1550nm低损耗单模全固态光子带隙光纤研究

全固态光子带隙光纤由于其独特的带隙和色散特性以及易于和传统光纤熔接的优势,引起了国内外研究人员的广泛关注.本文采用等离子体化学气相沉积工艺结合堆叠拉制法制备了全固态光子带隙光纤,并运用频域有限差分法模拟了其损耗和色散特性.该光纤1550 nm处有较低损耗且单模传输,计算得到1550 nm处的有效模场面积和色散分别为191.81μm2和16.418 ps/(km·nm),在测试范围1500—1650 nm内损耗小于0.15 dB/m.结合实验结果,对光纤参数做了进一步模拟优化.     

Low-loss all-solid photonic bandgap fiber

We report the fabrication and characterization of a new type all-solid photonic bandgap fiber. By introducing an index depressed layer around the high-index rod in the unit cell of photonic crystal cladding, transmission loss as low as 2 dB/km within the first bandgap is realized for the all-solid photonic bandgap fiber with a bandwidth of over 700 nm. The bend loss experiment shows that the photonic bandgap fiber is much less bend sensitive than single-mode fiber.     

Analysis of microstructure optical fibers by radial scattering decomposition

Radial scattering decomposition, a tool for the modeling and design of microstructure optical fiber, including photonic bandgap fiber, is described. Building on the multipole approach, the method decomposes a fiber structure into radial shells, allowing the confinement of light to be analyzed layer by layer. This approach lends new understanding and suggests a number of new approaches to bandgap fiber design.     

Silica-air photonic crystal fiber design that permits waveguiding by a true photonic bandgap effect

A theoretical investigation of a novel type of optical fiber is presented. The operation of the fiber relies entirely on wave guidance through the photonic bandgap effect and not on total internal reflection, thereby distinguishing that fiber from all other known fibers, including recently studied photonic crystal fibers. The novel fiber has a central low-index core region and a cladding consisting of a silica background material with air holes situated within a honeycomb lattice structure. We show the existence of photonic bandgaps for the silica-air cladding structure and demonstrate how light can be guided at the central low-index core region for a well-defined frequency that falls inside the photonic bandgap region of the cladding structure.     

Electrically tunable Sagnac filter based on a photonic bandgap fiber with liquid crystal infused

We demonstrate an electrically tunable Sagnac filter based on a photonic bandgap fiber that is realized by infusing liquid crystal into a solid-core air-hole photonic crystal fiber. The filter enables an electrical tuning with a range of about 26 nm for one single interference minimum in the transmission bandgap from 1330 to 1650 nm wavelength. The tuning efficiency is averaged to 0.53 nm/V.     

随机光纤激光器中光纤与随机介质匹配问题的研究

降低阈值是随机激光实用化的前提, 随机光纤激光器是将随机增益介质填充到空芯光子晶体光纤中利 用其光子禁带来降低阈值的一种随机激光器. 理论分析表明: 在光子晶体光纤光子禁带的约束下, 随机光纤激光器中的大部分能量被集中在芯区传播, 这使局域在芯区的光与随机介质相互作用得到增强, 激发效率得以提高. 然而, 光纤填充介质后, 纤芯等效折射率发生了改变, 光子带隙也会随之移动, 因此当选用带隙光纤来降低阈值时, 只考虑光纤本身的带隙是不够的, 应考虑到介质的增益频率和填充后的光子带隙之间的匹配问题, 合理选择光纤或介质的材料, 如果匹配得当, 光子禁带对激光的调控能力会更强, 激光阈值有望得到更大程度的降低. 关键词： 随机激光 光子晶体光纤 光子禁带 阈值     

Photonic bandgap fiber with a silica core and multilayer dielectric cladding

A new technique for fabricating a photonic bandgap fiber is proposed. A multilayer Si--SiO2 film is deposited upon a silica glass fiber, and a clear bandgap is observed in the loss spectrum. The properties of the bandgap are easily controlled by adjustment of the thickness and the refractive index of the multilayer film.     

Hollow-core photonic bandgap fibers based on a square lattice cladding

We propose a novel air-guiding photonic bandgap fiber based on a square lattice cladding. The fiber presents a 20% wider bandgap than is achievable with a conventional triangular-lattice-based cladding and with the choice of a nine-cell core can be effectively single moded at all wavelengths within the bandgap.     

