Design of photonic crystal fiber with elliptical air-holes to achieve simultaneous high birefringence and nonlinearity

A new type of V-shaped photonic crystal fiber with elliptical air-holes is proposed to realize simultaneous high bire- fringence and nonlinearity at a wavelength of 1.55 μm. The full vector finite element method was adopted to investigate its characteristics, including birefringence, nonlinearity, and dispersion. The PCF exhibited a very high birefringence of 2.89x10-2 and very high nonlinear coefficient of 102.69 W-1 .km 1. In particular, there were two zero-dispersion wave- lengths （ZDWs） in the visible （X： 640-720 nm and Y： 730-760 nm） and near-infrared regions （X： 1050-1606 nm and Y： 850-1500 nm）. The combination of high birefringence and nonlinearity allowed the PCF to maintain the polarization state and generate a broadband super continuum, with potential applications in nonlinear optics.

Coupling characteristics of high birefringence dual-core As_2S_3 rectangular lattice photonic crystal fiber

A type of As2S3 chalcogenide glass mid-infrared dual-core photonic crystal fiber has been proposed. The dualcore photonic crystal fiber （PCF） consists of two asymmetric cores. The high polarization property and the coupling characteristics have been studied by using the finite dement method and mode coupling theory. Numerical results show that the birefringence at wavelength λ = 10 μm is up to 0.01386 and the coupling length can reach wavelength = 5 μm, 261 μm and 271.44 μm for x-polarized mode and y-polarized mode, respectively. It demonstrates that a 6.786-ram-long fiber can exhibit an extinction ratio of better than -10 dB and a bandwidth of 180 nm.

Designing of a polarization beam splitter for the wavelength of 1310 nm on dual-core photonic crystal fiber with high birefringence and double-zero dispersion

We have proposed a novel kind of photonic crystal fiber which contains two asymmetric cores. The bireti＇ingence and the dispersion are numerically analyzed based on finite element method when the size of the air holes and the pitch of two adjacent air holes are changed. It is shown that the proposed photonic crystal fiber has high birefringence up to the order of 10-2 and double-zero dispersion points are at the wavelengths of 1310 nm and 800 rim, simultaneously. At the same time, the normalized power and the extinction ratios of the proposed photonic crystal fiber have been simulated. It is demonstrated that, at the wavelength of 1310 rim, the x-polarized mode and the y-polarized mode are separated when the propagation distance is 2.481 ram.

High birefringence, low loss, and flattened dispersion photonic crystal fiber for terahertz application

A type of photonic crystal fiber based on Kagome lattice cladding and slot air holes in a rectangular core is investigated. Full vector finite element method is used to evaluate the modal and propagation properties of the designed fiber.High birefringence of 0.089 and low effective material loss of 0.055 cm^-1 are obtained at 1 THz. The y-polarized fundamental mode of the designed fiber shows a flattened and near-zero dispersion of 0±0.45 ps · THz^-1· cm^-1 within a broad frequency range(0.5 THz–1.5 THz). Our results provide the theory basis for applications of the designed fiber in terahertz polarization maintaining systems.

Reseach Progress of Photonic Crystal Fibers in China

Photonic Crystal Fibers have attracted worldwideinterest within the last decade due to their uniqueoptical properties and because they exhibit a muchhigher degree of design freedom compared to conventionaloptical fibers.In this article, the fabricationtechnologies of photonic crystal fibers and theirapplications at home and abroad were formulated atlength, especially in the following fields, such aslarge mode area active photonic crystal fibers andfiber lasers, birefringence fibers and sensors, highnonlinear photonic crystal fibers and frequencytransformation, dispersion compensation PCFs anddispersion compensation for telecommunicationsystems, and photonic band-gap fibers. Finally, accordingto the above analysis, the prospects anddeveloping trends of photonic crystal fibers in thefuture were presented.

Polarization characteristics of chiral photonic crystal fibers with an elliptical hollow core

The theoretical study of dielectric-chiral photonic crystal fiber （PCF） with an elliptical hollow core is presented. The band structure of chiral photonic crystal （PhC） is calculated by using a modified plane-wave expansion （PWE） method. By examining the out-of-plane photonic bandgaps （PBGs） of chiral PhC, a kind of chiral PCF with a hollow core is designed and their eigenstates are calculated. The distributions of mode field and polarization state are demonstrated, and how the structural asymmetry of the core together with the chirality in the background affects the modal polarization is discussed. The dependences of birefringence on chirality for different ellipticities of core are investigated.

