High-speed silicon electrooptic Modulator design

An electrically driven Mach-Zehnder waveguide modulator based on high-index contrast silicon split-ridge waveguide technology and electronic carrier injection is proposed. The excellent optical and carrier confinement possible in high-index contrast waveguide devices, together with good thermal heat sinking and forward biased operation, enables high-speed modulation with small signal modulation bandwidths beyond 20 GHz, a V/sub /spl pi// times length figure of merit of V/sub /spl pi//L=0.5 V/spl middot/cm and an insertion loss of about 4 dB. The modulator can be fabricated in a complementary metal-oxide-semiconductor compatible way.     

A Mach-Zehnder-interferometer-based low-loss combiner

Passive optical combiners have an unwanted 3-dB loss. This is avoided with optical switches, but these need control functions to synchronize with the optical signals. A nonlinear Mach-Zehnder interferometer can provide the combiner function without control signals. In the experiment reported here, this combiner was realized with a fiber component. Semiconductor optical amplifiers (SOAs) acted as the nonlinear phase shifting elements. Thus a proof-of-principle for the self-routing combiner is obtained: optical signals on either of the two input ports are guided to one and the same output port without any control mechanism in the interferometer. The nonlinear effect used is self-phase modulation, caused by carrier depletion in the SOAs as they approach saturation. The optical power at which the nonlinear switching occurred was about -2 dBm. The residual combiner loss was only 0.7 dB     

2×2 InP/InGaAsP MMI-MZI型光开关设计与实验

主要研究基于多模干涉耦合器(MMI)的2×2 InP/InGaAsP马赫曾德型(MMI-MZI)光开关.开关的特性采用BPM(光束传输法)进行器件建模、参数分析与性能优化.开关的结构按照传输波导保证单模传输、低偏振敏感要求进行了设计.光开关通过载流子电注入产生的载流子吸收和带填充效应改变移相臂传输光相位.实验测得光开关在控制电压为6.4 V时可实现交叉态到直通态的倒换,开关和关态串扰分别为-20.49 dB、-19.19 dB.这种开关具有结构紧凑、制作容差大和偏振无敏感等优点,它可以很方便地和其它半导体有源器件集成,在未来DWDM系统中有着非常广泛的应用前景.     

低串扰载流子注入型光开关的设计

针对载流子注入马赫-曾德尔干涉型光开关,提出使用输出比可调的3dB耦合器,补偿相移臂上通过载流子注入实现π相位调制所产生的吸收损耗,从而降低光开关的串扰。使用传输矩阵方法计算分析了载流子注入所伴随的吸收损耗对光开关串扰的影响,同时计算了可调3dB耦合器对光开关串扰性能的改进。计算结果表明,可调3dB耦合器的引入可以有效补偿相移臂的吸收损耗,对改善光开关的串扰性能有着明显的作用。     

2×2多模干涉光开关的设计与制作

以多模干涉耦合器为主体,通过载流子注入效应所引起的折射率改变来调整二重像之间的相位差,当折射率下降所引起的相位改变达到π相位时完成开关功能。在AlGaAs/GaAs/AlGaAs外延材料上,利用两步湿法腐蚀工艺,实际制作了2×2光开关并进行了测试。测试结果表明,工作在1.55μm波段,当注入电流达到160mA时,完成了开关功能。     

一种载边比可调单边带全双工光载无线系统

理论分析了一种基于双平行马赫曾德尔调制器(MZM)的2倍频光单边带调制方案,仿真研究了基于该方案的载波重用全双工光载无线(RoF)通信系统性能.合理设置射频驱动信号相移及双平行MZM主调制器偏置电压产生单边带信号,再调整调制指数以实现光载边比ROCS的连续可调谐.讨论了射频信号相移、主调制器偏置电压、双平行MZM消光比...     

Integration of an electrooptic polymer in an integrated opticscircuit on silicon

This paper presents the joining of active nonlinear polymer waveguides with passive silicon nitride waveguides (SiO₂-Si ₃N₄-SiO₂) to form an integrated Mach-Zehnder modulator with a lateral electrode configuration on a silicon substrate. Passive and active waveguides are based on a silicon-nitride-strip guiding structure. In the active waveguide a nonlinear polymer layer is used to obtain an index modulation via the electrooptic effect. Despite the silicon nitride strip based guiding structure, 63% of the energy of the fundamental mode is guided in the nonlinear polymer (provided by Flamel Technology, Venissieux, France). Poling with field strengths up to 75 V/μm applied to the lateral electrodes has been employed to orient the chromophores. A half wave voltage of 35 V has been measured for an electrooptic coefficient of 5.8 pm/V at a wavelength of 1.3 μm. Optical loss measurements have been done on polymer and passive waveguides. The best results have been 1.8 dB/cm for the active and 0.78 dB/cm for the passive waveguides leading to a total loss of 6 dB for a modulator with an interaction length of 2.5 cm. The coupling loss between a laser diode and the passive waveguide structure was measured to be at least 4.6 dB using a microscope objective and piezo-electric displacement elements. Stability tests under atmospheric conditions have shown a decrease of the electrooptic coefficient which might be due to the hygroscopic behavior of the active polymer. The bandwidth of the modulator has been determined to be 4 MHz     

