一种新型的多包层光子晶体光纤的分析方法

传统有效折射率方法只能模拟具有相同空气孔大小的单包层光子晶体光纤.针对这一问题,提出了一种改进的有效折射率法,能够计算具有不同孔径的多包层光子晶体光纤的传输特性.并用此方法对三包层光子晶体光纤的基模有效折射率和色散等特性进行了数值模拟,结果与多极法模拟出的结果符合得很好.这种改进的有效折射率法拓展了传统有效折射率法的适用范围,对快速准确地分析和设计具有不同传输特性的多包层光子晶体光纤提供了理论依据. 关键词： 光子晶体光纤 多包层 有效折射率方法 色散     

Kagome结构空芯光子晶体光纤纤芯参数对传输特性的影响

应用全矢量有限元方法,研究大间距Kagome结构空芯光子晶体光纤中纤芯的大小、形状与壁厚对光纤传输损耗谱的影响。结果表明,某些纤芯尺寸会造成包层中的结构缺陷,易使纤芯基模、表面模及包层模之间发生能量耦合,产生较大损耗。而纤芯形状与壁厚的改变会引起表面模式的变化,从而影响发生在基模与表面模之间反向耦合的位置和强度,使光纤传输频带变窄和损耗变大。据此,提出Kagome结构光纤的纤芯设计思路,即纤芯的大小应使包层保持完整的微结构,纤芯形状应与包层中的单元微结构相楔合,纤芯壁厚应与包层中玻璃支柱的宽度相同。     

Dispersion characteristics of hollow-core photonic crystal fibers

This work is devoted to the study of hollow-core photonic crystal fibers (HCPCF) dispersion properties. An effective scheme of HCPCF eigenmodes analysis, lying in separate dispersion diagrams calculation for the cladding and for the HCPCF itself, was proposed. General recommendations concerning selection of proper fiber parameters were given. The text was submitted by the authors in English.     

改进的全矢量有效折射率方法分析光子晶体光纤的色散特性

得到了全矢量有效折射率方法中归一化等效纤芯半径(p/Λ)随归一化空气孔直径(d/Λ)和归一化频率(Λ/λ)的变化关系，修正了p/Λ为固定值的不合理取法，得到了改进的全矢量有效折射率方法(IFVEIM).用IFVEIM计算的基模有效折射率和总色散等模式特性与多极法的结果和试验值相比较都具有很好的一致性，将基模有效折射率的误差减小了2—3个数量级.用IFVEIM详细地分析了光子晶体光纤的色散特性，得到了色散值、波长、孔间距、d/Λ之间的相互变化关系. 关键词： 光子晶体光纤 有效折射率方法 等效纤芯半径 色散     

Light propagation in highly birefringent photonic liquid crystal fibers

Photonic liquid crystal fibers have already been demonstrated as a promising perspective for creation of new classes of dynamically tunable optical fiber devices. By combining different geometries of photonic crystal fibers with a variety of different liquid crystals it is possible to obtain a new generation of fibers with dynamically tunable properties, e.g., transmission spectra, attenuation or dispersion. In this paper, tunable birefringence in a commercially available highly birefringent Blazephotonics PM-1550-01 photonic crystal fiber selectively filled with a low birefringence liquid crystal has been experimentally demonstrated. Theses experimental results have been compared with simulations based on the multipole method.     

Experimental verification of improved effective index method for endlessly single mode photonic crystal fiber

We report the experimental verification of Improved Effective Index Method (IEIM) for Endlessly Single Mode Photonic Crystal Fibers (ESM PCFs) from far field intensity measurements. In this paper all the key parameters i.e. V-Number, effective refractive index of the cladding, radius of the core and numerical aperture have been obtained from the experimentally measured far-field intensity pattern of ESM-PCFs. It is shown that the transmission characteristics of ESM-PCFs match with the simulation result obtained using IEIM and also with the core diameter of PCF obtained from scanning electron microscope (SEM) within the experimental limit.     

