水填充太赫兹空芯布拉格光纤温度特性研究

空芯太赫兹(Terahertz,THz)光纤因其损耗低 和易集成功能材料等优点是当前 研究热点。液态水在太赫兹频段具有的独特性质使其在太赫兹辐射、传感和器件等方面具有 多种潜在应用。本文设计一种带有水缺陷层的太赫兹空芯布拉格光纤(hollow core Bragg fiber,HCBF),并采用有限元法分析了其温度特性。结果表明,设计的太赫兹光纤在0.34 THz到0.44 THz频段内存在明显的温度可调的吸收峰,且限制损耗随 着水温的升高而增加。 同时,光纤具有较高的核芯功率比,其值均大于98.6%。本文所研究 的水填充太赫兹光纤在 研究太赫兹与液体相互作用、太赫兹调控器件等领域具有潜在的应用价值。     

表面等离子体慢光波导传输特性分析

表面等离子体可以在亚波长尺度上实现对可见光及红外光的控制处理,对光集成的发展有巨大的推动作用。文中设计了金属—介质—金属结构的表面等离子光波导,并利用时域有限差分法对其色散特性、群速度、场强分布进行分析。结果表明在一定的频率范围内,此结构的光波导可以支持慢光模式,且群速度色散较小,可以有效控制光脉冲的畸变,保持信号的完整性。     

Analysis of dispersion properties in square hollow fiber

A hollow fiber with new cross section was studied by means of a numerical simulator based on the finite-difference time-domain (FDTD) method. Its guiding mechanism was the right angle internal reflection. Results show that light can be confined into the air core due to the right angle guiding mechanism that was implemented with the hollow square glass. Distributions of the transverse electric field intensity as well as dispersion properties of the fundamental mode were given. This fiber can be used in optical communication, gas sensing, enhanced Raman scattering, CO/sub 2/ laser guidance, and particle transport.     

Analysis of dispersion properties in hexagonal hollow fiber

A hollow fiber with new cross section is studied by means of a numerical simulator for modal analysis based on the finite-difference time-domain method (FDTD). Results show that light can be confined into the core area due to six right angles of the hexagonal glass with high index, and the peak intensity is located in the low-index air region. Distribution of the transverse electric-field intensity as well as dispersion properties of the fundamental mode are given.     

Low loss and low dispersion hybrid core photonic crystal fiber for terahertz propagation

In this paper, a hybrid-core circular cladded photonic crystal fiber is designed and analyzed for application in the terahertz frequency range. We introduce a rectangular structure in addition to a conventional hexagonal structure in the core to reduce the material absorption loss. The modal characteristics of the fiber have been investigated using full vector finite element method. Simulated results exhibit an ultra-low effective material loss of 0.035 cm\(^{-1}\) and ultra-flattened dispersion of 0.07 ps/THz/cm. Some other important fiber characteristics suitable for terahertz signal transmission including confinement loss, core power fraction, effective area and single-mode conditions of the fiber have also been investigated. In order to simplify design and facilitate fabrication, only circular shaped air holes have been employed. Due to its promising characteristics, the proposed waveguide may provide efficient transmission of broadband terahertz signals.     

光纤中非线性阻尼对类明孤子传输特性的影响

研究了光纤中非线性阻尼对类明孤子传输特性的影响,导出了类明孤子脉冲参数演化的动力学方程.对于常规单模光纤,光纤非线性阻尼将对类明孤子脉冲的振幅、脉宽、啁啾、频率和相位参数有影响,而对位置参数ξ无影响.     

光纤非线性色散对类明孤子传输特性的影响

应用类明孤子在单模光纤中非线性传输特性的微扰理论,研究了光纤非线性色散对类明孤子传输特性的影响,导出了类明孤子参数演化的动力学方程。结果表明：光纤非线性色散微扰对类明孤子脉冲位置、频率和相位参数有影响,而对类明孤子脉冲振幅、脉宽、啁瞅参数无影响。     

基于太赫兹布拉格光纤的表面生物传感器

空心布拉格光纤在传感领域应用极为广泛。本文提出了一种基于带有缺陷层的太赫 兹(terahertz,THz)空心布拉格光纤的表面生物传感器,并对该传感器在太赫兹频段的细菌种类检测性能进行 分析。在太赫兹布拉格光纤中,高折射率光敏树脂层和低折射率空气层以纤芯为中心周期性 排列,在纤芯内壁沉积分析物引入缺陷模式。本文对提出的传感器性能进行了数值研究。仿 真结果表明,该传感器有很高的纤芯功率比,限制损耗在0.3 THz和0.45 TH z频 段有损耗峰,能得到可识别的特征频率,此特征频率用于细菌种类检测。当频率大于0.7 TH z时,该传感器可实现厚度无关的表面生物传感。本文所提出的基于太赫兹空心布拉格光纤 的 表面生物传感器可用于检测细菌种类,在微生物检测方面有很大的应用潜力。     

Slow-wave propagation on MIS periodic coplanar waveguide

A metal-insulator-semiconductor periodic coplanar waveguide is described. The propagation constants and the characteristic impedances of each section are calculated by the spectral-domain method, and overall propagation characteristics are estimated by the theory of periodic structure. The line should be useful for monolithic microwave integrated circuits.     

