基于石墨烯的光调制器研究进展

首先介绍了石墨烯的光电特性及光调制机理,在此基础上结合石墨烯在光调制器中的研究及应用,综述了国内外基于石墨烯的光调制器研究进展,重点叙述了条形波导结构、M-Z结构、环形腔结构以及一些其它结构光调制器的工作原理及各器件的特性。     

双控石墨烯超材料太赫兹调制器的双频反射特性（英文）

设计了双控太赫兹超材料调制器,并研究了其在太赫兹频段内两个频率处的反射特性。该调制器由开口环谐振器及其底部的"三明治"结构组成,"三明治"结构从上到下依次为石墨烯层、聚酰亚胺层和金层,其中开口谐振器的开口处填充硅。该结构可以通过电、光两种方式调制,即分别对调制器中的石墨烯施加低电压,对硅施加弱光照。结果显示:反射谱在频率0.806THz、1.869THz出现两个共振反射谷,在满足低激励的条件下,增强两种激励均能改变共振反射谷的反射强度。两个共振处的反射调制方向表现出先反向、后同向的特点,其临界点对应的石墨烯费米能级和硅电导率分别为13.489meV、970.54S/m。文章对同时施加两种激励的情况进行了详细研究,结果表明:同时施加两种激励的调制特性并非单独施加激励的数值叠加,电、光两种调制方式相互独立。在调制过程中,调制器出现的最大调制深度为99.74%。     

硅基环形电-光调制器的理论分析和性能优化

对硅基环形电-光调制器的电学特性和光学特性进行了理论分析.给出环形电-光调制器的调制速率解析表达式.该表达式表明,环形调制器的光学谐振特性对于整个系统调制速率起重要的作用.分析得到调制速度和Q值及波导宽度的关系.并给出了定量的表达式,它可以用于器件特性的优化,同时从理论上指出该器件的理论极限调制速度大于10,GHz.     

硅基Ⅳ族材料外延生长及其发光和探测器件研究进展

硅基光电集成回路是信息时代最具影响力的核心技术之一,由硅基光源、光电探测器、光调制器等模块组成.硅材料是微电子集成电路的基石,然而在光电集成方面却遇到了瓶颈.首先,由于硅是间接带隙材料,其发光效率极低,因此难以应用于硅基高效光源的研制.其次,硅在近红外通讯波段吸收系数很低,因此在近红外光电探测器的应用中具有较大的局限性.然而,研究者发现,通过能带工程将硅与其他Ⅳ族材料相融合不仅可以有效提高直接带高效发光效率,同时能使材料在近红外波段具有较高的吸收系数.因此,以Ⅳ族材料为基础,与硅工艺兼容的硅基光电集成回路引起了研究者的广泛关注.本文综述了课题组在硅基材料外延生长及其发光和探测器件方面的研究进展.介绍了硅基Ⅳ族材料Ge,SiGe/Ge异质结和量子阱材料的外延生长技术,以及硅基GeSn量子点发光材料的制备新方法.基于硅基Ⅳ族异质结构材料,发展调制金属与半导体接触势垒高度新机理,研制了多种结构的光电探测器.设计并制备了与互补金属氧化物半导体(Complementary Metal Oxide Semiconductor,CMOS)结构兼容的横向异质结以及双有源区垂直共振腔型两种结构硅基电致发光器件,有效提升器件的发光性能,并观察到应变锗发光增益现象.     

