Optimizing Design for the Traveling Wave Electrodes in Low-Drive High-Speed Electro-Optic Polymer Modulators

Electro-optic (EO) polymer modulators are very promising in the realization of cost-effective and high-performance optical transmissions. In this article, general strategies and specific designs of the traveling wave electrodes in EO polymer modulators were presented to reduce the modulator drive power while maintaining a broadband response. The optimum device parameters and corresponding conditions were estimated using finite element method based on electrode design. In calculating the results, the comprehensive characteristics of polymer modulator with 1.21 V half-wave voltage and 91 GHz bandwidth was demonstrated with electro-optic interaction length is 20 mm, electro-optic coefficient is 55 pm/V, and operation wavelength is 1.319 μm. These results agree with the 0.8 V half-wave voltage and 30 mm electro-optic interaction length reported in Science. In the five designs presented, a hybrid electrode structure combining CPW and microstrip lines were advanced. The characteristics of this structure are like that of microstrip lines with a single-arm electrode on one arm of the waveguide, but it solves the problem of microstrip to coaxial line transition and corona polarization.     

Optimizing Design for the Traveling Wave Electrodes in Low-Drive High-Speed Electro-Optic Polymer Modulators

Electro-optic (EO) polymer modulators are very promising in the realization of cost-effective and high-performance optical transmissions. In this article, general strategies and specific designs of the traveling wave electrodes in EO polymer modulators were presented to reduce the modulator drive power while maintaining a broadband response. The optimum device parameters and corresponding conditions were estimated using finite element method based on electrode design. In calculating the results, the comprehensive characteristics of polymer modulator with 1.21 V half-wave voltage and 91 GHz bandwidth was demonstrated with electro-optic interaction length is 20 mm, electro-optic coefficient is 55 pm/V, and operation wavelength is 1.319 μm. These results agree with the 0.8 V half-wave voltage and 30 mm electro-optic interaction length reported in Science. In the five designs presented, a hybrid electrode structure combining CPW and microstrip lines were advanced. The characteristics of this structure are like that of microstrip lines with a single-arm electrode on one arm of the waveguide, but it solves the problem of microstrip to coaxial line transition and corona polarization.     

超宽带聚合物调制器的优化设计

设计了一种以聚合物作为材料的低损耗、宽带宽的Mach—Zehnder光波导调制器。分析了调制器的脊波导的模式特性,设计了脊波导的结构,并使用BPM软件模拟了脊形波导的光场分布;通过对光场分布的分析,优化了脊形波导的宽度Wg,脊高6,芯层高度H。同时对聚合物调制器的电极进行了优化,包括电极宽度W和电极间距D,使得调制器有较小的导体损耗以及较好的阻抗匹配。并结合了脊波导的结构参数和电极的优化参数,给出了优化结果,它能够使微波的有效折射率与光波的有效折射率达到匹配,从而使带宽达到177GHz,导体损耗为0．2569dB／cm·GHz1／2。     

DESIGN OF A NEW TYPE OF ELECTRO-OPTIC POLYMER WAVEGUIDE MODULATOR WITH ULTRAHIGH BANDWIDTH

In this article, rectangle, trapezoidal and T type microstrip lines embedded into up cladding of the waveguide are designed. By the analysis of the finite element method (FEM), this embedded microstrip line has perfect velocity matching between the electric signal and lightwave carrier and at the same time, conductor loss of the trapezoidal and T type microstrip lines also reduce. Thus the modulator’s bandwidth increases greatly. Calculations show that, comparing with one of non-embedded rectangle microstrip line which is the most familiar configuration of polymer modulator, the optical 3-dB bandwidths of embedded trapezoidal and T type microstrip increase 264% and 339% respectively under the condition of impedance matching.     

