八角光子晶体光纤传输特性与非线性特性研究

基于有限元法对一种全内反射型八角光子晶体光纤的传输特性和非线性特性进行了研究,并改变该光子晶体光纤空气孔结构参数得出了其特性与光波长的曲线关系图. 最终得到一种新结构光子晶体光纤,在入射光波长为1.55 μm低损耗窗口处具有非常优越的传输特性和较平坦非线性特性. 关键词： 光子晶体光纤 色散 损耗 非线性系数     

光子晶体光纤非线性系数的数值计算

针对全反射型光子晶体光纤在短波长处的横向电场分布特点，在忽略空气孔内极为微小的电场影响下，将光纤等效为阶跃型光纤，导出一种新的计算有效折射率的方法.结合Sellmeier公式推出光子晶体光纤的非线性系数与其两个几何结构参量和波长的简洁解析关系.对非线性系数随着这些参量的变化进行了数值计算与讨论，得出非线性随着空气孔直径或空气孔直径与孔间距比d/Λ值的增大成指数上升的规律.在波长为0.55 μm和0.85 μm时，非线性系数分别可高达3.5和2.54 m－1W－1.     

高非线性光子晶体光纤色散特性的研究

采用矢量光束传输法对不同结构参量的高非线性光子晶体光纤的非线性特性和色散特性进行了数值分析,计算得出高非线性光子晶体光纤的物理参量基模有效面积Aeff 、非线性系数γ和色散系数D.分析了Aeff 、γ和D与高非线性光子晶体光纤结构参量空气孔间距Λ、空气孔直径d之间的关系.分析结果表明,通过调节光子晶体光纤的结构参量可以灵活地调整高非线性光子晶体光纤的非线性特性和色散特性.     

光子晶体光纤数值孔径的测量和数值研究

光纤的数值孔径是光纤的重要参数,大数值孔径光纤在激光器和激光感应荧光系统中有很好的应用前景。光子晶体光纤的数值孔径与传统阶跃型光纤不同,它与光波长有密切的关系。因此,本文用光谱仪测量了不同结构的折射率引导型光子晶体光纤的数值孔径,并进行了数值模拟,研究了光波长、包层空气孔直径、孔间距等对光子晶体光纤数值孔径的影响,同时对光子晶体光纤的非线性系数、宏弯损耗、截止波长、有效模面积等与光波长有关的参数进行了研究,取得了满意的结果。     

高双折射光子晶体光纤研究

设计了一种高双折射光子晶体光纤(Photonic Crystal Fiber,PCF),即增大两个与纤芯相邻的空气孔直径,使光纤只具有二重对称性,呈现出较高的双折射.通过压缩x轴方向孔间距,进一步增大双折射度.采用全矢量有限单元法(Finite-element Method,FEM),研究了该光子晶体光纤基模对应的相双折射和群双折射,给出了该高双折射PCF双折射随输入光波长的变化曲线.结果获得了10－3量级的高双折射.具有设计参量的该光子晶体光纤结构的相双折射在1 550 nm处可以达到5.0×10－3,在更长的波长处,这一值会更高.     

C6v对称TIR-PCF结构参量对基模非线性系数的影响数值研究

用多极方法数值研究构成六重对称(C6v)全内反射型光子晶体光纤(TIR-PCF)各种结构参量对波长在1.55 μm基模非线性系数的影响.数值结果表明包层空气孔层数、空气孔直径、间距、相对孔径对基模非线性系数都有不同程度的影响,其中空气孔层数的影响较小,在其它参量不变时波长越大基模非线性系数越小.层数与间距一定在波长1.55 μm时包层空气孔直径越大基模非线性系数越大,层数与包层空气孔直径一定时间距越大（相对孔径越小）基模非线性系数越大,在层数与相对孔径一定时基模有效面积随空气孔半径与间距的同比增大而减小.     