微波光调制器

自从电光晶体对光的调制现象发现以后,人们已经应用ADP、KDP和CuCl晶体做成了光调制器。到目前,已经发展到应用LiNbO_3、LiTaO_3和电光晶体膜。调制方式也从一般的调制发展到做成微波光调制器。微波光调制器是激光应用中的关键之一。无论宽带光通讯、光多普勒雷达及激光测距(包括七十年代的激光测月),都要用到光     

《中国学术期刊文摘》综述文摘选登

亚微米尺度高速电光调制器研究进展周亮(中国科学院半导体研究所,集成光电子学国家重点实验室,北京100083)基于SOI(silicon on insulator)材料的亚微米尺度电光调制器成为研究Si光电子学的重点。评述了亚微米尺度下SOI脊型光波导实现单模条件、偏振无关、低耦合损耗的技术要求,分析了几种基于不同光学结构和电学结构的电光调制器的原理和特性,讨论了达到高速电光调制的方式。     

激光二级管微波阻抗及正弦调制特性测试的研究

研究了用微波网络分析仪组成的ＬＤ电光特性测试系统。对采用微带线结构的 光调制器和光检测器电路作了详细分析。并运用系统误差修正的理论和方法对国产ＬＤ 的微波特性和调制特性参数进行了测试，结果表明精度和可靠性达到国外八十年代同类 系统水平。     

低噪声、宽谱响应的碳纳米管薄膜-石墨烯复合光探测器

采用高纯半导体碳纳米管薄膜和石墨烯构建复合结构光探测器, 研究其光电响应特性。结果表明, 在光照下, 顶层石墨烯中的光生载流子通过碳纳米管与石墨烯之间薄的非晶硅层, 隧穿至底层的碳纳米管薄膜中, 在非晶硅层两侧分别富集电子和空穴, 形成光致栅压(Photogating), 有效地改变了碳纳米管薄膜晶体管的电流。器件在可见光(633 nm)条件下得到响应度为83 mA/W, 并在近红外波段范围内仍保持好的光响应特性。由于石墨烯具有宽谱光吸收特性, 半导体碳纳米管薄膜晶体管具有小的暗电流, 碳纳米管–石墨烯复合光探测器发挥了两种材料的优势, 为今后高性能宽谱光电探测器的制备奠定了基础。     

衰减全反射电光调制器的实验研究

该文提出并制备了具有棱镜－银膜－聚合物－银膜四层结构的衰减全反射电光调制器，由于选择了新的工作角，驱动电压相对于传统的衰减全反射型电光调制器大大降低，并且调制深度提高，插入损耗很小，材料的配置方便，成本低廉，在此基础上实验研究了它的一些调制特性。     

液晶光学双稳态及自振荡研究

研究了一种扭曲向列相液晶电光调制器的电光特征，讨论了在两种不同偏振配置下液晶对光行为的影响及两种电光特性的区别，实现了液晶调制光学双稳态及多种光逻辑工作状态，发现了一种新的自振荡，观察到振荡的阈值现象和振荡周期对偏压的依赖关系．由于液晶非线性系数大，实验中只需中等强度的连续激光，避免了使用高强度脉冲激光而产生的脉冲间的不确定性。     

A graphene-based broadband optical modulator

Integrated optical modulators with high modulation speed, small footprint and large optical bandwidth are poised to be the enabling devices for on-chip optical interconnects. Semiconductor modulators have therefore been heavily researched over the past few years. However, the device footprint of silicon-based modulators is of the order of millimetres, owing to its weak electro-optical properties. Germanium and compound semiconductors, on the other hand, face the major challenge of integration with existing silicon electronics and photonics platforms. Integrating silicon modulators with high-quality-factor optical resonators increases the modulation strength, but these devices suffer from intrinsic narrow bandwidth and require sophisticated optical design; they also have stringent fabrication requirements and limited temperature tolerances. Finding a complementary metal-oxide-semiconductor (CMOS)-compatible material with adequate modulation speed and strength has therefore become a task of not only scientific interest, but also industrial importance. Here we experimentally demonstrate a broadband, high-speed, waveguide-integrated electroabsorption modulator based on monolayer graphene. By electrically tuning the Fermi level of the graphene sheet, we demonstrate modulation of the guided light at frequencies over 1?GHz, together with a broad operation spectrum that ranges from 1.35 to 1.6?μm under ambient conditions. The high modulation efficiency of graphene results in an active device area of merely 25?μm(2), which is among the smallest to date. This graphene-based optical modulation mechanism, with combined advantages of compact footprint, low operation voltage and ultrafast modulation speed across a broad range of wavelengths, can enable novel architectures for on-chip optical communications.     

