高压力光子晶体光纤传感器系统的研究

光子晶体光纤(PCF)压力传感器可广泛用于各种环境压力监测中.采用全矢量有限元方法对双芯光子晶体光纤的双折射特性进行了分析,采用二阶微分方程理论模型模拟了光子品体光纤高压力传感器对外界压力的响应,并应用这个模型讨论了外界压力作用对敏感元件有效折射率和双折射的影响,提出了一种高压力光子晶体光纤传感器方案.计算结果表明高压力致双空气孔芯光子晶体光纤的双折射值可达很高,光子晶体光纤传感器系统更为简洁紧凑.     

一种Sagnac干涉仪结构的光子晶体光纤温度传感器

采用Sagnac干涉仪结构,设计了一种高双折射光子晶体光纤环镜温度传感器。光子晶体光纤温度稳定性好,通过向高双折射光子晶体光纤空气孔填充热光系数高的液体材料乙醇,从而实现温度传感的目的。采用平面波展开法,分析了高双折射光子晶体光纤的双折射与传输波长和温度的关系。理论分析表明,填充乙醇后,高双折射光子晶体光纤的双折射随着传输波长和温度的增加而增加,且双折射与温度成线性关系。实验中将一段填充乙醇的高双折射光子晶体光纤与3 dB耦合器熔接制作成Sagnac干涉仪结构的光纤环镜,当温度从 45 ℃升至80 ℃时,光谱仪上观察到凹点λi向短波方向漂移了309.280 nm,温度灵敏度高达8.837 nm/℃。     

光子晶体光纤的现状和发展

光子晶体光纤(PCFs)具有很多在传统光纤中无法实现的特性,成为近些年光学和光电子学的研究热点.对光子晶体光纤十几年的发展历史进行了简要的回顾,介绍了光子晶体光纤领域中的一些基本概念,光子晶体光纤的分类及光子晶体光纤的制备工艺.重点论述了光子晶体光纤的无限截止单模传输特性,可调节的色散特性,大模面积特性,高双折射特性和高非线性特性及其在非线性光学和光子晶体光纤激光器等方面的应用,并对发展前景进行了展望.     

高双折射光子晶体保偏光纤研究进展

光子晶体光纤的问世,使得光子晶体保偏光纤(Polarization maintained photonic crystal fibers,PM-PCF)的研究一直是光通信领域的研究热点.在综述国内外大量文献的基础上,对高双折射光子晶体保偏光纤的传输机理和保偏原理进行分析,评述了高双折射光子晶体保偏光纤的各种设计方案,并进一步对光子晶体保偏光纤的研究现状、应用和发展前景进行了展望.     

光子晶体光纤

全面介绍了光子晶体光纤的最新实验和理论进展，探讨了光子晶体光纤、尤其是高双折射光子晶体光纤的应用前景。     

光子晶体光纤的导光原理、特性、应用及研究方向

与普通光纤相比，光子晶体光纤具有无休止单模传输、极大的色散、高双折射和极好的光学非线性等特性，因此近年来受到人们的广泛关注。简要介绍了光子晶体光纤的导光原理、特性、应用及研究方向。     

光子晶体光纤的设计与应用研究综述

光子晶体光纤具有较强的可设计性,一般通过改变光子晶体光纤包层中空气孔的大小、形状或者排列方式对光纤的传输特性进行调节,以此实现高双折射、高非线性、平坦色散及低限制性损耗等特性。光子晶体光纤的传输特性在不同领域中具有较大的应用价值,如分布式传感、飞秒激光器和气体传感器等。文章首先介绍了光子晶体光纤的结构特征以及与普通单模光纤的区别,在此基础上针对各种典型的光子晶体光纤结构分析了其色散和非线性等传输特性。详细介绍了基于光子晶体光纤的分布式光纤传感、飞秒激光器和气体传感器的传感机理以及达到的传感性能,并与非基于光子晶体光纤的传感器的传感性能进行了比较,验证了基于光子晶体光纤传感器的优异性能。最后对光子晶体光纤的发展及应用进行了总结与展望。     