Investigation of all-solid photonic bandgap fiber with low losses in low-order bandgaps

We report synoptically an investigation of design, fabrication and characterization of a new all-solid photonic bandgap fiber. By introducing an index depressed layer around a high index core in every unit cell of photonic crystal cladding, a novel all-solid bandgap fiber is predicted to obtain low confinement and bend losses within low-order bandgaps. After optimizing the structure parameters, we fabricate a batch of rods used for cladding cells, select a pure-silica rod for core cell and an inner-hexagonal jacket tube. We demonstrate an all-solid bandgap fiber with the transmission loss as low as 2 dB/km at 1,310 nm and a bandwidth of over 700 nm within the first bandgap. The guiding properties are also measured, respectively, such as transmission spectrum, attenuation spectrum, bend loss, mode field intensity profile, and chromatic dispersion.     

Fabrication of all-solid photonic bandgap fiber coupler

We report the fabrication of a tunable all-solid photonic bandgap fiber coupler based on the side-polishing technique. This device is believed to be the first demonstration of a photonic bandgap fiber coupler to eliminate the contamination of the open air holes. By adjusting the length of the interaction section, the tunable coupling ratio as much as 92.5% at 1550 nm is achieved. The investigation of the spectrum properties shows that the coupler has excellent tunability properties, for which the coupling ratio can be smoothly and continuously controlled.     

空芯光子带隙光纤纤芯-包层交界面的设计

利用平面波展开法计算了圆六边形空气孔按三角形排列的光子晶体带隙,基于带隙图设计了移去7根玻璃毛细管形成纤芯、传输波长λ=1.55 μm的空芯光子带隙光纤的结构参量.随后利用全矢量有限元法计算了所设计的在纤芯-包层交界面处引入石英环的光纤,给出了在不同半径情况下沿z轴方向的光强分布、光强等高线分布图和损耗随引入石英环相对厚度的变化曲线.得出了光纤消除表面模、减小损耗的纤芯外半径取值范围为1.55Λ～1.7Λ,石英环的相对厚度取值范围为1.3～1.5或3.4～3.8.通过分析发现石英环的引入既可以抑制表面模也可以激发表面模,抑制还是激发有赖于纤芯外半径和石英环厚度的选择.     

基于高折射率断环结构的全固光子带隙光纤的设计

设计了基于断环结构的全固光子带隙光纤,其背景材料为熔石英而断环结构由若干掺杂的高折射率介质柱构成.基于平面波展开法计算得到的态密度图和Bloch模场分布表明,该种光纤中的一个高阶带隙可以得到调节并被极大展宽,带隙调节的基本原理是断环可以同时控制包层介质柱的线偏振模式的角向和径向模式阶数.研究表明,断环中的介质柱数目决定了受影响最小的一组线偏振模式的最高角向阶数,而带隙宽度受介质柱尺寸影响很大.这一宽的高阶带隙可以用来设计带隙中心分别在800和1550 nm、带宽分别为488和944 nm的全固光子带隙光纤 关键词： 全固光子带隙光纤 光子带隙 光纤设计 平面波展开法     

All-solid photonic bandgap fiber

We describe the design and fabrication of a photonic bandgap fiber formed with two different glasses. As in a hollow-core fiber, light is guided in a low-index core region because of the antiresonances of the high-index strands in the fiber cladding. The structure described represents an ideal bandgap fiber that exhibits no interface modes and guides over the full width of multiple bandgaps.     

用于液压传感的双芯光子晶体光纤

采用全矢量有限元方法进行光纤设计优化,得到横截面上失去两层空气洞的双芯光子晶体光纤,可用于液压传感.优化的双芯光子晶体光纤的模场半径和数值孔径与单模光纤基本一致,在优化的双芯光子晶体光纤和单模光纤之间有一个相对较低的熔接损耗.计算结果表明由模场半径和数值孔径导致的不匹配造成的总共损耗可低至0.026 dB,低于传统光子晶体光纤和单模光纤0.1 dB的直接熔接损耗.对基于20 cm双芯光子晶体光纤的液压传感器的性能进行研究,结果表明在0～500 MPa量程内的灵敏度为-1.6 pm/MPa.     