Wavelength-selective characteristics of high birefringence photonic crystal fiber with Au nanowires selectively filled in the cladding air holes

Filter characteristics of a designed gold-filled high birefringence photonic crystal fiber are investigated based on the finite element method. The wavelength filter resonances in the high birefringence photonic crystal fiber occur at different points for different polarized directions, and the resonance strength in the x-polarized case is much weaker than that in the y-polarized case. The much more obvious splitting filter characteristics and different resonance strength imply the study and application values in splitting and single polarization fiber devices. The simulation results show that increasing the number of the gold wires only enhances the resonance strength when there is no surface plasmon supermode formed. With the diameters of the gold wires increasing, the response wavelength moves to a longer wavelength, and the strength becomes stronger. When the diameter is increased to 1.4 μm, the response wavelength in the x-polarized case can be tuned to 1.318 gin, which is the communication wavelength. The strongest resonance occurs at 1.2375 μm in the y-polarized case, and the peaking loss can reach 435.83 dB/cm.

Tunable and highly sensitive temperature sensor based on graphene photonic crystal fiber

Optical fiber temperature sensors have been widely employed in enormous areas ranging from electric power industry,medical treatment,ocean dynamics to aerospace.Recently,graphene optical fiber temperature sensors attract tremendous attention for their merits of simple structure and direct power detecting ability.However,these sensors based on transfer techniques still have limitations in the relatively low sensitivity or distortion of the transmission characteristics,due to the unsuitable Fermi level of graphene and the destruction of fiber structure,respectively.Here,we propose a tunable and highly sensitive temperature sensor based on graphene photonic crystal fiber(Gr-PCF)with the non-destructive integration of graphene into the holes of PCF.This hybrid structure promises the intact fiber structure and transmission mode,which efficiently enhances the temperature detection ability of graphene.From our simulation,we find that the temperature sensitivity can be electrically tuned over four orders of magnitude and achieve up to~3.34×10^(-3) dB/(cm·℃)when the graphene Fermi level is~35 meV higher than half the incident photon energy.Additionally,this sensitivity can be further improved by~10 times through optimizing the PCF structure(such as the fiber hole diameter)to enhance the light–matter interaction.Our results provide a new way for the design of the highly sensitive temperature sensors and broaden applications in all-fiber optoelectronic devices.

A Photonic Crystal Fiber Based Asymmetric Slotted Structured Highly Sensitive Refractive Index Plasmonic Biosensor

Surface plasmon resonance (SPR) sensors have grown in popularity owing to their sensitivity, precision, and capacity for a variety of applications, including detection, monitoring, and sensing, among others. Sensitivity and resolution are two areas where this technology has room for development. A plasmonic biosensor based on an asymmetric slotted PCF structure with extremely high sensitivity has been described and theoretically investigated. This high performance sensor is constructed and completely characterized using finite element method in COMSOL Multiphysics software environment. Sensitivity and resolution are analyzed as performance parameters for the proposed sensor. Numerical simulation exhibits the maximum wavelength-sensitivity of 1100 nm/RIU with 9.09 × 10-6 RIU resolution in the broad measurement range of refractive index from 1.30 to 1.44. A polarization controller can be used to fine-tune this extremely sensitive and wide-ranging refractive index sensor to fulfil a variety of practical needs. This is performed with the consideration of the variation in the refractive index (RI) of the analyte channels. In comparison with earlier PCF-based sensors, the fiber design structure is basic, symmetrical, simple to produce, and cost-effective. Because of the asymmetric air holes and higher sensitivities of the refractive index detector, it is possible to identify biomolecules, biochemicals and other analytes.