椭圆孔六角点阵聚合物光子晶体光纤的偏振特性研究

基于全矢量平面波方法,以聚甲基丙烯酸甲酯为基材,设计了一种高双折射光子晶体光纤,并对其传输性质和偏振特性进行了数值模拟。结果表明,椭圆孔六角点阵聚合物光子晶体光纤的双折射是由于包层的不对称性引起的全局双折射,通过调节椭圆率,发现该光纤可以以单模方式在一合适波段运行,该波段与聚合物光纤的低损耗通信窗口一致。并且在 时,其双折射最高可达 。该研究结果为高双折射聚合物光子晶体保偏光纤的制备提供了理论依据。     

一种新型混合包层结构高双折射光子晶体光纤

针对光子晶体光纤中高双折射的应用需求,提出了一种基于全内反射导光机制的新型混合包层结构光子晶体光纤,采用全矢量有限元法分析了结构参数对该光纤双折射的影响,以及采用全矢量有限元软件对该光纤结构进行了仿真。仿真结果表明,通过调整包层椭圆孔的椭圆率和孔间距等参数,该结构的光子晶体光纤在1.55 μm波长处可实现10-2量级的高双折射。     

高对称性模场分布的高双折射光子晶体光纤

设计了一种具有高对称性模场分布的高双折射光子晶体光纤(PCF)结构,由尺寸相同的椭圆空气孔菱形排列组成。利用全矢量有限元法对该种结构光子晶体光纤的基模场分布、有效模场面积、双折射和色散进行数值分析,所得结果与相同结构参数的圆形空气孔光子晶体光纤进行比较。这两种光纤的模场均具有高对称性,近似圆形,并且易于与光器件中其他光纤耦合。椭圆空气孔光子晶体光纤的双折射可达10-3。     

Birefringence Characteristics of Squeezed Lattice Photonic Crystal Fibers

By using the supercell lattice method, we investigate the influence of the squeezing lattice on the birefringence characteristics of photonic crystal fibers (PCFs). We first define the concept of squeezing ratio and then present a model, with which several types of PCFs are simulated. Simulation results show that the squeezing of PCFs' lattice with the uniform air holes in the cladding can break the multifold symmetry of PCFs and make PCFs highly birefringent. Furthermore, it is reported for the first time to our knowledge that the polarity of PCFs' birefringence can change several times as the air-hole diameter changes.     

Highly birefringent index-guiding photonic crystal fibers

Photonic crystal fibers (PCFs) offer new possibilities of realizing highly birefringent fibers due to a higher intrinsic index contrast compared to conventional fibers. In this letter, we analyze theoretically the levels of birefringence that can be expected using relatively simple PCF designs. While extremely high degrees of birefringence may be obtained for the fibers, we demonstrate that careful design with respect to multimode behavior must be performed. We further discuss the cutoff properties of birefringent PCFs and present experimental results in agreement with theoretical predictions on both single- and multimode behavior and on levels of birefringence     

Highly Birefringent Photonic Crystal Fibers With Ultralow Chromatic Dispersion and Low Confinement Losses

Highly birefringent photonic crystal fibers (PCFs) with low confinement loss with ultralow and ultraflattened chromatic dispersions at wide wavelength band are presented. The transverse electric field vector distributions of two linearly polarized fundamental modes, their effective indices, modal birefringence, confinement losses and chromatic dispersion of the proposed PCFs are reported by using full-vector finite-element method (FEM). Significant improvements of PCFs in terms of the birefringence, chromatic dispersion and confinement losses are demonstrated by careful investigation of all air holes in each ring, air holes diameters and hole-to-hole spacing. In addition to this, the polarization beat length results of the proposed PCFs are also reported and discussed thoroughly.     

A kind of photonic crystal fiber with high birefringence and low cofinement loss

The triangular-lattice highly birefringent photonic crystal fibers（PCFs） with gradually increasing diameter of the air holes along radial axis are put forward. The modal birefringence, dispersion and confinement loss of the fundamental mode are simulated by full vector Galerkin finite element method（FEM） with a perfectly matched layer（PML）. The results show that this PCF can keep low confinement loss when the rings of air holes are few. When the wavelength is 1.55 μm, the birefringence, the confinement loss of quick-axis and slow-axis are 1.365×10^-3, 0.017 dB/m and 0.051 dB/m, respectively. A new way is proposed to fabricate polarization-mainting fibers with high performance.     

