具有负折射的二维光子晶体设计

提出一种具有负折射特性的二维光子晶体设计。对其色散关系的分析表明,该设计对归一化频率为0.5263的TE极化光波具有负折射特性。时域有限差分(FDTD)数值计算模拟结果证明了分析的正确性;并且负折射对光子晶体层数没有依赖关系;很薄的光子晶体就能表现出明显的负折射,且便于实验制作和探测;在一定入射角范围内,光子晶体平板表现出奇异的负折射导引现象。给出了光子晶体模型参数。     

开环光子晶体光纤化学传感器的设计

为了提高低折射率化学物质监测的灵敏度,采用光子晶体光纤设计了一种在开环内镀有金薄膜的表面等离子体共振传感器。利用仿真软件COMSOL Multiphysics 5.6系统地研究了开环半径、内部气孔大小、金属膜层厚度对该传感器灵敏度的影响。最终在2800～4700 nm的工作波段内设计出折射率检测范围为1.26～1.31的低折射率传感器。该传感器平均灵敏度高达22 500 nm/RIU,最高灵敏度达33 000 nm/RIU。在七氟醚、卤代醚、含氟有机物等低折射率物质检测方向具有较好的应用前景。     

基于亚波长光栅的负折射光子晶体成像研究

理论上折射率为?1的平板超透镜可以实现完美成像,但等效折射率为?1的光子晶体结构,不满足介电常数ε=?1和磁导率μ=?1的条件,光子晶体与自由空间阻抗不匹配,某些角度的入射光与光子晶体内布洛赫波不能耦合,致使该空间频率光信息丢失,限制了光子晶体成像分辨率.为了提高成像分辨率,在光子晶体表面设置亚波长光栅结构,利用光栅的...     

光子晶体负折射效应在糖溶液浓度检测中的应用

探讨了光子晶体负折射效应在糖溶液浓度检测中的应用,在软件中使用时域有限差分法对光在光子晶体中的传播进行了模拟实验。模拟显示：糖溶液的浓度变化与输出功率变化接近线性关系,而线性相关程度受介质柱半径常数的影响。进行了多组参数比对与优化,最终获得了线性度最高的输出功率与糖溶液浓度的对应关系。基于这个对应关系,提出了基于光子晶体负折射效应的糖溶液浓度检测方法并设计了相应的糖溶液浓度检测器。实验结果表明：基于光子晶体的糖溶液浓度检测器具有结构简单、测量精度高、响应速度快、易于与激光器件集成且不受外界电磁环境影响等优点。     

基于正四边形晶格的微结构光子晶体光纤的特性分析

设计了基于正四边形晶格空气孔排列的光子晶体光纤,并在此基础上,通过在纤芯附近引入不同的微结构空气孔,运用全矢量有限元差分法,对不同微结构的光子晶体光纤的模式有效折射率、限制损耗、模场有效面积、非线性系数、波导色散系数等特性参数进行了仿真与分析。结果表明:引入不同的微结构,可以减小有效模场面积和增大非线性系数;引入正四边形微结构空气孔时,其限制损耗整体变化幅度较小;引入正八边形微结构空气孔时,其对应的波导色散系数在中波段变化比较平坦,且在波长为1 550nm处波导色散系数接近于零;引入正十二边形微结构空气孔时,其波导色散系数均为负值且变化幅度不大,可以应用于光纤的色散补偿。根据对引入不同微结构的光子晶体光纤的特性研究,为进一步研究光子晶体光纤提供一定的参考。     

光子晶体光子禁带影响因素的综述

光子晶体由于能够产生与半导体能带结构类似的光子禁带,成为了国内外光通信和光学器件方面研究的热点。介绍了光子禁带的产生机理,对光子晶体禁带的影响因素进行分析,发现各个因素对光子禁带的影响具有明显的规律性。     

光子晶体光纤端面研磨损伤的分析

对光子晶体光纤的端面研磨过程进行研究,讨论了光子晶体光纤端面研磨损伤的特点。针对光子晶体光纤的结构特点,应用有限元法建立了数值仿真模型。通过单一磨粒切削孔壁的仿真实验,分析了不同切削深度下裂纹损伤的产生情况以及不同磨粒直径对光纤孔壁结构造成的损伤。最后通过实际研磨实验验证了分析结果。结果表明:有限元法能够很好地模拟光子晶体光纤的端面研磨过程;研磨过程中,相对于非孔洞区域,孔壁边缘更容易出现损伤,呈现出沿圆周分布的崩塌区域;边缘崩塌区域尺寸随磨粒直径的增加而增加。实验用光子晶体光纤孔壁边缘无崩塌的最大切削深度低于普通光纤脆塑转变的临界切削深度,使用0.02μm的砂纸进行抛光可以有效地避免对光子晶体光纤孔壁造成损伤。     

光子晶体光纤传感器的研究进展

简要介绍了光子晶体光纤的基本结构、导光原理和主要特性.依据传感机理将光子晶体光纤传感器分为4类:吸收型光子晶体光纤传感器、荧光光子晶体光纤传感器、干涉型光子晶体光纤传感器、光子晶体光纤光栅传感器,分别对其工作原理、结构、特点和研究进展进行了讨论.     