Improved effective-index method for analysis of photonic crystal fibers

We propose, for the first time to our knowledge, an improved effective-index method (IEIM) that has the advantage of high speed and much better accuracy than the conventional effective-index method. The modal properties computed with the IEIM, such as effective index and dispersion, are closely matched to those of the multipole method as well as to experimental values.     

Tunable properties of light propagation in photonic liquid crystal fibers

Tunable properties of light propagation in photonic crystal fibers filled with liquid crystals, called photonic liquid crystal fibers (PLCFs) are presented. The propagation properties of PLCFs strongly depend on contrast between refractive indices of the solid core (pure silica glass) and liquid crystals (LCs) filing the holes of the fiber. Due to relatively strong thermo-optical effect, we can change the refractive index of the LC by changing its temperature. Numerical analysis of light propagation in PLCF, based on two simulation methods, such as finite difference (FD) and multipole method (MM) is presented. The numerical results obtained are in good agreement with our earlier experimental results presented elsewhere [1].     

Cavity-mode calculation of L3 photonic crystal slab using the effective index perturbation method

This paper mainly describes that the effective index perturbation (EIP) technique in combination with two-dimensional (2D)/three-dimensional (3D) PWE methods predicts resonant mode frequencies and mode patterns for the L3 photonic crystal slab cavity, which substantially reduces the computation time and computer memory without losing accuracy. The simulation results show that when the perturbed effective index by matching dielectric band edge is used, the fundamental resonant mode has small calculation frequency error; however, when the effective index obtained by the standard effective index method (EIM) is used, it is appropriate for predicting higher-order resonant modes, and the micro-photoluminescence experiments verify the predictions of the theoretical model. In addition, mode profiles of the L3 cavity with both the displacement of the end-holes and the base cavity structure can also be accurately predicted.     

Nonlinear propagation effects in antiresonant high-index inclusion photonic crystal fibers

We experimentally and numerically investigate femtosecond-pulse propagation in a microstructured optical fiber consisting of a silica core surrounded by airholes that are filled with a high-index fluid. This fiber combines the resonant properties of hollow-core bandgap fibers and the high nonlinearity of index-guiding waveguides. A range of nonlinear optical effects can be observed, including soliton propagation, dispersive wave generation, and a Raman self-frequency shift. Tuning the center wavelength of the laser and varying the refractive index of the fluid lead to different propagation effects, mediated by the strongly wavelength-dependent group-velocity dispersion in these photonic bandgap confining structures.     

Lateral stress-induced propagation characteristics in photonic crystal fibres

Using the finite element method, this paper investigates lateral stress-induced propagation characteristics in a photonic crystal fibre of hexagonal symmetry. The results of simulation show the strong stress dependence of effective index of the fundamental guided mode, phase modal birefringence and confinement loss. It also finds that the contribution of the geometrical effect that is related only to deformation of the photonic crystal fibre and the stress-related contribution to phase modal birefringence and confinement loss are entirely different. Furthermore, polarization-dependent stress sensitivity of confinement loss is proposed in this paper.     

Parameter analysis of a photonic crystal fiber with raised-core index profile based on effective index method

Photonic crystal fibers (PCFs) with a stepped raised-core profile and one layer equally spaced holes in the cladding are analyzed. Using effective index method and considering a raised step refractive index difference between the index of the core and the effective index of the cladding, we improve the characteristic parameters such as numerical aperture and V-parameter, and reduce its bending loss to about one tenth of a conventional PCF. Implementing such a structure in PCFs may be one step forward to achieve low loss PCFs for communication applications.     

