evaluated. The results show that the birefringence can achieve 10⁻³ when the wavelength increases from 600 μm to 900 μm. This structure will provide some reference value for the designing of high birefringence terahertz photonic crystal fiber.     

Dispersion properties,birefringence and confinement loss of rotational elliptic air-hole photonic crystal fiber

Dispersion properties, birefringence and confinement loss between the circular air-hole photonic crystal fiber (CAHPCF) and rotational elliptical air-hole photonic crystal fiber (REAHPCF) are investigated numerically by means of a plane-wave expansion method and a finite element method. Results show that the performances of REAHPCF on flatter dispersion curve, single mode, high birefringence and low confinement loss is better than that of CAHPCF.     

八边形结构的双折射光子晶体光纤

提出一种新型的双折射光子晶体光纤,在正八边形的基础上改变纤芯附近的几个空气孔的直径产生双折射.利用多极法对该光纤基模的模场分布、色散、限制损耗及双折射特性进行数值分析,并且分析了一些参数对双折射的影响.计算了具有相同参数的六边形结构光子晶体光纤的色散系数、限制损耗及双折射率.研究表明,具有相同参数的八边形结构光子晶体光纤比六边形结构光子晶体光纤的双折射率明显提高,限制损耗大幅度减小,零色散波长也向短波方向移动. 关键词： 光子晶体光纤 双折射 色散 限制损耗     

矩形孔光子晶体光纤

采用全矢量有限元方法和完美匹配层条件,研究了一种在光纤包层中引入矩形孔的光子晶体光纤,提出一种实现高双折射光子晶体光纤的方法.模拟结果表明矩形孔光子晶体光纤具有椭圆孔光子晶体光纤类似的高双折射特性,其双折射高达0.01的量级,两种光子晶体光纤的模场、双折射、约束损耗等特性基本类似.     

Multiple defect-core hexagonal photonic crystal fiber with flattened dispersion and polarization maintaining properties

In this paper, we present a dispersion controlling technique with a multiple defect-core hexagonal photonic crystal fiber (MD-HPCF). By omitting air holes in the core region of the conventional HPCF and adjusting the size of air holes around the newly formed core, we can successfully design low flattened dispersion PCF with low confinement loss, as well as high birefringence. The low flattened dispersion feature, as well as the low confinement losses and high birefringence are the main advantages of the proposed PCF structure, making it suitable as chromatic dispersion controller, dispersion compensator, and/or polarization maintaining fiber.     

Improved high birefringence photonic crystal fibres with dispersion flattened and single mode operation

A kind of improved high birefringence photonic crystal fibre (PCF) is proposed in this paper. The characteristics of birefringence, dispersion and leakage loss are studied by the multipole method. Numerical results show that the improved PCF possesses the properties of a flat dispersion and single mode operation. Moreover, with the operating wavelength λ = 1.55μm, the modal birefringence increases greatly in comparison with that of the original PCF, and the leakage loss is about 10⁴ times smaller than that of the original PCF because the modification gives rise to the strong confinement of guided modes. It is expected that the improved PCF can be used as high birefringence and dispersion flattened fibres.     

高双折射的混合格子太赫兹光子晶体光纤的设计与研究

提出了一种新型高双折射的混合格子太赫兹光子晶体光纤,通过对芯区亚波长尺寸的空气孔进行多种格子组合排列,增加结构的非对称性实现高的模式双折射. 全文仿真建模采用专业的有限元计算软件COMSOL Multiphysics 4.0,结果表明:混合格子太赫兹光子晶体光纤在很宽的频率范围内都具有较高的双折射(达到10^-2)和低的限制损耗,且通过改变光纤的某些参数可以灵活地控制其双折射或限制损耗特性. 相比于同类光通信波段光纤,由于太赫兹波波长较大,能够降低芯区微结构加工的难度,具有可行性. 关键词： 双折射 混合格子 太赫兹光子晶体光纤 限制损耗     

Design of defect-core in highly birefringent photonic crystal fibers with anisotropic claddings

