Slotted waveguide directional coupler characteristics

A moment method (MoM) solution for slotted waveguide directional couplers which is sufficiently accurate for predicting the couplers' characteristics is demonstrated. The slot length in the waveguide directional couplers considered is about four wavelengths and the wall thickness is about 0.27 λ. To simplify the numerical computation, the formulation assumes a uniform field across the slot aperture and utilizes Galerkin's method with the entire domain sinusoidal basis. A self-consistent method taking the finite wall thickness into account avoids an additional matrix equation, as in other MoM formulations. The final solution forms the basis for an efficient computer code applicable to dielectric-loaded slotted waveguide directional couplers. The uniform field assumption restricts the present solution to narrow slots. Numerical results verify, by comparisons with published analytical and experimental data, that this solution is valid for slot lengths as long as 4λ. A detailed discussion of the characteristics of narrow-wall and broad-wall slotted waveguide directional couplers is presented     

Low-loss fibre-coupled waveguide directional coupler modulator

We report a fibre-coupled Ti: LiNbO3 directional coupler modulator with total fibre-device-fibre insertion loss as low as 1.5 dB for ?=1.32 ?m. Low loss has been achieved by using diffusion parameters to give good mode match to the fibre and low propagation loss, an effective SiO2 buffer layer to eliminate electrode loading loss and a directional coupler geometry which minimises the effect of bend loss.     

The Bragg reflection waveguide directional coupler

A directional coupler formed by two Bragg reflection waveguides (BRWs) with a common finite periodic region between them is analyzed. The coupling coefficient is a sensitive function of the index difference in the periodic coupling section. This feature can lead to a novel kind of electrooptic switch. In addition, the BRW directional coupler exhibits dispersion properties characteristic of the periodic bounding media, which can be used to implement a narrowband wavelength filter and a TE polarizer     

0.5THz波导双定向耦合器设计

介绍了0.5 THz波导双定向耦合器的原理分析及仿真设计.采用双排多孔等间距不等孔径的方案,设计了0.325～0.5 THz宽带波导双定向耦合器,并给出了仿真及测试曲线.测试结果显示,0.5 THz波导双定向耦合器在0.325～0.5 THz全波导带宽内耦合度为(7.6±1)dB,方向性大于18 dB,输入端口回波损耗...     

SOI矩形光波导定向耦合器的研究

提出一种利用有效折射率方法分析SOI矩形光波导定向耦合器的理论,并且取得了与精确解非常吻合的结果,最后得出了一些有用的结论,对分析和设计光波导定向耦合器有一定指导意义.     

Modified 1×2 directional coupler waveguide modulator

A novel 1×2 Ti:LiNbO3 modified directional coupler modulator is demonstrated. The 3 dB operating point requires no bias voltage. The device has a lower switching voltage requirement than a conventional directional coupler.     

Broad-band high-silica optical waveguide star coupler withasymmetric directional couplers

A broadband optical waveguide star coupler with asymmetric directional couplers is proposed. A coupling or splitting ratio of the coupler is flattened with respect to wavelength by choosing appropriate values for Δβ and complete power transfer length. The wavelength characteristics of uniform and alternating Δ&thetas;b directional couplers are investigated, and their broadband operation is shown theoretically. To demonstrate the feasibility of the new proposal, 8×8 star couplers composed of such asymmetric directional couplers are fabricated by using high-silica waveguides on a silicon chip. A star coupler composed of asymmetric directional couplers exhibited 2-dB loss variation in the wavelength range of 1.3-1.55 μm, and this value was almost one fourth of that of a star coupler composed of symmetric directional couplers     

A new multiple-tuned six-port Riblet-type directional coupler in rectangular waveguide

Directional couplers are fundamental components for the realization of power splitting and combining networks. A basic component is the four-port coupler realized in a wide range of different electrical and geometrical configurations. Using multiport directional couplers, with six or more ports, compact power splitting and combining networks can be designed. Most of the multiport directional couplers in a rectangular waveguide found in literature use an E-plane branch-line layout. A special configuration of a six-port narrow-wall short-slot directional coupler (Riblet type) is presented here. The coupler has only one central coupling region, following the Riblet concept based on the differences among the propagation constants of the modes through the coupling region. A number of different solutions have been investigated and some examples are presented here. Moreover, a multituning realized by using input resonators permits one to significantly enlarge the bandwidth. A six-port coupler equally splitting on the output ports the power injected at each input port has been designed for a 8.4% working band. The theoretical and measured responses presented here prove the effectiveness of the multituning concept.     

Optical waveguide directional coupler measurements using amicrocomputer-assisted TV camera system

Characterization of optical waveguide directional couplers using a microcomputer-assisted TV camera system is reported. A fluorescent technique is employed to visualize wave propagation in the optical waveguides, which exhibit small scattering. The method is simple and reproducible, and can be used to estimate waveguide losses and evaluate various optical devices such as waveguide lenses and waveguide interferometers on substrates. As an example of its application, parallel and nonparallel dual-chamber directional couplers and parallel triple-channel directional couplers are measured. Power transfer between the coupled channel waveguides is observed clearly, and coupling coefficients of the couplers are obtained nondestructively. The measured performance of the couplers is in good agreement with that predicted by coupled-mode analysis     

光子晶体线缺陷波导中的慢光研究

研究了线缺陷光子晶体波导中的慢光现象。运用平面波展开法对线缺陷光子晶体波导结构进行了模拟计算,分析了填充因子作为敏感结构参量,其变化对色散性质和群速度的影响。发现光子晶体的填充因子决定了光子晶体带隙中导模的传输特性。随着填充因子的增加,光子晶体波导中的群速度先增大再减小。可以证明,通过改变光子晶体的填充因子,群速度可以达到0.01c以下。     

Tunable photonic crystal waveguide coupler with nematic liquid crystals

Photonic crystals (PCs) have great potential in applications for their ability to control lightwave propagation and the possibilities of implementing PC-based optical waveguide into waveguide coupler systems. In this letter, the novel tunable PC waveguide coupler based on nematic liquid crystals is proposed, and its coupling properties are numerically investigated by using the finite-difference time-domain method. The coupling length of PC waveguide couplers with liquid crystals is shorter than the coupling length of coupler without liquid crystals at the same input wavelength. The refractive indexes of liquid crystals can be changed by rotating the directors of liquid crystals. Then, we can control the direction of light propagation in PC waveguide coupler. These results may provide novel application of switching devices in optical circuits.     