基于石英衬底的16通道二氧化硅可调复用器/解复用器的单片集成

本文是关于可调复用器/解复用器的单片集成,它由一个16通道200 GHZ的二氧化硅阵列波导光栅和一组马赫增德尔干涉型热光可调光衰减器阵列构成。该集成器件是基于石英衬底的,与基于硅衬底的器件相比,省去了沉积下包层的工艺步骤,并且降低了器件功耗。该集成器件的插入损耗是-5 dB,串扰小于-22 dB。在衰减为20 dB的时候每个通道的功耗只有110 mW。     

Monolithic integration of an amplifier and a phase modulatorfabricated in a GRINSCH-SQW structure by placing the junction below thequantum well

We present results of a novel semiconductor optical amplifier device in which an amplifier and a phase modulator are integrated into a fundamental transverse-mode ridge waveguide. By placing the p-n junction below the quantum well (QW) during epitaxial growth and utilizing the effect of the electric field on the depletion width, the phase of the light from an integrated optical amplifier-modulator is varied. For a modulation reverse bias voltage range of 0.4 V, we have demonstrated a 360°/mm phase shift with less than 1.2 dB of amplitude modulation     

基于多频相位调制的光学单边带调制器研究

提出了一种基于多频相位调制技术实现光学单边 带调制信号产生的新型方案。当含有基频和谐波成分的多频调制信号施加到Mach-Zehnder( MZ)电光调制器上时,若驱动信号波 形选取合适,可使调制后的光信号功率集中在边带谱的一个频率成分上,其它频率成分被抑 制, 从而获得光学单边带调制信号的输出。以十频相位调制为例,计算了与之对应的光学单边带 调 制信号的光谱结构,其中信号能量利用率近88%,载波抑制比大于24dB,边频抑制比大于18 d B, 从理论上证明了本文所述方案的可行性。进一步的仿真结果显示,随着驱动信号谐波数的增 加, 载波抑制比、边频抑制比和信号能量利用率均逐渐增大。可见,为了获得优质的光学单边带 调 制信号,应在实际条件允许的情况下使用尽可能多的调制频率。此方案能量利用率相对较高 , 仅用到了一级商用MZ相位调制器,方案结构简单,是一种产生光学单边带调制信号的有效途 径。     

硅基单片集成单边带调制器

基于CMOS兼容的硅基光子集成工艺,设计并实现了一种具有高边带抑制比的硅基单片集成单边带调制器。单边带调制器采用正交混合耦合器实现上下两臂等幅度、90°相位差的射频信号加载,基于硅基双驱动马赫曾德尔调制器的热移相器调控上下两臂光相位差为90°,实现了效果显著的单边带抑制。基于CUMEC公司CSiP180 Al工艺和工艺设计包(PDK)完成芯片制备,采用金丝引线实现了正交混合耦合器的空气桥结构。测试结果显示该硅基单片集成单边带调制器在18~32 GHz频率内边带抑制比均高于12 dB,在21 GHz工作频率时边带抑制比达到了32 dB。该单边带调制器有望应用在光通信和微波光子系统中。     

中红外波段高速硅基电光调制器设计与优化（特邀）

作为中红外波段中最接近O波段和C波段的波段,2 μm波段区域逐渐引起人们的广泛关注。主要对2 μm波段的马赫-增德尔型调制器进行优化设计和仿真,根据2 μm波长下光模场分布的特点,选用具有340 nm厚度顶层硅的SOI衬底,结合实际工艺中240 nm硅刻蚀深度,得到宽度为600 nm以及平板层厚度为100 nm的最优脊波导结构。通过优化掺杂浓度和掺杂区位置获得综合性能最优的调制器器件,在4 V反向偏压下器件光损耗为5.17 dB/cm,调制效率为2.86 V·cm,静态消光比为23.8 dB,3dB EO带宽为27.1 GHz。同时,与220 nm厚度顶层硅器件相比较,器件的综合性能更为优越。研究内容为后续器件实际制作提供了依据,也为后续2 μm波段光收发集成模块所需调制器设计提供了新的方向。     

Integrated optical switches in silicon based on SiGe-waveguides

The realization of switches in silicon base on monomode Ge-indiffused SiGe waveguides is reported. At a wavelength of 1.3 μm a Mach-Zehnder interferometer switch with a modulation depth of -10 dB at a current of 150 mA is obtained. This is the lowest value reported so far for single-mode optical switches in silicon     

