Highly birefringent photonic crystal fiber with low confinement loss at wavelength 1.55 μm

High birefringent and low confinement loss of photonic crystal fiber is reported at wavelength 1.55 μm via Full-Vectorial Finite Element Method (FV-FEM). By suitable designing of three ring hexagonal solid core fiber and also by introducing a pair of large holes along x-axis near the core region, high modal birefringence 3 × 10⁻³ and low confinement loss 0.019 dB/km are found at wavelength 1.55 μm.     

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.     

Highly birefringent soft glass rectangular photonic crystal fibers with elliptical holes

In this paper we report on the fabrication of highly birefringent photonic crystal fiber with a photonic cladding composed of elliptical holes ordered in a rectangular lattice. The fiber features a group birefringence G of 0.82×10^?4 at 725 nm. We discuss the influence of structural parameters including the ellipticity of the air holes and the aspect ratio of the rectangular lattice on the birefringence and on the modal properties of the fiber.     

Temperature and pressure sensitivities of the highly birefringent photonic crystal fiber with core asymmetry

We investigated a particular design of a highly birefringent PCF with attractive features for pressure sensing applications. A plane-wave method together with the finite element method were used to numerically calculate phase and group modal birefringence, pressure and temperature sensitivities of our fiber. The simulation results together with the experiments demonstrate a considerable difference between a very high phase birefringence (B ∼ 10⁻³) and a very low negative group birefringence (G −10⁻³). Our fiber exhibits a low and positive temperature sensitivity (K_T < 0.1 rad/(K⋅m)), and relatively high and negative mechanical (pressure) sensitivity (K_p ≤ −10 rad/(MPa⋅m)), which supports its possible use as a mechanical sensor that does not require any temperature compensation.     

Highly nonlinear birefringent photonic crystal fiber

We propose an index guiding highly nonlinear birefringent photonic crystal fiber (PCF). Using a full vectorial finite element method (FEM), we investigate the key propagation characteristics of the proposed design. We demonstrate that it is possible to design a simple PCF structure configuration with a birefringence in the order of 10⁻² and a nonlinear coefficient of 49 W⁻¹ km⁻¹ at the wavelength of 1.55 μm. It is demonstrated that two zero dispersion wavelengths can be achieved by the proposed design. Bending analysis and fabrication issues are also discussed thoroughly.     

Highly Birefringent Honeycomb Photonic Bandgap Fibre

A new structure of highly birefringent honeycomb photonic bandgap fibres （PBGFs）, including an elliptical air hole in its solid core, is proposed and analysed by using full vectorial plane wave expansion method. From the numerical results it is confirmed that the proposed PBGF. has birefringence of the order of 10^-3. Moreover, there are two single-polarization single-mode ranges at varying normalized wavelength, in one of which only the slowaxis mode exists, and in the other only the fast-axis mode exists, which has not been achieved in index-guiding photonic crystal fibres so far.     

中红外高双折射高非线性宽带正常色散As2 S3光子晶体光纤

设计了一种中红外As₂S₃光子晶体光纤,利用多极法研究了这种光纤的双折射、色散和非线性特性.数值研究发现,该光纤在中红外波段λ = 3.625 μm处双折射B高达0.098;其x偏振方向的非线性系数γ_x达到了1.69 m^-1 ·W^-1, y偏振方向的非线性系数γ_y达到了0.78 m^{- 关键词： 光子晶体光纤 中红外波段 双折射 非线性}     

Highly birefringent octagonal photonic crystal fibers with two zero-dispersion wavelengths

A new highly birefringent octagonal photonic crystal fiber(Hi-Bi OPCF) with a rectangular array of four elliptical airholes in the fiber core region is proposed and analyzed using the full-vector finite element method with anisotropic perfect match layer absorbing boundaries.Numerical results show that the phase birefringence of the photonic crystal fiber(PCF) reaches 3.43×10-2 at the wavelength of 1 550 nm.Moreover,two zero-dispersion wavelengths are achieved in the visible and near infrared wavelength regions for one polarization state but not in the other.     

Analysis of a highly birefringent photonic crystal fiber with ellipse–rhombus air core

A novel highly birefringent photonic crystal fiber with small effective mode area is proposed. Four elliptical air-holes are designed in the internal layer of the fiber to cause the anisotropy, and the fiber has the property of highly birefringence and small effective mode area. The influences of elliptical air-holes on effective index, birefringence, effective mode area and nonlinear coefficient are analyzed by using full-vector finite element method (FEM). Simulation results show the birefringence can achieve the magnitude of 10⁻³ under the condition of d > 2.3 μm and a > 1.4 μm, which d and a are the distance and semimajor axis of elliptical air holes. By adjusting the parameters d and a, different effective mode area and nonlinear coefficient can be obtained, which demonstrates the flexibility of the proposed photonic crystal fiber.     