Transverse modes of active hollow waveguide resonators

The effect of an active medium on the mode structure of a hollow waveguide resonator is investigated. A coupled-mode approach is employed. The field propagation through the resonator is described by a propagation matrix; thus, the solution is found by solving the generally nonlinear eigenvalue problem of the matrix for complete resonator round-trip. This has been performed numerically using an appropriate iteration procedure. The method was applied to duel-case I resonators. It was found that thermally induced refractive index profiles and, in the case of larger guide cross sections, the gain properties can also alter the mode structure significantly. These alterations influence the power gain coefficient as well as the conditions for single-transverse-mode operation     

Polarizing properties of a high index birefringent waveguide on topof a polished fiber coupler

The polarizing properties of a device made up of a high-index birefringent planar waveguide and a polished-type fiber coupler are analyzed. Approximate analytical formulas are derived for the width and the relative spacing of the TE and TM coupling resonances between the fiber and the waveguide. Experimental results are also shown and a practical in-line fiber polarizer based on this principle is demonstrated     

光纤中皮秒高斯脉冲的传输特性研究

对描述具有初始频率啁啾的皮秒高斯脉冲传输的微分方程组用龙格-库塔算法进行了求解,得到了高斯脉冲各参数随距离演化的数值解并据此画出了高斯脉冲包络的演化。数值结果表明：二阶色散与光纤非线性的比值为0.72时,脉冲的展宽可以被光纤非线性有效地补偿,且脉冲的频率抖动和啁啾也可以得到较好的抑制,但是过强的三阶色散和初始啁啾将导致脉冲能量的迅速衰减和波形的快速畸变。     

掺杂型塑料光子晶体太赫兹波导色散特性研究

文章设计了一种新型的塑料光子晶体太赫兹波导,该波导包层为聚乙烯(含周期性排列的三角格子型空气孔),芯层为有机材料聚四氟乙烯.采用时域有限差分(FDTD)法仿真得到色散特性曲线.研究结果表明,该掺杂型塑料光子晶体太赫兹波导是一种适合太赫兹波传输的光子带隙效应型波导.在太赫兹波段具有良好的传输特性.     

Development of quasi-end-fired waveguide plastic dye laser

A quasi-end-fire (QEF) pumping scheme was proposed and studied as a novel laser-pumping-scheme for a laser-dye-doped plastic waveguide laser with distributed feedback. This pumping scheme resembled longitudinal pumping, but also has the advantage of controllable absorption length of the injected pump beam. A first demonstration of the QEF was performed and the pumping beam controlling was also investigated.     

Polarization properties of a fiber to planar waveguide couplerincorporating a thin metal layer

A fiber to planar waveguide coupling structure incorporating a thin metal layer is described. The resonant wavelengths for the TM polarization were found to be highly sensitive to the refractive index of the superstrate material while those for the TE polarization were unaffected. A theoretical model for the multilayer structure was developed on the basis of a matrix method approach and a preliminary analysis of the resonance shift phenomena for the TM mode shows good agreement with experiment     

光纤中随时间变化的三阶非线性对类明孤子传输特性的影响

从MNLS方程出发,考虑三阶非线性微扰的作用,采用变分法,求得拉格朗日密度函数表达式。在此基础上,推出了类明孤子脉冲参数随传输距离的演化方程组,讨论了三阶非线性微扰对类明孤子传输特性的影响。     

Investigation of the effects of process-induced disorder location on planar photonic crystal waveguide properties

The effects of process-induced disorder location on planar photonic crystal waveguide properties are numerically investigated using three-dimensional finite difference time domain simulation by introducing random fluctuations of the hole radius, size, position, and shape of air-holes of two-dimensional planar photonic crystal slab. Results reveal that bandgap properties are extremely robust with respect to disorder. It is shown that the very first rows of holes play a major role in the amount of disorder-induced optical loss, and that keeping the first two rows of holes unchanged leads to a blue-shift of slow light waveguide properties.     

介质覆盖的金属中空波导的制作及其传输特性

采用液相沉积的方法,在直径为530μm的玻璃管中制备出了用于CO2激光传输的Agl覆盖的Ag中空波导。在对波导中Agl和Ag层的厚度进行控制,并对波导进行有效的冷却后,测出直波导中的损耗为1.56dB/m。     

Simulation of waveguide birefringence by beam propagation method

It is demonstrated that, by modifying the waveguide geometry, the beam-propagation method (BPM) can be extended to determine the mode indexes of both polarizations. Such an approach has been implemented into BPM routines. It can be used to determine the birefringence in waveguide structures. The same approach is also applicable in other waveguide simulation programs based on the scalar field approximation. The operational principle and numerical results for planar waveguides are presented, and the extension of this technique to channel waveguides is discussed.<>