Design of Low-Profile Millimeter-Wave Substrate Integrated Waveguide Power Divider/Combiner

A low-profile millimeter-wave substrate integrated waveguide (SIW) power divider/combiner is presented in this paper. The simplified model of this compact SIW power dividing/combining structure has been developed. Analysis based on equivalent circuits gives the design formula for perfect power dividing/combining. In order to verify the validity of the design method, a four-way SIW power divider/combiner circuit operating at Ka band is designed, fabricated and measured. Good agreement between simulated and measured results is found for the proposed passive power divider/combiner. Experiments on the four-way passive divider/combiner back-to-back design demonstrate a minimum overall insertion loss of 1.5 dB at 31.1 GHz, corresponding to a power-combining efficiency of 84%. The measured 10-dB return loss bandwidth is demonstrated to be 2.2 GHz, and its 0.5-dB bandwidth was 2 GHz.     

1 × 4 coupler based on all solid five-core photonic crystal fibers

An improved 1 × 4 coupler based on all solid multi-core photonic crystal fiber is proposed and analyzed. The expressions to calculate the coupling length and the coupling efficiency are deduced based on the coupled-mode equations firstly. Then a full-vector finite element method (FEM) is used to calculate the coupling length and the coupling efficiency. Next, the propagation characteristics and the performances of the coupler are analyzed through using a full vector beam propagation method (BPM). Research shows that the results derived by FEM agree with that by BPM. The coupling length of the coupler is 4.1 mm at λ = 1.55 μm. A maximum coupling efficiency of 24.96% can be obtained. The coupling ratio is more than 22.5% over a wavelength range of 100 nm. The polarization-dependent loss at λ = 1.55 μm is equal to 0.73 dB. Finally, the influences of the micro-variation of structure parameters and the material refractive index on the working performances of the coupler are investigated.     

Linear and nonlinear coupling properties of a novel multicore circular dielectric waveguide

In this work we investigate the linear and nonlinear coupling properties of a novel multicore circular dielectric waveguide. The proposed device consists of a circular central core and many circular sectoral cores at the periphery, while the whole structure can be considered as a nonlinear multicore composite optical coupler. Hybrid guided modes in a circular sectoral dielectric waveguide are derived using circular harmonic expansion for the electromagnetic fields and the Point Matching Method (PMM) for the application of boundary conditions. Several cases are investigated varying some of the parameters of the geometry and the optical frequency in order to produce dispersion diagrams. In advance, the electric and magnetic field distributions for the fundamental guided modes are produced, while linear and nonlinear coupling coefficients as well as the sectoral waveguide mode effective area are derived.     

Matrix-Based Analytical Model of Critical Coupling Length of Titanium In-Diffused Integrated-Optic Directional Coupler on Lithium Niobate Substrate

The critical coupling length Lc is the most important design parameter of an integrated-optic directional coupler, which is the basic building block of a variety of optical integrated circuits. The existing methods of estimating Lc of a Ti in-diffused waveguide directional coupler on LiNbO3 substrate are based on the beam propaga tion method (BPM), which requires huge computing time. A considerably simpler and computationally faster analytical method involving only multiplication of 2 x 2 matrices with no iterations is described in this article. A staircase type step-index profile is generated from the one-dimensional effective index profile in the lateral direction by partitioning the latter into a large number of thin sections of different refractive indices. The overall transfer matrix of the step-index layered structure so obtained may be computed by the progressive multiplication of individual transfer matrices (2 x 2) relating the field components in adjacent layers. Hence the wave amplitude in any layer may be computed as a function of the input wave amplitude for different angles of incidence. This method has been successfully employed to compute the propagation constants for symmetric and asymmetric guided modes in the coupled region of the directional coupler and hence compute the coupling length. The values of Lc computed for a variety of devices agree closely with the published experimental results reported by several research groups. The computer program implementing the model runs reasonably fast in an ordinary PC and is versatile enough to consider arbitrary waveguide dimensions. Ti film thickness, and diffusion parameters for any wavelength of input light and for both transverse electric and transverse magnetic polarizations.     