PCF-based polarization splitters with simplified structures

We propose novel polarization splitters based on photonic crystal fibers (PCFs), in which the cores of the splitters are nearly nonbirefringent. Different from conventional fiber-based polarization splitters, the birefringence in the new splitters results mainly from narrow silica regions physically connecting the two cores. This means that polarization splitting can be achieved without employing highly birefringent cores, which provides a possibility to greatly simplify the structures of the PCF-based polarization splitters and make them more practical. A 5-mm-long splitter with an extinction ratio of 20 dB has been obtained. We also discuss how the silica regions influence coupling characteristics of the dual-core PCFs and present a design guidance for the polarization splitters based on polarization-dependent coupling.     

Design of low-confinement-loss and highly birefringent index-guiding photonic crystal fibers

We present a systematic scheme to achieve both high birefringence and low confinement loss in index-guiding photonic crystal fibers （PCFs）, using a structurally-simple PCF with finite number of air holes in the cladding region. By increasing the size of the outermost-ring air holes in the cladding region, highly birefringent PCFs with low confinement loss can be successfully achieved. The design strategy is based on the fact that the modal birefringence of PCFs is dominated by the inner-ring air holes in PCF, which is verified by a full-vector finite element method with anisotropic perfectly matched layers. Numerical results show that modal birefringence in the order of 10-3 and confinement loss less than 0.1 dB/km can be easily realized in the proposed PCF with only four rings of air holes in the cladding region. We expect that such fibers will be much easier to be fabvicated than those with more air holes in the cladding region.     

Polarization-dependent coupling in twin-core photonic crystal fibers

The polarization dependence of light coupling in photonic crystal fibers (PCFs) with sixfold symmetric dual cores and highly birefringent dual cores are numerically investigated. The characteristics of PCF-based couplers, such as coupling length, extinction ratio and form birefringence, are examined as functions of the air-hole size and pitch. The silica bridges between air holes take an important role in the energy transfer across the two cores. We believe that the mechanism of light coupling in PCF-based couplers is different from that of conventional waveguide couplers. The polarization dependent coupling can be reduced by adjusting the air holes around the cores of PCFs. On the other hand, the polarization dependent coupling can be enhanced by introducing high birefringence in the two cores.     

A novel polarization splitter based on the photonic crystal fiber with nonidentical dual cores

A novel polarization splitter based on photonic crystal fibers (PCFs) with two nonidentical cores is proposed. The two highly birefringent cores are vertically arranged to obtain polarization selective coupling. The horizontal polarization exchanges its energy between the two cores. However, the vertical polarization shows little coupling between the two cores. This is achieved in single-material glass waveguides for the first time to our knowledge. The PCF-based polarization splitter exhibits many advantages such as shorter length, high extinction ratio, and wide bandwidth over its counterparts.     

光子晶体光纤非线性光学研究新进展

光子晶体光纤(PCF),又称为多孔光纤(HF)或微结构光纤(MF),是一种单一介质,并由波长量级的空气孔构成微结构包层的新型光纤。光子晶体光纤呈现出许多在传统光纤中难以实现的特性,从1996年世界上制造出第一根光子晶体光纤以来,它便受到了广泛关注并成为近年来光学与光电子学研究的一个热点。介绍了光子晶体光纤的制作工艺、工作原理、基本特性、目前的研究重点和进展情况,重点评述了光子晶体光纤非线性光学方面的研究及其潜在的应用。     

Dependence of birefringence on elliptical-hole orientation in photonic crystal fibers

In this paper, the dependence of birefringence on the orientation of elliptical holes in triangular-lattice elliptical-hole photonic crystal fibers (PCFs) is investigated numerically. A resonant enhancement of birefringence between the anisotropic lattice arrangement and oriented elliptical holes is observed, and the birefringence varies periodically with the elliptical-hole orientation. When the major axes of adjacent elliptical holes are parallel, the birefringence approaches the maximum. Based on the numeric analysis, a novel highly birefringent PCF is proposed, and the maximum modal birefringence of 0.086 is achieved.