一种基于光学偏置的新型Math—Zehnder调制器结构设计

设计了一种基于光学偏置并以有机聚合物PMMA／DRI作为光波导材料的新型Mach-Zehdner调制器。利用有效折射率法（EIM）,分析了脊波导的有效折射率随脊波导结构参数变化情况,包括脊宽训、脊高b和芯层厚度d,以及上下包层厚度。采用微带线单电极调制方式结合脊波导的结构设计,实现了微波和光波的速率匹配。针对优化的结构参数,采用BPM方法进行光场和功率传输的模拟仿真,完成了非等臂Math—Zehnder调制器的结构设计,实现了两臂89．84。的初始相位差,消光比约为27dB。     

Analysis of velocity-matched Ti:LiNbO3 optical intensity modulators with an extended point-matching method

The point-matching method has been extended to analyse a travelling-wave electrode structure for shielded velocity-matched Ti:LiNbO₃ Mach-Zehnder optical modulators. This method provides a simple and fast approach to analysing the coplanar waveguide with buffer layer, cover shield, and electrodes of finite thickness. The calculated characteristic impedances and microwave effective indices agree well with those obtained using the spectral domain technique and the finite-element method. It is found that in the coplanar waveguide without cover shield it is difficult to achieve velocity matching. The coplanar waveguide with cover shield can be used to achieve velocity matching, but the corresponding characteristic impedance is lower than 50. Both velocity matching and impedance matching can be obtained using a narrow centre electrode. The calculated electric field has been used to estimate the modulation efficiency of the device. Velocity matching can be achieved by adjusting the height of the cover shield, but a compromise must be made between high interaction efficiency and low microwave reflection when choosing the buffer layer thickness and the electrode thickness.     

M-Z型极化DANS聚合物电光波导强度调制器研究

研究了Mach-Zehnder型极化聚合物电光波导强度调制器的制备工艺.器件采用DANS (4-dimethylamino-4′nitro-stlibene)聚合物为电光波导材料，由电光波导层、上下介质缓冲层、上下金属电极层构成五层波导结构.对五层光波导各层之间的光学、化学以及微加工工艺的相互兼容性进行了深入研究.采用紫外光漂白方法制备出侧壁光滑的条波导，采用钨丝电晕极化方法对DANS聚合物波导进行有效极化，使其具有电光特性.通过优化器件制备工艺，研制出工作波长为1300 nm的M-Z型电光波导强度调制器原型器件.实验测得器件半波电压约为10 V，调制带宽约为1 GHz.     

Investigation of multilayer microstrip electrode for an asymmetric Mach–Zehnder modulator

In the condition of velocity matching and impedance matching, Mach–Zehnder modulator can obtain large bandwidth and low driving voltage. Based on Wheeler’s transformation of multilayer microstrip line, effective permittivity of microwave has been analyzed. Both the microwave index and characteristic impedance are affected by the thickness and the width of microstrip electrode. In order to achieve velocity matching and impedance matching simultaneously, a compensation layer is placed on the electrode. The optimal thicknesses of the electrode and the compensation layer as well as the width of electrode have been obtained. Based on single-mode condition, an asymmetric Mach–Zehnder modulator (AMZM) has been designed and simulated by effective index method and finite-difference beam propagation method (FD-BPM). The initial phase difference between the two arms of the modulator has been achieved 0.522π in the linear region. Comparing with the typical MZM, AMZM can get a larger value of f _3dB , increased by 67.32%.     

应用HFSS和Designer对电光调制器的协同仿真

应用ANSYS公司的HFSS和Designer对一种内嵌共面波导电极结构的聚合物电光调制器进行了协同仿真,设计出了带宽为56 GHz的聚合物电光调制器.通过对光波有效折射率和微波有效折射率的优化,实现了速度匹配.同时利用协同仿真方法对电极进行了优化设计,实现了阻抗匹配并降低了微波损耗.结果表明应用协同仿真方法可以提高计...     