Measurement of the spectral dispersion curves of low birefringence polymer fibres

A method is suggested to overcome the difficulties of measuring the spectral dispersion of low birefringence fibres, that produce small optical path difference, δ<3λ, where δ is the optical path difference and λ is the wavelength of light used. This method depends on variable wavelength interferometry (VAWI). The suggested method is used to measure the spectral dispersion of birefringence of polypropylene fibre with a draw ratio 4 (low birefringence fibre). This method is also used to measure the spectral dispersion of birefringence of a polyester staple from ICI (high birefringence fibre). Also, the conventional VAWI method is used to measure the spectral dispersion of this fibre to confirm the results obtained by the suggested method. Microinterferograms are given for illustration.     

低损宽频高双折射太赫兹光子带隙光纤

设计了一种低损耗、宽频段、高双折射太赫兹光子带隙光纤,呈三角晶格排列的亚波长空气孔包层实现了带隙的局域作用.利用全矢量有限元法对光纤的双折射及损耗特性进行了理论分析.结果表明,在大约0.3 THz的宽频范围内,类矩形纤芯太赫兹光子带隙光纤的损耗小于0.009 cm^-1,相双折射在10^-3数量级,群双折射可达10^-2数量级. 关键词： 太赫兹 太赫兹波导 光子晶体光纤 双折射     

Highly birefringent photonic crystal fibers with flattened dispersion and low effective mode area

A highly birefringent index-guiding photonic crystal fibers with flattened dispersion and low effective area is proposed by introducing elliptical air holes in the cladding and small holes both in the core area and in the cladding. With the plane wave expansion (PWE) method, the birefringent, dispersion and effective area of the fundamental modes in such photonic crystal fibers are analyzed in detail. The simulation result shows that high birefringence with a magnitude of the order of 10⁻³, flattened chromatic dispersion from 1100 nm to 1800 nm and low effective area (which mean high nonlinearity) are obtained. Furthermore, the influences on the birefringence and dispersion by geometrical parameters have also been discussed and a modest number of design parameters are given.     

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.     

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.     

基于低双折射光子晶体光纤Sagnac干涉仪的超低温度系数扭曲传感器

研究了低双折射光子晶体光纤中由光纤扭曲造成的圆双折射效应,并应用Sagnac干涉仪结构设计了扭曲传感器.在Sagnac环中的光子晶体光纤上施加机械压力引入初始线双折射并产生正弦干涉光谱,再扭曲光纤产生圆双折射使干涉光谱随扭曲角度移动.光谱峰值波长随扭曲角度变化符合Sinc函数关系,理论分析与实验相符.传感器灵敏度为1.00 nm/°,分比率为0.01°,并具有超低的温度系数-0.5 pm/℃.     

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     

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.     

一种新型高双折射光子晶体光纤特性研究

设计了一种高双折射高非线性光子晶体光纤, 采用全矢量有限元法研究了这种光纤的基模模场、双折射、非线性、有效模面积及色散特性. 数值研究发现, 减小孔间距Λ的大小, 在波长1550 nm 处, 该光纤可获得10^-2 数量级的双折射B, 比普通的椭圆保偏光纤高约两个数量级; 同时, 该光纤可获得42 W^-1·km^-1 的高非线性系数γ. 另外,分别在可见光和近红外波段出现了两个零色散波长, 在波长800–2000 nm 之间具有良好的色散平坦特性. 这种设计为获得高双折射高非线性超平坦色散光子晶体光纤提供了一种新的方法, 该光纤在偏振控制、非线性光学和色散控制方面具有广泛的应用前景. 关键词： 光子晶体光纤 高双折射 高非线性 有限元法     

Highly birefringent photonic crystal fiber polarization splitter made of soft glass

A soft glass dual core polarization splitter based on highly birefringent photonic crystal fiber (PCF) is proposed and the full vector finite element method (FEM) is employed to analyze the impacts of structural parameters on birefringence and the coupling length, and simulation results show that high birefringence on the order of 10⁻² can be obtained at 1.55 μm, moreover, hole size, hole pitch and elliptic ratio all affect birefringence and the coupling length. Based on these results, the PCF's structure is optimized to realize a polarization splitter of 282 μm whose largest extinction ratio is around −45.42 dB at 1.55 μm. Meanwhile, the bandwidth at the extinction ratio of −10 dB is about 90 nm, and around 32 nm at −20 dB.     

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