The influence of defect-core on the birefringence and confinement losses of rectangular-lattice photonic crystal fibers are investigated numerically by applying the multipole method. Numerical results illustrate that the birefringence in such fibers is determined not only by the arrangement of air holes in the cladding but also the shape of the core. It is found that asymmetry of the core represented by its rectangular shape implies a higher effective index of the mode that is parallel with the longer side of the rectangle, whereas the anisotropic rectangular-lattice cladding gives rise to just the opposite effect and thus the resulting birefringence can be controlled by a proper combinations of both mechanisms. In particular, effect of the asymmetry of the core on the birefringence is dominant for shorter wavelength. Increased birefringence and reduced confinement loss can be achieved, if we form the core by the omission of several air holes in a row to reduce its negative effect on the birefringence. On the other hand, when asymmetry is increased in the other direction, a negative birefringence at shorter wavelength can be achieved. This occurs due to the fact that asymmetry of the core at higher frequencies overcomes the effect of the asymmetric cladding. As a result, its possible to achieve zero birefringence in anisotropic cladding photonic crystal fiber with an asymmetric core.     

一种新型的基于四孔单元光子晶体光纤的设计与分析

设计了一种基于四孔单元的光子晶体光纤,它可以满足光通信系统中高双折射率、负色散和低限制损耗的要求,比起通常的三角结构光纤有着更高的双折射率,并且结构制作也较简单。采用全矢量有限元法和各项异性完美匹配层法对所设计的光纤进行了仿真研究。仿真结果表明:该光纤在1.55μm波长处可获得10~(-2)数量级的双折射率,在较宽广的波段范围具有大的负色散,限制损耗低于10~(-9)dB/m;该光纤在保偏光纤、单极化单模光纤、色散补偿光纤等方面具有重要的应用。     

微结构纤芯对光子晶体光纤基本特性的影响

本文设计了两种具有微结构纤芯的光子晶体光纤（PCFs）——矩形芯和椭圆芯PCFs,利用电磁场散射的多极理论研究了这两种光纤的基本特性.发现在光纤包层气孔不变的情况下,仅通过调节纤芯气孔的大小就可以灵活地调节光纤的双折射、色散和非线性特性.随着纤芯气孔半径r₁的增大,两种纤芯结构的PCFs表现出如下特点：双折射度增大且最大双折射度对应的波长发生红移,零色散波长由一个增加到三个,短波段非线性系数增大而长波段非线性系数减小.r₁=0.4 μm的椭圆芯PCFs的三个零色 关键词： 微结构纤芯光子晶体光纤 双折射 色散 非线性     

Polarization-maintaining photonic crystal fibers with near-zero flattened dispersion in 1.06 μm waveband for medical applications

In this paper we present the design of a modified hexagonal photonic crystal fiber (PCF) having high birefringence and a near-zero flattened dispersion. Using the finite-difference method (FDM), it is shown that the proposed multiple Gedoped core hexagonal PCF exhibits a high birefringence of order 10⁻³ and a nearly zero flattened dispersion in the optical coherence tomography (OCT) waveband. In addition, the proposed PCF has a confinement loss of less than 10⁻⁸ dB/m at 1.06 μm. PCFs with such properties are considered suitable for both endoscopic OCT and other experimental setups employing 1.06 μm lasers.     

全矢量有限元模型及其在光波导中的应用

为了研究光波导和光子晶体光纤的模式特性和传输特性,从矢量波动方程出发,推导出了各向异性介质中场微分方程复数泛函表达式,利用棱边/节点混合元离散了该泛函,加入了各向异性介质匹配层边界条件,得到关于传播常量的广义特征值方程.以矩形波导为例,对各向异性介质匹配层边界条件的吸收特性进行了研究,得到了基模以及几个高阶模的场分布、色散曲线和损耗曲线.结果表明该方法可靠有效.对正六边形晶格光子晶体光纤进行了分析.数据表明：光纤有效折射率随空气孔直径或波长的增大而减小,但与空气孔圈数无关;光纤限制损耗(confinement loss)随波长增大近似成指数增大,而增加空气孔直径或者空气孔圈数则可使之显著降低.