Photonic crystal waveguide analysis using interface boundary conditions

Devices based on combinations of photonic bandgap materials are understood intuitively in terms of the dispersion relations of the constituent periodic and locally homogeneous media. Quantitatively, though, photonic crystal-based devices are analyzed using numerical simulations which take no advantage of the a priori understanding of underlying periodic building-block materials. Here we unite the quantitative and qualitative pictures of photonic crystal devices and their design. We describe photonic crystals as effective media and impose boundary conditions between photonic crystals and homogeneous materials. We express optical field profiles as superpositions of plane waves in the homogeneous parts and propagating or decaying Bloch modes in the crystals, connected by transmission, reflection, and diffraction coefficients at the interfaces. We calculate waveguide modes, coupling lengths in directional couplers, and coupling between waveguides and point defects, achieving agreements of approximately 1% in frequencies and around 2% in quality factors. We use the new approach to optimize waveguide properties in a forward-going method, instead of the usual iterative optimizations.     

基于非对称双芯光子晶体光纤的宽带定向耦合器研究

A novel broadband directional coupler based on an asymmetric dual-core photonic crystal fibet(PCF)is proposed.The asymmetry in the fiher is introduced by the enlargement of one air-hole in dual-core PCF.Numerical investigation demonstrate that broadband directional coupling with spectral width as large as 370 nm and polarization-dependent loss and uniformity lower than 0.2 and 0.5 dB,respectively,can be achieved.In addition,the proposed fiber shows large tolerance to the variation of the fiber parameters.In particular,the fiber length allows at least 10%derivation from the proposed fiber length of 7.7 mm.     

一种0.3 THz二维光子晶体定向耦合器的设计

设计了一种基于二维光子晶体的太赫兹定向耦合器,通过在2个平行的横向线缺陷中加入纵向线缺陷的方式,实现了良好的耦合结构,在太赫兹频段实现了较好的功率耦合特性。这种二维光子晶体带定向耦合器结构紧凑,可用于太赫兹系统中信号功率的检测与监控,具有良好的应用价值。     

一种实现超微光子晶体型定向耦合器的方法

在光子晶体定向耦合器中,通过减小两耦合波导之间介电柱的折射率来增大耦合系数,从而获得更短的拍长,形成超微的器件尺寸。耦合器的奇模场随调制折射率的减小变化不敏感,偶模场向更高频率的方向移动。在同一频率范围内,调制折射率减小,导致拍长随频率变化的函数曲线的斜率随频率增加而增大,这一特性可以在波分复用器中用来减小相邻信号频率差,在相同的器件长度下,可获得更多的信道。采用时域有限差分法验证了拍长随调制折射率减小而减小的变化规律。     

基于自成像效应波导耦合的光子晶体分束器

文章采用时域有限差分法和平面波法作为研究工具,在耦合长度L=7α的条件下研究了光在输出端口的透射率和反射率.结果表明,通过引入额外的介质柱改变耦合区电磁场的相位分布,可使3个输出端口的强度达到均分;并且这种结构的分束器具有很高的输出效率,最高可达到99.5%,这些特性使这种器件在波分复用等方面具有很大的潜在运用价值.     

钛扩散铌酸锂波导多电极■β倒相定向耦合器

本文报道了我们研制的四对电极的定向耦合器.利用电极连接的不同方式,分别测试了一对电极、两对电极和四对电极三种工作状态下器件的工作特性.采用四对电极工作时,器件实现了交叉和直通两种工作状态的电调制.     

用电化学腐蚀法制备氧化多孔硅波导定向耦合器

用一种聚合物材料薄膜作为掩膜 ,通过在电化学腐蚀过程中控制腐蚀电流和时间 ,首次制备出了氧化多孔硅波导定向耦合器。实验中用波长为 980nm的激光作为信号光源 ,观测到了样品的耦合光信号。给出了耦合器耦合系数不确定的因素 ,同时也分析了多孔硅波导传输损耗形成的原因。     

一种弱耦合非对称渐变线定向耦合器的快速设计

给出了一种快速设计任意弱耦合非对称渐变线定向耦合器的方法,以线性渐变为基础,通过仿真优化获取最优渐变,摆脱了传统方法中的复杂运算。为改善定向耦合器在频率高端的定向性,在结构上引入了锯齿加载。设计了一个带宽为0.5GHz到20GHz,耦合度为-25dB的定向耦合器,利用三维电磁仿真软件HFSS进行了结果验证。     

Broadband microstrip directional coupler

A nonuniform microstrip directional coupler with sinusoidally modulated coupling function is presented. The ripple and the amplitude response are controlled by the index of modulation m and the periodicity P of the function. For demonstration, a 20 dB ± 6% coupler is constructed on two different substrates and the experiment shows much flatter coupling response than the uniform or exponential line directional couplers.