基于光子晶体光纤的局部放电检测

局部放电检测对于保障高压电力系统的安全运行至关重要。本文提出了一种针对高压设备局部放电检测的表面等离子体共振D型光子晶体光纤传感器,该方案采用一种光致变色凝胶作为敏感单元,用于感知局部放电所产生的紫外线辐射。该凝胶的折射率会随辐射强度的变化而变化,从而影响光纤纤芯和表面等离激元模式之间的耦合共振波长。通过全矢量有限元法对传感器的性能进行了理论和仿真分析,并对传感器的几何参数进行了研究,以优化传感器的灵敏度,最后进行了实验验证。结果表明所设计传感器的灵敏度值可达24nm/mW·cm-2。该传感器结构简单、成本低廉,为光纤局部放电传感的研究提供了参考。     

Tunable polarisation-maintaining filter based on liquid crystal photonic bandgap fibre

A tunable and polarisation-maintaining all-in-fibre filter based on a liquid crystal photonic bandgap fibre is demonstrated. Its polarisation extinction ratio reaches 14 dB at 1550 nm wavelength. Its spectral tunability range spans over 250 nm in the temperature range 30?708C. The measured transmission spectrum is compared with that obtained through finite element simulations.     

光子晶体光纤研究

光子晶体光纤以其灵活的结构设计和高非线性、平坦色散、高双折射等独特光学特性吸引了越来越多的关注.简单介绍了光子晶体光纤的分类,导光机理,详细讨论了其相关光学特性,最后介绍了光子晶体光纤的研究进展.     

双矩形纤芯光子晶体光纤偏振分束器

基于双折射效应设计了一种新颖的纤芯为椭圆空气孔,包层为圆形空气孔的矩形双芯光子晶体光纤偏振分束器。用半矢量光束传播法(BPM)数值模拟了基模情形下该偏振分束器的性能,结果表明:在工作波长为1.55μm,光纤长度为1659μm时,两个纤芯在X、Y方向偏振光的隔离度分别达到了-41.3 dB和-39.1 dB,隔离度小于-10 dB的带宽超过了80 nm,达到了良好的偏振分束性能。同时,模拟了实际加工误差对所设计的偏振分束器的影响,得出在1.55μm的工作波长下,误差达到±7%时,隔离度仍能小于-10 dB,具有较高的实际应用价值。     

矩形晶格结构双芯光子晶体光纤偏振分束器的研究

椭圆形空气孔光子晶体光纤可以产生较高的双折射,使得不同偏振方向的光有不同的耦合长度.将光纤的双折射现象应用于双芯光纤中,可以实现偏振状态的分离.应用平面波扩展法分析了椭圆形空气孔、矩形晶格结构的双芯光子晶体光纤中结构参量对光束不同偏振方向的耦合长度的影响,设计了一种基于椭圆形空气孔、矩形晶格结构的双芯光子晶体光纤偏振分束器.应用全矢量光束传播法分析了这种光纤偏振分束器的性能.结果表明,在1.55 μm工作波长上,长度为1.055 mm的光纤即能实现偏振状态的隔离,隔离度达到-16.9 dB,隔离度＜-16 dB的带宽可达到270 nm.     

Tunable photonic crystal coupled-cavity laser

We report the development of a tunable photonic crystal coupled-cavity laser diode based on InP. The laser consists of two photonic crystal channel waveguides that are coupled through a photonic crystal mirror segment in /spl Gamma/-M direction. The cavity lengths define the respective mode spacings in the cavities. The tuning characteristics of the device are compared with results obtained from a transfer matrix model. Quasi-continuous tuning is achieved in a 29.6-nm window with 36 wavelength division multiplexing channels spaced 0.8 nm apart (ITU grid). The simplicity of fabrication and promising output characteristics should make this tunable laser design an interesting source for monolithic integration into highly integrated photonic circuits.     

Tunable Gaussian filter based on tapered liquid crystal photonic bandgap fibre

A tunable Gaussian filter based on a tapered liquid crystal photonic bandgap fibre is presented. The filter is centred at lambda=1062 nm and has a 3 dB bandwidth of 150 nm. Tunability is achieved by exploiting the thermo-optic effect of the liquid crystals. A shift of 110 nm at the central wavelength is observed by increasing the temperature from 30 to 80degC     

Tunable edge-emitting microlaser on photonic crystal slab

A tunable edge-emitting microlaser is realised by a chirped line-defect photonic crystal waveguide. A tunable range of 57 nm is obtained experimentally.     

基于保偏光子晶体光纤的高灵敏度曲率传感器

为了能高精度测量小曲率,采用单模-鼓包-保偏光子晶体光纤-多模-单模光纤组成的结构,其中多模光纤和单模光纤之间错位熔接。通过理论分析和实验验证得到在0.04582m-1~0.054776m-1及0.054776m-1~0.06929m-1曲率范围内,谐振波长漂移与曲率变化之间分别存在着线性关系。结果表明,该曲率传感器灵敏度值分别为93.95nm/m-1和30.89nm/m-1,可以应用于健康监测等需要测量小曲率的场合。     

高双折射双芯光子晶体光纤偏振分束器

设计了一种基于双折射效应的新型矩形纤芯光子晶体光纤偏振分束器,通过在矩形晶格结构的光子晶体光纤的每个纤芯中引入一对椭圆来增加结构的双折射。应用全矢量有限元法（FEM）分析了双芯光子晶体光纤中结构参数对双折射和耦合长度特性的影响,数值模拟了该偏振分束器的性能。结果表明:增大椭圆率可以在增大结构的双折射的同时减小耦合长度,并且该分束器在工作波长为1.55 m、传输长度为282 m 的光纤中能够实现偏振状态的隔离,消光比达到最小值-45.42 dB,并且在1.507~1.596 m、带宽为89 nm 的范围内消光比小于-10 dB。     

A novel polarization splitter based on three-core photonic crystal fibers

A novel polarization splitter based on photonic crystal fibers(PCFs) with three cores of high birefringence is proposed.The 45o linearly polarized light is launched into a core.After a coupling length(about 1500 μm),the xand y-polarized light beams are separated into different cores.When the light is launched into another core,the xand y-polarized light from different cores can be obtained and the degree of separation can be also adjusted.The polarization splitter is highly flexible and adjustable.The lengt...     