PBG光子晶体光纤的色散特性研究

光子晶体光纤(PCF)是一种具有特殊包层结构的光纤,它是利用光子禁带效应(PBG)来导光的。利用时域有限差分法(FDTD)来分析光波在PCF中传输的色散特性,结果表明,PBG光子晶体光纤的色散值和色散斜率比常规的通信光纤要小。     

Detection H2S mixed with natural gas using hollow-core photonic bandgap fiber

An optical fiber gas sensor using hollow-core photonic bandgap fiber as a gas cell is proposed to detect H₂S mixed with natural gas. This sensor is advantageous for eliminating instability of light source, impact of thermal zero drift, and zero shift of photoelectric device. The gas sensing probe of configuration is using two shorter pieces of hollow-core photonic bandgap fiber (HC-PBF) with the same overall length instead of one long piece of HC-PBF to improve the system response. The experimental dates indicate that a minimum detectivity of 10 ppm for the system configuration was estimated.     

Nonlinear interaction between two different photonic bandgaps of a hybrid photonic crystal fiber

Nonlinear interaction between spectral components in two different photonic bandgaps is experimentally demonstrated by launching femtosecond pulses near a zero-dispersion wavelength of a hybrid photonic crystal fiber, which guides by a combination of total internal reflection and bandgap effects. It is demonstrated that the initial pulse becomes spectrally broadened, and narrowband resonant radiation is generated in a different bandgap from the one responsible for guiding at the pump wavelength. The spectral intensity of the resonant radiation peaks at 2.7 dB below that of the broadened pulse in the pump-guiding bandgap.     

单模低损耗光子晶体光纤的设计及特性分析

设计了几种特殊结构的带隙光子晶体光纤,采用平面波展开法和频域有限差分方法研究了基于不同结构光子晶体光纤的带、模式、色散和色散斜率。由平面波展开法和频域有限差分方法求解麦克斯韦方程组导出本征值方程,可以得到带隙光子晶体光纤中可能存在的不同模式的传播常数、电场分布、本征频率和磁场分布。分别给出了第二圈填充率取三种不同值时带、模式、色散和色散斜率的变化。结果表明,当第二圈填充率改变时其特性有明显的变化。随着填充率从0．75减小到0．45,其二阶模分裂成两个类LP01模,可降低损耗。计算结果对单模和低损耗的光子晶体光纤的设计有参考价值。     

Pulse shortening and quality improvement based on spectral filtering in a stretched-pulse mode-locked fiber laser with large third-order dispersion

We demonstrate a passively mode-locked ring fiber laser operating in the stretched-pulse regime. The ring cavity model is constructed with standard single-mode fiber and dispersion delay line for dispersion management. Here, all-solid Yb-doped photonic bandgap fiber is used as the dispersion delay line and provides laser gain simultaneously. As the all-solid Yb-doped photonic bandgap fiber has large third-order dispersion, it is necessary to study its impact on the stretched-pulse operation. The presence of the third-order dispersion reduces pulse quality because of the relatively small group velocity dispersion. To improve the pulse quality, a spectral filter is employed in the model. The simulation results show that spectral filtering could improve the pulse quality and shorten the pulse duration. Meanwhile, the optimum filter bandwidth is studied.     

Rewritable self-assembled long-period gratings in photonic bandgap fibers using microparticles

We report the demonstration of rewritable self-assembled long-period gratings in air-core photonic bandgap fibers. The long-period gratings are written by filling the air-core region of the fiber with a solution containing polystyrene microspheres. The microspheres are self-assembled into a periodic structure as the liquid inside the fiber evaporates, forming the long-period grating. The formed grating can then be easily erased for rewriting purposes by connecting the end of the fiber to a microfluidic pump through a microfluidic channel and washing out the microparticles with an appropriate liquid. The same microfluidic system can also be used to fine control the writing process of the gratings. This technique creates possibilities for writing various different filtering functions in air-core photonic bandgap fibers by varying the composition and/or the shape of the used microparticles. The presented technique is potentially applicable to solid-core photonic crystal fibers as well.