FDTD方法在光子晶体光纤中的应用

光子晶体光纤是近年来研究的热点,提出时域有限差分法在光子晶体光纤理论分析中应用的具体方法。通过实例计算,得到了光子晶体光纤的有效折射率等传播参量。     

基于光子晶体光纤的轨道角动量模式的产生

为了让光纤中产生轨道角动量(orbital angular momentum,OAM)模式更加集成化,提出了一种利用光子晶体光纤(photonic crystal fiber,PCF)产生轨道角动量模式的方法。通过设计特殊的PCF,使其本征模的奇偶模传输速度不同,在传输一段距离后形成π/2相位差,从而产生OAM模式。该PCF由中心空气孔、二氧化硅环形层和外包层构成,其中外包层由两层圆形空气孔组成,每层圆的数目为2n+2个,对应产生n阶OAM模式。采用有限元法对所设计光纤进行了三维数值仿真分析,成功产生了+2、+3、+4、+5阶OAM模式。该PCF产生OAM模式的方法,满足了未来光纤通信系统集成化、小型化的趋势,在全光纤模分复用系统中有着潜在的应用前景。     

High sensitivity internal refractive index sensor based on a photonic crystal fiber long period grating

A high sensitivity method is reported for the measurement of the internal refractive index using a photonic crystal fiber long period grating. Long period gratings of different lengths were inscribed in photonic crystal fibers, and the air holes of the fiber had varying refractive indices. A side lobe appeared near the resonant dip through the analysis of the characteristics of transmission spectra showing variation in the refractive index. The resonant dip and its side lobe provided varying sensitivities to the internal refractive index values. The sensitivity of the side lobe was as high as 2343?nm/refractive index unit (RIU), which exceeded the value for the resonant dip (2047?nm/RIU) for refractive indices from 1.3333–1.3792. Due to the high resolution of 8.5?×?10^?6 RIU, this method offers promising applications for biological and chemical analysis in which high-precision refractive index measurements are required.     

Simultaneous measurement of refractive index and temperature based on a long period fiber grating inscribed in a photonic crystal fiber with an electric-arc discharge

A novel fiber sensor composed by two single mode fibers and long period fiber grating based on a photonic crystal fiber prepared by periodic discharge heating has been experimentally investigated to measure refractive index and temperature. A Mach-Zehnder interferometer was formed due to the presence of two fusion spliced collapsed regions in the photonic crystal fiber. The resonance dip and interference pattern were differently influenced by the ambient disturbance, so the dual-parameters were simultaneously measured by analyzing the characteristics of transmission spectrum. After the experimental measurements, refractive index and temperature sensitivities of 117.28?nm/RIU and ?86.29?pm/°C were realized. Therefore, the reported sensor with advantages of easy fabrication, simple structure, and small size has the potential for simultaneous refractive index and temperature measurements involving biochemical sensing applications.     

High sensitivity all-fiber Sagnac interferometer temperature sensor using a selective ethanol-filled photonic crystal fiber

An all-fiber Sagnac temperature sensor based on 3?dB tapered coupling and ethanol selective-filled photonic crystal fiber was demonstrated theoretically and experimentally. The ethanol selectivity-filled photonic crystal fiber has noncircular symmetry and thus exhibits birefringence. The ethanol selective-filled photonic crystal fiber, acting as the sensing element, was inserted in a Sagnac loop interferometer to measure temperature. The output spectra of Sagnac interferometer applied different temperatures were measured and analyzed. Experimental results have shown the temperature sensitivity of the Sagnac interferometer is 1.65?nm/°C in the range of 25–33°C.     

高非线性光子晶体光纤中布拉格光栅的制作

采用相位掩模版法实验研究了高非线性掺锗光子晶体光纤中布拉格光栅的制作。实验中采用的光子晶体光纤的非线性系数约为12 W^－1km^－1,模场直径约为2.4 mm。 分析了布拉格光栅的反射率随着曝光脉冲数的变化,随着曝光脉冲数的增加其反射率逐渐达到饱和,继续增加曝光量发射率开始下降。实验验证了可以在高非线性光子晶体中写入布拉格光栅,得到光栅的反射率为44.4%,这对于研究光纤布拉格光栅的非线性效应和应用具有重要意义。讨论了影响布拉格光栅写入效率的因素。     

Determination of refractive index by a U-shaped multimode fiber sensor

The U-shaped multimode fiber structure is proposed to measure the refractive index of liquid. In the previous work, the U-shaped structure by single-mode fiber has been widely investigated. However, the large bending loss restricted its practical applications, especially for the reflection-type fiber probe. To reduce the bending losses, the multimode fiber is used as the bending section of the fiber sensor in this study. The structures with different bending radiuses are fabricated to verify this design. Moreover, to simplify the interrogation method, the differential intensity interrogation method is used by cascading two fiber Bragg gratings after the U-shaped fiber structure. The low bending loss of the proposed structure is helpful to measure the reflected light power by fiber Bragg gratings. The influence of incident light power fluctuation was largely suppressed by this differential method. In addition, the sensitivity is also increased by a factor of 2 compared with the intensity interrogation method using one-cascaded fiber Bragg grating. The experimental results show that the refractive index sensitivities are ?115.09?dB/RIU in the refractive index range of 1.3405–1.3874 and ?260.24?dB/RIU in the refractive index range of 1.3874–1.4223, respectively.     

含特异材料缺陷层一维光子晶体多缺陷现象及其内部场分布

通过数值模拟和理论分析含特异材料缺陷层一维光子晶体中特异材料折射率与缺陷模式的关系,从而发现调节特异材料折射率可以得到不同状态的振荡透射模。同时还分析了保持特异材料折射率不变的情况下其它材料折射率改变对缺陷模式的影响,理论模拟了含特异材料缺陷层一维光子晶体内部场分布,从而可以非常清晰地再现缺陷模式的局域特性。