High-Speed Coplanar Waveguide Based Submount for 40 Gbit/s Electroabsorption Modulator

A high-speed submount has been designed and fabricated for 40 Gb/s electroabsorption (EA) modulators. The submount contains a coplanar waveguide (CPW) for microwave signal feeding and a Ta₂N thin-film resistor for impedance matching. The CPW transmission line is designed to ensure low microwave loss and reflection, and Ti/Cu/Ni/Au metal is adopted for electrode fabrication to guarantee good contact with the Ta₂N thin-film. The typical reflection coefficient of fabricated submount is estimated to be lower than−21 dB up to 40 GHz. As a demonstration, a high-speed EA modulator was chip-level packaged using the high-speed submount, and the measured small-signal modulation bandwidth was over 40 GHz.     

Optical and microwave analysis of mushroom-type waveguides for traveling wave electroabsorption modulators based on asymmetric intra-step-barrier coupled double strained quantum wells by full-vectorial method

The finite difference method is exploited for a full-vectorial analysis of mushroom-type waveguides for traveling wave electroabsorption modulators (TWEAM) based on asymmetric intra-step-barrier coupled double strained quantum wells (AICD-SQW). In this analysis, the discontinuities of the normal components of the electric field across abrupt dielectric interfaces which are known as the limitations of scalar and semivectorial approximation methods are considered. The optical field distributions in mushroom-type TWEAM based on AICD-SQW and conventional ridge-type TWEAM of the same active region for 1.55 μm operation are presented. The important parameters in the high-frequency TWEAM design such as optical effective index which defines optical velocity and transverse mode confinement factor are calculated. Then, the transmission line microwave properties (microwave index, microwave loss, and characteristic impedance) of TWEAMs are obtained. The modulation response of mushroom-type TWEAM is calculated using circuit model by considering interaction between microwave and optical fields in waveguide and compared with conventional ridge-type TWEAM. It is found that increasing the width of p-cladding layer with the same i-layer to reduce the resistance in p-i-n mushroom-type waveguide of TWEAM based on AICD-SQW can improve the microwave propagation loss and thus the high-speed electro-optical response.     

对称推挽型有机聚合物电光波导调制器

提出了在极化有机聚合物民光波导调制器中使用局域极化结构。利用该结构，能够在电光调制器中实现完全对称的推挽操作。由于将集成光学电光调制器中用的平面电有改为使用眄结构的微带电极，并且将槽一结构用于接地电极，使器件性能发生变化。文中地反映光波与微波的相互作用强度的重叠积分进行了详细计算，并对器件性能的改变进行了比较。结果表明由于局域极化结构的使用，将大大提高器件的调制性能。     

Microwave and millimeter-wave losses in conventional optoelectronic devices

In this paper, microwave characteristics of conventional optoelectronic devices, with emphasis on devices with microstrip (MS) and coplanar waveguide (CPW) electrode structures, are obtained. This analysis is essential for any improvement in the structure of the conventional optoelectronic devices so as to obtain a high performance. Microwave loss is one of the important bandwidth limitation factors in microwave and millimeter-wave (mmW) optical devices. Different sources of loss including ohmic, dielectric and radiating loss in MS and CPW of conventional optical devices are analyzed and compared. The results show that the total microwave loss increases with frequency in conventional MS and CPW waveguides. Also, in traveling-wave optoelectronic devices, the bandwidth is limited in the optical part by effects such as the carrier transit time effect and in the microwave part by factors such as length of the devices in active and non-active sections. In addition, validation of the results in the paper is performed with published theoretical and/or measurement results.     