双芯高双折射光子晶体光纤耦合特性研究

设计了一种双芯高双折射光子晶体光纤,采用多极法（multipole method）和光纤的模式耦合理论研究了光纤的双折射、耦合长度以及色散特性.数值研究发现,对于空气孔节距 Λ=1.2　μm,空气孔直径d=1.0　μm的光纤,在1.55　μm处双折射度为1.24×10^-2;对应x偏振模的耦合长度为21.6　μm,对应y偏振模的耦合长度为24.3　μm. 这种具有高保偏度和极短耦合长度的双芯光子晶体光纤对于微型光子器件的研制具有重 关键词： 光子晶体光纤 双芯 双折射 耦合长度     

Elliptical-hole photonic crystal fibers

We study the dispersive properties of photonic crystal fibers (PCF's) with elliptical air holes. The unusual guidance of PCF leads to novel behavior of the birefringence, group-velocity walk-off, and dispersion parameters, including the possibility of zero walk-off with high birefringence in the single-mode regime. A number of these effects are closely tied to the underlying radiation states of the air-hole lattice.     

胶体晶体微结构光纤传输特性研究

介绍了胶体晶体微结构光纤的结构, 采用时域有限差分法研究了微结构胶体晶体光纤的传输特性. 建立了该结构的FDTD模型, 计算了其透射谱和不同波长的传输场分布. 搭建了光学系统, 测量了实验制备的胶体晶体微结构光纤的透射谱, 并将其与模拟所得透射谱进行比较, 具有良好的一致性. 胶体晶体微结构光纤的传输场分布结果表明, 胶体晶体在不同波长下改变光纤传输场分布.     

Hydrophobic photonic crystal fibers

We propose and demonstrate hydrophobic photonic crystal fibers (PCFs). A chemical surface treatment for making PCFs hydrophobic is introduced. This repels water from the holes of PCFs, so that their optical properties remain unchanged even when they are immersed in water. The combination of a hollow core and a water-repellent inner surface of the hydrophobic PCF provides an ultracompact dissolved-gas sensor element, which is demonstrated for the sensing of dissolved ammonia gas.     

胶体晶体微结构光纤传输特性研究

介绍了胶体晶体微结构光纤的结构, 采用时域有限差分法研究了微结构胶体晶体光纤的传输特性. 建立了该结构的FDTD模型, 计算了其透射谱和不同波长的传输场分布. 搭建了光学系统, 测量了实验制备的胶体晶体微结构光纤的透射谱, 并将其与模拟所得透射谱进行比较, 具有良好的一致性. 胶体晶体微结构光纤的传输场分布结果表明, 胶体晶体在不同波长下改变光纤传输场分布.     

Influence of the core size on light propagation in photonic liquid crystal fibers

In this paper analyses of mode distribution, confinement and experimental losses of the photonic crystal fibers with different core sizes infiltrated with liquid crystal are presented. Four types of fibers are compared: with single-, seven-, nineteen- and thirty seven solid rods forming the core in the same hexagonal lattice of seven “rings” of unit cells (rods or capillaries). The experimental results confirming the influence of the core diameter on light propagation are also included. The diameter of cores determines not only the number of modes in the photonic liquid crystal fiber but also is correlated with experimentally observed attenuation. For fibers with larger cores confinement losses are expected to be higher, but the measured attenuation is smaller because the impact of liquid crystal material losses and scattering is smaller.     

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     

有效折射率微扰法研究单缺陷光子晶体平板微腔的性质

应用有效折射率微扰法结合二维/三维平面波方法研究了施主和受主缺陷型H1微腔的性质, 使用修正后的有效折射率可以准确地计算微腔的腔模频率, 与三维全矢量时域有限差分法的计算结果很相近. 对于施主型H1微腔, 以介质带边为匹配标准修正的有效折射率计算的微腔腔模频率误差最小, 而对于受主型H1微腔, 匹配标准则应设置为中间带. 有效折射率微扰法既可以将计算的维度从三维降到二维, 大大减少计算所需的计算机内存和时间, 又可以保持计算结果的准确性, 这对于光子晶体微腔的广泛应用具有非常重要的价值.