基于光纤环形腔衰荡光谱的偏振测量

针对传统偏振测量较难同时实现高灵敏度和较好稳定性的问题,提出了一种采用光纤环形腔衰荡光谱技术进行偏振测量的方法,并进行了实验证明.对比分析了掺铒光纤放大器放置在环形腔的内部和外部对脉冲曲线和脉冲数量的影响.在掺铒光纤放大器中使用长度为2m的低增益和低噪声掺铒光纤来减少波形失真并补偿环形腔的内部衰减.利用光纤环形腔衰荡光谱系统对偏振角进行测量,通过记录分析环形腔中光脉冲的衰减时间得到偏振角的变化.结果表明:偏振角和衰减时间在0°~90°的范围内满足良好的线性关系,光纤环形腔衰荡光谱系统的灵敏度和拟合曲线的相关系数分别为4.05μs/°和0.999 6,最大灵敏度误差为0.027 3μs/°.通过10次重复实验,选取六组数据进行拟合得到系统的平均再现性误差为0.030 8,重复性良好,可用于旋光溶液测量,也为光纤径向应力双折射特性和光纤激光器的偏振态测量提供了参考.     

Two dimensional silicon waveguide chirped grating couplers for vertical optical fibers

Shallow etched two dimensional gratings for coupling light between silicon-on-insulator nanophotonic waveguides and vertical optical fibers were designed and experimentally characterized. We show that the large second order back reflection could be suppressed effectively by applying a linear chirp in the grating period for two dimensional grating couplers. The total coupling efficiency from an optical fiber to two orthogonal silicon waveguides is independent of the input polarization. An almost linear relationship between the average effective index of the grating region and the fill factor for 1D grating is obtained and verified. We also show that the average effective index for the two dimensional grating is similar to the one dimensional grating with the same fill factor in the light propagation direction, when the fill factor of the etched holes was larger than 0.5.     

边耦合光腔用于远红外FEL的分析

 模拟了边耦合输出用于FIR FEL 的可实用性，证明这种输出方式适合于远红外FEL。分析且模拟了光腔各种输出参数（如输出功率、腔增益、耦合效率等）随输出镜尺寸及位置的变化规律，找出了最佳的输出镜尺寸及位置。并对谐振腔有漂移管和无漂移管两种情况进行了比较。通过移动或者更换输出镜（输出反射镜），改变输出镜尺寸和位置，可以灵活地选择和调节光腔的Q值。能适应实验不同阶段的需要：例如在实验初期可以提高Q值，增大净增益；而在做饱和实验时可以增大输出，使输出功率最大。     

未知耦合腔体积活塞发声器声压级的检测

本文简要介绍了活塞发声器的工作原理及其声压级的测量原理，着重分析了未知耦合腔体积活塞发声器的有效体积与声压级的测量方法。     

Microwave Assisted Synthesis of 6-Aryl-3-substituted-5H-[1,2,4]-triazolo[4,3-b][1,2,4]triazoles: A Case for a Comparative Study

A simple and fast synthesis of 6-aryl-3-substituted-5H-[1,2,4]-triazolo[4,3-b][1,2,4]triazoles 4 in high yields has been developed by microwave assisted heterocyclization of N-(3-methylthio-5-substituted-4H-1,2,4-triazol-4-yl)benzenecarboximidamides 3 . The effectiveness of the microwave irradiation and conventional heating for the formation of compounds 4 has been investigated.     

耦合型光纤振动传感器实验研究

根据单模光纤耦合器的耦合比对耦合区长度变化敏感的特点,提出了一种耦合型光纤振动传感器,并设计了相应的解调系统对传感器的响应进行光电转换和信号处理.进行了静态和动态测试并给出了传感器在振动和冲击激励下的响应曲线,实验结果和压电传感器的测量结果相吻合.结果表明,耦合型光纤振动传感器不仅满足振动测量的要求,而且具有测量准确度高,制作简单,成本较低等优点.