一维光子晶体波长可调谐滤波器

介绍了一种将液晶作为缺陷引入到一维光子晶体结构中,实现波长可调谐的滤波器.通过对光子晶体的滤波特性的分析清晰地说明这种光可调谐滤波器的原理和可行性.同时选用手征近晶型液晶,利用电压对这种液晶折射率的调制快于向列液晶的特性,得到符合现在光通信网要求的体积小、阻带区对透光抑制力强、损耗低和开关速度快的可调滤波器.最后,对滤波结构中的重要参数进行了探讨.     

Large-solid-core square-lattice photonic crystal fibers

A large-solid-core fiber design comprised by omitting nine air-holes at the center of square-lattice photonic crystal is investigated for the constant air-hole diameter and for the constant pitch length of air-holes. The fiber characteristics are calculated for both structures, and the results are compared. In the calculations, the plane-wave expansion method is used for effective indices, and we utilized the step-index fiber and Gaussian mode profile approximations for obtaining the effective V-number and the effective mode area respectively.     

Single-polarization single-mode photonic crystal fibers

A new structure of single-polarization single-mode (SPSM) photonic crystal fiber (PCF) is proposed and analyzed by using a full-vector finite element method with anisotropic perfectly matched layers. From the numerical results it is confirmed that the proposed fiber is low-loss SPSM-PCF within the wavelengths ranging from 1.48 to 1.6 /spl mu/m, where only the slow-axis mode exists and the confinement loss is less than 0.1 dB/km.     

基于光子晶体光纤长周期光栅的传感器研究

详细研究了光子晶体光纤长周期光栅(LPG-PCF)的应力和温度特性,利用成功制作的温度不敏感PCF-LPG,实现了两种结构简单光纤传感器.在温度不敏感应力传感器中,PCF-LPG作为温度不敏感的应力传感头,当以波长为1553nm的分布反馈(DFB)激光器为入射光源、用分辨率为0.001dB的光功率计测量时,PCF-LP...     

基于液体选择填充光子晶体光纤的波分解复用器研究

设计了一种基于液体选择填充三芯光子晶体光纤的1.31/1.55um波分解复用器。中间为缺失一个空气孔的普通二氧化硅纤芯,左右两纤芯填充了不同折射率的液体材料。根据光纤的消逝场耦合的模式理论,不对称相邻波导存在波长相关耦合。不同填充折射率的两纤芯与中间纤芯分别耦合,构成两个不同响应波长的光滤波器。通过选择合适光纤长度,可实现不同波长光的分离。采用全矢量有限元法分析了光纤的传输特性,讨论了填充不同折射率液体时波导间的模式耦合,得到了其匹配波长与耦合长度。基于光束传播法仿真发现,长度为4.88 mm的光纤能实现1.31/1.55 um波长光的解复用。     

基于光子晶体平板传导共振模的低功率光开关

利用严格耦合波算法计算了二维光子晶体平板结构随角度变化透过谱和波长变化透过谱,研究了透过谱上传导共振峰与二维光子晶体平板能带结构的关系。利用共振传导模的低透过和高Q值的特点,设计了基于磷化铟材料的工作在1550nm波长附近的角度分辨和波长分辨的光子晶体光开关。理论模拟结果表明,该结构透过谱上传导共振峰品质因子可达105,非线性折射率变化为10-4即可实现开关对比度接近100%。当信号光或泵浦光分别与光子晶体平板传导共振模耦合时,由于共振耦合使得泵浦光场增强,需要泵浦能量仅为184fJ,为目前所知能量最低的光开关。     

Tunable GaInNAs lasers with photonic crystal mirrors

We present results of tunable GaInNAs lasers with photonic crystal (PhQ mirrors, fabricated from GaAs-AlGaAs layers with a double GaInNAs quantum well emitting at IR wavelength. The devices are realized as ridge waveguide lasers with two coupled segments and a total length between 240 and 580 pm. PhC blocks with different thicknesses are used for the back and front mirror as well as for the intermediate reflector between the two segments. The lasers have threshold currents around 20 mA and output powers up to 6 mW. Tuning of the laser emission over 30 nm is achieved by a variation of the currents injected into the two segments.     

Proposal for sum-frequency generation based on modal phase-matching in photonic crystal fibers

In this paper, we report on a feasible phase matching between three low-order modes guided in an appropriately designed photonic crystal fiber (PCF). The phase matching condition for sum-frequency generation (SFG) can be realized over a large wavelength range by modifying the air holes size and the lattice pitch. This can be achieved in the proposed photonic crystal fiber because the sum-frequency wave propagating in a LP₀₂ mode leaks more into the low refractive index cladding than does the fundamental wave. By “feeling the cladding”, the LP₀₂ mode compensates for the increased refractive index of the silica at the sum-frequency wavelength. The numerical results show that the SFG in the proposed nonlinear PCF can be tunable, and the pump and sum-frequency waves are well-confined in the fiber core region.