The polarization-dependent supercontinuum generation in photonic crystal fibers with high birefringence and two-zero dispersion

A polarization-dependent supercontinuum spectrum source of light from the UV to infrared region has been generated in our photonic crystal fiber with birefringence B=2.23×10 3.By tuning the polarization direction of the input pulse,it is found that the width of the supercontinuum spectrum changes dramatically with the input polarization directions.At the same time,we qualitatively explain the blue-shift peak and the red-shift peak in the experimental spectrum using phase matching conditions on dispersive waves,stoke waves and the pump wave.In addition,we also found that supercontinuum spectrum generation,to some extent,is dependent on the pump wavelength and average power of the pump.The spectrum is broadened with the increase of average power,but unchanged after average power reaches a certain value;when the pump wavelength is located in the anomalous dispersion and further away from the zero-dispersion wavelength,the spectrum of the supercontinuum is wider.

Ultra-broadband modulation instability gain characteristics in As_2S_3 and As_2Se_3 chalcogenide glass photonic crystal fiber

Based on the designed As2Se3 and As2S3 chalcogenide glass photonic crystal fiber（PCF） and the scalar nonlinear Schrdinger equation,the effects of pump power and wavelength on modulation instability（MI） gain are comprehensively studied in the abnormal dispersion regime of chalcogenide glass PCF.Owing to high Raman effect and high nonlinearity,ultra-broadband MI gain is obtained in chalcogenide glass PCF.By choosing the appropriate pump parameter,the MI gain bandwidth reaches 2738 nm for the As2Se3 glass PCF in the abnormal-dispersion region,while it is 1961 nm for the As2S3 glass PCF.

Numerical Study on Optical Solitons Transmission System with 40 Gbit/s in the Photonic Crystal Fiber

The 40 Gbit/s optical solitons transmission system in photonic crystal fiber was investigated by fast Fourier transform method, and the maximum transmission distance of system was calculated numerically. By the eye pattern of system, the transmission performances of system were studied. Results show that when polarization mode dispersion coefficient Dp is smaller than , the influence of the PMD on the transmission distance was neglectable. When the dispersion coefficient D is larger than 1.5 ps/km/nm, the transmission distance decreases rapidly. The positive or negative of three order group-velocity dispersion makes no differences on the system transmission.

Equal channel spacing Sagnac filter using high-birefringent photonic crystal fibers

An equal channel spacing Sagnac filter is proposed using a high-birefringent photonic crystal fiber （PCF） with birefringence square to the operation wavelength. A PCF with four smaller central air holes sur-rounded by larger air holes is applied in a Sagnac filter with optimized parameters to achieve equal channel spacing of 0.8 nm. Given that the birefringence of this PCF is square to the operation wavelength, the channel spacing of the proposed filter changes by only 0.03 nm within a wavelength range from 1400 to 1650 nm; this is about one order of magnitude less than that constructed with conventional high-birefringent fibers.

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.

Highly Birefringent Photonic Crystal Fibers B Using Asymmetric Core Design

We demonstrate a highly birefringent photonic crystal fiber by utilizing the asymmetric core design. Based on spectral measurements of the polarization mode interfering, we estimate that the fiber has a beat length of about 0.33 mm at 1545 nm.

高双折射椭圆纤芯类矩形排布光子晶体光纤的性能研究

高双折射光子晶体光纤具有较强的线偏振光保持能力,采用Bi_(2)O_(3)-GeO_(2)-Ga_(2)O_(3)多组分激光玻璃材料作为纤芯设计了独特结构的高双折射光子晶体光纤。运用有限元法结合完美边界条件,得出该光子晶体光纤在1.55μm和1.80μm波长下,双折射系数分别为5.207×10^(-2)和6.882×10^(-2)。在1.55μm波长处,X和Y极化方向的限制损耗分别为1.386×10^(-5)dB/km和5.386×10^(-7)dB/km。非线性系数表明,结构参数M(D/Λ)分别为0.7和0.8的光子晶体光纤,非线性系数在X和Y极化方向上,范围分别在4.374×10^(3)-4.906×10^(3)km^(-1)·W^(-1)和5.621×10^(3)-6.978×10^(3)km^(-1)·W^(-1)之间。本文所设计的高双折射光子晶体光纤的独特结构和优异性能特点,为光通信和光传感等应用领域提供了新的解决方案。