高功率光纤激光器全内反射型大模场光子晶体光纤设计

在高功率密度下产生的非线性效应和材料损伤等问题限制了光纤激光器输出功率的进一步提高。利用大模场光纤降低光纤能量密度,提高非线性阈值是一种最为直接和有效的手段。以空气孔尺寸为光波长量级的全内反射型光子晶体光纤为对象,采用等效折射率模型分析了光子晶体光纤的单模特性,利用有限元法分析了结构参数对光子晶体光纤的模场面积和色散等光束质量参数的影响。设计了一种工作波长为0.40~1.55μm,模场面积为112.74~258.87μm2,且在1.27μm附近可补偿色散的大模场光子晶体光纤。该研究可为高功率光纤激光器大模场光纤的进一步参数优化设计及元件加工提供重要参考。     

改进型蜂巢晶格结构光子晶体光纤的色散与非线性特性

结合蜂巢晶格与不同空气孔直径晶格二者的优势,提出一种改进犁蜂巢晶格结构光子晶体光纤,采用矢量光束传输法对该光纤的色散与非线性特性进行了数值模拟,分析了色散、非线性系数与其晶格参量之间的关系.数值结果表明,该光纤在1.2～1.6 μm波段内可以实现大负色散、色散平坦、正色散等多种色散特性;此外,晶格结构中空气孔直径的减小...     

光子晶体光纤接续损耗的理论分析

基于超格子构造法,采用全矢量模型计算了光子晶体光纤的模场半径,由此出发理论分析了光子晶体光纤与普通单模光纤之间接续损耗分别受横向偏移、轴向倾斜以及模场不匹配的影响,给出了光子晶体光纤在部分常用结构参量区域{Λ,d/Λ}内与SMF-28接续损耗的理论值,讨论了光子晶体光纤各结构参量与接续损耗之间的关系。并简要分析了不同结构光子晶体光纤之间的接续损耗。结果表明,接续损耗对横向偏移和轴向倾斜都非常敏感;孔距是决定接续损耗大小最主要的因素;与普通单模光纤接续,当光子晶体光纤的孔距比该单模光纤纤芯半径大一些时,接续损耗比较小;两种不同结构光子晶体光纤之间的接续损耗大小最主要取决于它们孔距的差异。     

光子晶体光纤

近几年来，光纤家族又增添了一个新的成员——光子晶体光纤。该光纤对于传统意义的光纤而言，其传输机理有着本质上的差别，因而无论是在通信领域还是在光纤传感领域，都引起了人们极大的兴趣。并被誉为下一代光纤。具有微观结构是光子晶体光纤的主要特点。按照传光机理，通常将光子晶体光纤分为两类：全内反射效应型和光子带隙效应型。本文简要的介绍并讨论了这两种光子晶体光纤有别于谱通光纤的基本特性。     

Polarization maintaining large nonlinear coefficient photonic crystal fibers using rotational hybrid cladding

In this paper, we present and explore a new hybrid cladding design for improved birefringence and highly nonlinear photonic crystal fibers (PCFs) in a broad range of wavelength bands. The birefringence of the fundamental mode in such a PCF is numerically analyzed using the finite element method (FEM). It is demonstrated that it is possible to design a simple highly nonlinear hybrid PCF (HyPCF) with a nonlinear coefficient of the about 46 W⁻¹ km⁻¹ at a 1.55 μm wavelength. According to simulation, the highest modal birefringence and lowest confinement loss of our proposed structure at the excitation wavelength of λ = 1.55 μm can be achieved at a magnitude of 1.77 × 10⁻² and of the order less than 10² dB/km with only five rings of air-holes in the fiber cladding.     

基于纤芯折射率增强的高双折射光子晶体光纤

通过增加光纤纤芯区域折射率实现了一种高双折射光子晶体光纤.采用全矢量有限元和平面波展开方法，系统地研究了这种高双折射光子晶体光纤在不同的高折射率区域参数(比如区域形状、折射率)情况下的光纤特性.模拟结果表明,光子晶体光纤的双折射可以在优化的参数条件下获得很大提高，光子晶体光纤的非线性系数(连同双折射)也可以同时得到提高.     