一种改进的载波抑制调制光毫米波信号的产生方案

为了克服光纤无线(ROF)系统中色散对光载波抑制(OCS)调制光毫米波信号传输的影响,提出一种改进的OCS调制方案。使用双驱动马赫-曾德尔调制器(MZM),通过调整两路输入射频信号相位、基带信号增益和直流偏置电压将2.5Gbit/s数据信号仅调制到(OCS)信号的一个边带上传输。理论分析表明,与传统OCS调制光毫米波信号产生方案相比,本文方案解决了色度色散引起的码元走离问题,大大增加了传输距离。仿真实验结果表明,经过110km光纤传输后信号的眼图仍然十分清晰,在BER=10-10条件下,信号经过20、40和60km光纤传输后的功率代价分别为0.78、1.7和1.9dB。     

一种12倍频全双工RoF系统

为提高光载无线(RoF)通信系统倍频系数,提出了一种基于集成双平行马赫曾德尔调制器(MZM)和抑制载波光双边带调制的12倍频光生毫米波方案.理论分析了光生毫米波信号产生机理,讨论了相关参数对光生毫米波信号的影响,理论分析与仿真结果基本吻合.在此基础上设计了一种基于该方案的全双工RoF系统,通过调整基站(BS)线偏振器(...     

40 Gbit/s silicon optical modulator for highspeed applications

A high-speed silicon optical modulator based on the free carrier plasma dispersion effect is presented. It is based on carrier depletion of a pn diode embedded inside a silicon-on-insulator waveguide. To achieve high-speed performance, a travelling-wave design is used to allow co-propagation of the electrical and optical signals along the length of the device. The resulting modulator has a 3 dB bandwidth of ~30 GHz and can transmit data up to 40 Gbit/s.     

Phase modulation efficiency and transmission loss of silicon optical phase shifters

This paper focuses on understanding the phase efficiency and optical loss of MOS-capacitor-based silicon waveguide phase shifters. A total of nine designs have been fabricated using poly-silicon and characterized at wavelengths around 1.55 /spl mu/m. Detailed comparison of design parameters shows that scaling down the waveguide dimensions, placing the capacitor gate oxide near the center of the optical mode, and reducing the oxide thickness significantly enhance phase modulation efficiency. Our best design to date demonstrates a /spl pi/-radian phase shift with 0.8-cm device length and 3-V drive. This phase shifter has a transmission loss of 15 dB, the primary source of which is the poly-silicon regions inside the device. An improved material can reduce loss to as little as 4 dB.     

High-Speed Low-Loss Schottky-i-n InP-Based Optical Modulator for RF Photonics

An InP-based high-speed optical modulator is presented. The Schottky-i-n waveguide structure on InP-based material was used to reduce the switching voltage V_pi and the excess loss, while maintaining high-modulation efficiencies. To minimize residual amplitude modulation and to improve power handling capability, the bulk electrooptic effect in InGaAlAs was utilized for phase shifting. As a result, a simple structure InAlAs-InGaAlAs Mach-Zehnder optical modulator with traveling-wave electrodes was fabricated and characterized. This device achieved a switching voltage V_pi of 3.6 V, extinction ratio (>23 dB) and high-speed operation at 1.55-mum wavelength     

A 60-GHz optical frequency shifter using coupled inverted slotlines

A millimeter-wave optical frequency shifter (OFS) using coupled inverted slot lines (ISL's) is integrated on an X-cut LiNbO₃ substrate, Theoretical analysis shows that the use of the coupled ISL's makes it possible to decrease the distance between the arms of a Mach-Zehnder interferometer for optical frequency shifting. The ISL coupling characteristics measured at 60 GHz coincide well with the calculated ones. A 60-GHz frequency shifting of a 1.3-μm optical carrier is experimentally demonstrated using two- and four-branch OFS's. The theoretical analysis and experimental results of the two-branch OFS show that the ratio of the frequency-shifted signal intensity to the optical image intensity is in proportion to the difference between the applied dc-bias voltage and the half-wave voltage. The four-branch OFS consists of two two-branch OFS's excited 180° out of phase, and can suppress the optical image and original carrier simultaneously. The measurements of the four-branch OFS reveal the optical image suppression of over 12 dB and the original carrier suppression of 5 dB below the desired 60-GHz frequency-shifted signal     

An application of a silica-on-terraced-silicon platform to hybridMach-Zehnder interferometric circuits consisting of silica-waveguidesand LiNbO3 phase-shifters

By using a silica-on-terraced-silicon platform (STS-platform) for optical hybrid integration, we fabricated a hybrid Mach-Zehnder interferometric circuit consisting of silica-waveguide directional couplers and a LiNbO₃ phase-shifter array. The circuit functioned as an optical switch with an insertion loss of 6.0 dB including input and output fiber coupling loss and an extinction ratio of better than 20 dB. The STS-platform was thus confirmed to incorporate both a high-performance planar lightwave circuit and a silicon optical bench