基于高双折射侧边抛磨光子晶体光纤的表面等离激元共振双参量传感器

利用表面等离激元共振(SPR)技术设计了一款高双折射光子晶体光纤(PCF)传感器,可以实现宽范围的双参量高灵敏度传感.采用侧边抛磨的结构,内部空气孔呈三角晶格排列.金纳米层涂覆在抛磨面直接与待测物接触作为测量折射率RI的通道,更加方便检测工作的进行,靠近纤芯的椭圆孔内充满氯仿用来探测温度.两个独立的通道以及由非对称引入的双折射可以确保独自测量折射率和温度的变化,解决了交叉灵敏度问题.借助全矢量有限元软件COMSOL Multiphysics,灵活使用散射边界条件可以很好的对光子晶体光纤传感器的光学特性进行数值分析研究.实验结果表明,文中提出的传感器可以测量折射率范围为1.32~1.39,温度范围是20~60℃,在500~1100 nm的波长范围内可以观察到明显的表面等离激元共振效应.为了进一步分析该结构的性能,对主要结构参数(抛光面金膜厚度m_(1)、Ta_(2)O_(5)厚度m_(2)、中心空气孔直径d1以及占空比)做了研究分析.仿真结果得到折射率传感下的平均波长灵敏度5700 nm/RIU,最大波长灵敏度13200 nm/RIU,最大振幅灵敏度818.44 RIU^(-1),传感器的折射率分辨率为1.75×10^(-5)RIU.温度传感范围为20~60℃,得到最大波长灵敏度为2.6 nm/℃,最大振幅灵敏度为0.363℃-1,以及传感器的温度分辨率为3.84×10^(-2)℃.该工作对于高灵敏度、实时、分布式、多参量测量SPR传感器的设计和实现具有指导意义.

Design and analysis of high birefringence and nonlinearity with small confinement loss photonic crystal fiber

High birefringence with low confinement loss photonic crystal fiber (PCF) has significant advantages in the field of sensing, dispersion compensation devices, nonlinear applications, and polarization filter. In this report, two different models of PCFs are presented and compared. Both the models contain five air holes rings with combination of circular and elliptical air holes arrangement. Moreover, the elliptical shaped air holes polarization and the third ring air holes rotational angle are varied. To examine different guiding characteristics, finite element method (FEM) with perfectly matched layer (PML) absorbing boundary condition is applied from 1.2 to 1.8 |im wavelength range. High birefringence, low confinement loss, high nonlinearity, and moderate disper-sion values are successfully achieved in both the PCFs models. Numeric analysis shows that model-1 gives higher birefringence (2.75 ×10^-2) and negative dispersion (-540.67 ps/(nm ·km)) at 1.55 |im wavelength. However, model-2 gives more small confinement loss than model-1 at the same wavelength. In addition, the proposed design demonstrates the variation of rotation angle has great impact to enhance guiding properties especially the birefringence.

一种基于光子晶体光纤的高灵敏度Sagnac型温度传感器建模研究

为提高Sagnac型温度传感器的测温范围和灵敏度,提供了一种具有高双折射高温度灵敏度特性的光子晶体光纤设计方法。通过在光纤空气孔内填充温敏液体材料,使光纤具有良好的温敏特性。在COMSOL中建立该光子晶体光纤的电磁场模型并对光纤特性进行分析计算,利用有限元法分析结构参数对双折射和光纤双折射温度灵敏度的影响,并在所确定结构基础上研究了温敏液体的填充方式和填充液体类型对光纤温敏特性的影响。确定了最优的结构和液体填充方式,最优情况下该光纤的双折射温度灵敏度能够达到2.0507×10^(−5)/℃,在1550 nm处可获得5.96×10^(−2)的双折射。将2 mm光子晶体光纤应用于Sagnac型温度传感器中并进行传感性能仿真分析,利用多项式拟合的方法对结果数据进行拟合以分析传感器的温度灵敏度,提高拟合准确性、减小测量误差。结果表明在0~75℃范围内传感器平均灵敏度可达11.28 nm/℃,与现有典型Sagnac型温度传感器相比,本文Sagnac型温度传感器在尽量减小光纤长度的基础上获得了较高的温度灵敏度,并且测温范围更大、准确性更高。因此,该传感器在温度测量领域有一定的应用前景。