Analysis of high birefringence photonic crystal fiber with octagonal and squarely lattice

Aiming at the requirement of high birefringence, a new kind of photonic crystal fiber (PCF) with octagonal and squarely lattice is proposed. In this structure, squarely lattices are added in the inner layer to obtain high birefringence. Birefringence and dispersion as a function of wavelength and size of PCF are analyzed by using Finite Element Method (FEM). Simulation results show that this kind of PCF exhibits high birefringence with a magnitude of 10^?3, and one zero dispersion point is obtained simultaneously. In addition, the characteristics of PCF can be tuned by changing the size of fiber.     

Room temperature multiwavelength erbium-doped fiber ring laser using a highly nonlinear photonic crystal fiber

A multiwavelength laser source is demonstrated with a high power erbium-doped fiber amplifier as the gain medium. A highly nonlinear photonic crystal fiber (PCF) is inserted in the ring cavity to provide nonlinear gain by four-wave mixing. A Sagnac loop is incorporated in the ring cavity serving as a comb-like multichannel filter. The comparison between fiber ring laser without PCF and with PCF shows that the highly nonlinear PCF can generate a larger number of excited wavelengths and help stabilize the output power.     

八边形高双折射双零色散点光子晶体光纤特性分析

针对光纤通信和传感系统中高双折射、多零色散点的应用需求, 设计了一种新型结构的光子晶体光纤.该结构包层为圆形空气孔按照八边形形状排列而成, 并在内包层对称位置中加入两个椭圆空气孔以获得高双折射特性. 通过有限元数值分析方法对光纤特性进行分析,仿真结果表明,该结构光子晶体光纤在波长0.8—2 μm 范围内双折射可达10^-3量级,满足高双折射的应用需求,并且满足两个零色散点的应用需求. 同时光纤的非线性系数达10^-2·m^-1·W^-1量级,可应用于对非线性要求较高的场合.     

Novel single-mode and polarization maintaining photonic crystal fiber

In this paper, we present and propose a novel structure for improved birefringence and single-mode propagation condition photonic crystal fiber (PCF) in a broad range of wavelength. The birefringence of the fundamental mode and single mode property in such a PCF is numerically estimated by employing full vector finite element method (FVFEM) and anisotropic perfectly matched layers (APML). The simulation results illustrate that we can achieve a high birefringence and perfect single-mode condition by employing silica-filled into one-line elliptical air holes parallel to x-axis and rotated by an angle. Obviously, the proposed PCF is quite useful for optical devices.     

Design of highly birefringent chalcogenide glass PCF: A simplest design

In this article, a new simplified structure of a highly birefringent chalcogenide As₂Se₃ glass photonic crystal fiber (PCF) is designed and analyzed by using fully vectorial finite element method. The effective indices, confinement loss, birefringence, and chromatic dispersion of fundamental polarized mode are calculated in the proposed PCF for a wide wavelength range. To maintain the polarization in chalcogenide As₂Se₃ glass PCF, we enlarged two of the central air holes and reduced two transverse air holes for achieving high birefringence. This helps in creating an effective index difference between the two orthogonal polarization modes. It is also shown that As₂Se₃ glass PCF provides lower chromatic dispersion and less confinement loss compared to silica PCF of the same structure in wavelength range 1.3 to 1.8 μm and hence such chalcogenide As₂Se₃ glass PCF have high potential to be used in dispersion compensating and birefringence application in optical communication systems. In addition to this, the polarization mode dispersion (PMD) result of the proposed PCF is also reported.     

Simultaneous strain and temperature measurement using a highly birefringence fiber loop mirror and a long-period grating written in a photonic crystal fiber

We present a new design for simultaneous strain and temperature measurement using a high-birefringence fiber loop mirror (HiBi-FLM) concatenated with a temperature-insensitive long-period grating (LPG) written in a photonic crystal fiber (PCF). The FLM acts as a sensor head, while the LPG in PCF serves as a filter to convert wavelength variation to optical power change. By measuring the wavelength variation and the power difference of two near peaks in the spectral response of this configuration, simultaneous strain and temperature measurement is obtained.