利用波导截止特性测量微波源辐射功率

 对波导的截止特性作了理论分析，并分析了利用该特性进行高功率微波功率测量的可行性及准确性。在远场条件下，利用该特性对工作频率为1.75 GHz的磁绝缘线振荡器进行了微波功率测量。测量结果表明：微波源辐射功率2.3 GW，辐射模式为TM01主模，实测辐射模式方向图与模拟计算结果一致，微波脉宽大于40 ns，未发现明显的功率击穿现象；使用波导截止特性测量微波功率是可行的，有利于防止接收喇叭的功率击穿，测量精度较高。     

Techniques of microwave permeability characterization for thin films

We review the microwave methods to characterize the material properties, including the established and the emerging techniques in material characterization, especially the permeability spectra of the magnetic thin films.Almost all aspects of the microwave techniques for characterizing the permeability of thin films at microwave frequencies, including the new methods developed by our group, are presented.Firstly, the introduction part is presented.Secondly, the coaxial-line with transmission/reflection methods and the pickup coil with electromagnetic induction method are presented.Thirdly, the most widely used shorted microstrip technique is discussed in detail by the equivalent circuit method, transmission line method,and electromagnetic induction method.Fourthly, the coplanar waveguide method and the near-field probe method are also introduced.Finally, the high temperature permeability characterization by using the shorted microstrip line, the near-field microwave probe, and the shorted microstrip line probe are described in detail.This paper may be useful for researchers or engineers who will build up such measurement fixture to make full use of the existing methods or to develop original methods to meet the requirements for ever-rising measurements.     

Structure Design of Polymer Electro-Optic Modulator with Ultra- Broadband

Using finite element method, lots of calculating focusing on polymer electro-optic modulators with ultra-broadband were done, a few structures were analyzed. Coplanar waveguide electrode system was advanced, a few real examples was given.     

Dual-band microwave duplexer based on spiral resonators (SR) and complementary split ring resonators (CSRR)

In this work, a microstrip dual-band microwave duplexer implemented by means of a pair of dual-band branch-line hybrid couplers and a pair of dual-band band-stop filters is presented. The hybrid couplers are implemented by using complementary split ring resonators (CSRRs), etched in the ground plane, while the band-stop filters are made of spiral resonators (SRs) coupled to the host line. The measured duplexer characteristics are good and the device is compact by virtue of the small electrical size of the employed resonant elements. From this paper, it is clear that CSRRs and SRs are useful particles for the design of dual-band microwave systems requiring various microwave components.     

高速光学模数转换器的分析

详细分析了由x切LiNbO3干涉式共面波导行波调制器阵列构成的模数(A/D)转换器，包括其研究进展。采用保角变换方法分析了梯形共面波导电极参数(包括电极厚度、缓冲层厚度与中心电极和接地电极的边沿倾角β1，βg)与转换器的带宽、损耗、特征阻抗和驱动功率的关系。β1=βg=10°，电极厚度为3μm时，4位A/D转换器的工作带宽为7.3GHz，所需驱动功率为6.7W。数值仿真结果表明，采用梯形共面波导调制器阵列设计分辨率适中的高速A/D转换器是可行的。     

Millimeter wave propagation in transmission lines with magnetized semiconductor element

The peculiarities of electromagnetic wave propagation in transmission lines with a gyromagnetic semiconductor element are analysed. Electromagnetic radiation control is shown to be possible when semiconductor element contacts with the waveguide from the outside and constitutes a part of the transmission line itself. The afore-named possibility is demonstrated using rectangular metal and dielectric waveguides as well as a microstrip line.     

Bragg Reflectors and Resonators in Microstrip Technology Based on Electromagnetic Crystal Structures

Recently, new promising two-dimensional (2-D) Photonic Bandgap Structures (PBG), or more properly Electromagnetic Crystal Structures, for microstrip lines have been proposed. In this paper, we analyze these structures in a manner like a Bragg reflector in optical wavelengths. Joining two of such Bragg like reflectors by means of a conventional microstrip transmission line allows one to design Bragg Resonators. The 2-D periodic pattern of the electromagnetic crystal structure is implemented with circles etched in the ground plane of the microstrip line by means of a numerical milling machine. Simulations have been performed by using HP ^TM Momentum and MDS software, and in accordance with the measurements give, for the Electromagnetic Crystal Structures, new promising potential applications both in microwave and millimeter wave integrated circuits, and also in the experimentation of expensive short wavelength (including photonic) devices by using simpler and cheaper microwave down scaling.