A high-speed silicon optical modulator based on a metal-oxide-semiconductor capacitor

Silicon has long been the optimal material for electronics, but it is only relatively recently that it has been considered as a material option for photonics. One of the key limitations for using silicon as a photonic material has been the relatively low speed of silicon optical modulators compared to those fabricated from III-V semiconductor compounds and/or electro-optic materials such as lithium niobate. To date, the fastest silicon-waveguide-based optical modulator that has been demonstrated experimentally has a modulation frequency of only approximately 20 MHz (refs 10, 11), although it has been predicted theoretically that a approximately 1-GHz modulation frequency might be achievable in some device structures. Here we describe an approach based on a metal-oxide-semiconductor (MOS) capacitor structure embedded in a silicon waveguide that can produce high-speed optical phase modulation: we demonstrate an all-silicon optical modulator with a modulation bandwidth exceeding 1 GHz. As this technology is compatible with conventional complementary MOS (CMOS) processing, monolithic integration of the silicon modulator with advanced electronics on a single silicon substrate becomes possible.     

Micrometre-scale silicon electro-optic modulator

Metal interconnections are expected to become the limiting factor for the performance of electronic systems as transistors continue to shrink in size. Replacing them by optical interconnections, at different levels ranging from rack-to-rack down to chip-to-chip and intra-chip interconnections, could provide the low power dissipation, low latencies and high bandwidths that are needed. The implementation of optical interconnections relies on the development of micro-optical devices that are integrated with the microelectronics on chips. Recent demonstrations of silicon low-loss waveguides, light emitters, amplifiers and lasers approach this goal, but a small silicon electro-optic modulator with a size small enough for chip-scale integration has not yet been demonstrated. Here we experimentally demonstrate a high-speed electro-optical modulator in compact silicon structures. The modulator is based on a resonant light-confining structure that enhances the sensitivity of light to small changes in refractive index of the silicon and also enables high-speed operation. The modulator is 12 micrometres in diameter, three orders of magnitude smaller than previously demonstrated. Electro-optic modulators are one of the most critical components in optoelectronic integration, and decreasing their size may enable novel chip architectures.     

基于电吸收调制器的新型40 Gbit/s光学3R重生器

全光3R重生技术（重整形、重定时、重放大）是将来高速大容量全光网中的关键技术.提出了一种结构简单而且性能稳定的40 Gbit/s光学3R重生器,它是基于电吸收调制器的2个波长转换器与基于行波电吸收调制器的光钟恢复器构成的,具有造价低、性能稳定等优点,在未来大容量超高速全光网中具有很大的应用潜力.     

基于行波调制器的光量化器

介绍了一种基于行波调制器的光量化器.调制器的量化工作是建立在Pockels效应原理之上.当极化光通过加有电压的电光晶体时,光的极化方向发生偏转,偏转的角度正比于电压.用多个不同半波电压的行波调制器并联.这些调制器对同一输入射频电压,使用序列光脉冲分别进行量化,并构成二进制多bit位输出的光数字信号.依据这种结构原理,可以制成8-bit,12-bit等高精度量化器.量化速率可达100 GS/s.量化噪声不随bit位增加而增加.给出了4-bitA/D量化器的计算机仿真结果.     

Strong quantum-confined Stark effect in germanium quantum-well structures on silicon

Silicon is the dominant semiconductor for electronics, but there is now a growing need to integrate such components with optoelectronics for telecommunications and computer interconnections. Silicon-based optical modulators have recently been successfully demonstrated; but because the light modulation mechanisms in silicon are relatively weak, long (for example, several millimetres) devices or sophisticated high-quality-factor resonators have been necessary. Thin quantum-well structures made from III-V semiconductors such as GaAs, InP and their alloys exhibit the much stronger quantum-confined Stark effect (QCSE) mechanism, which allows modulator structures with only micrometres of optical path length. Such III-V materials are unfortunately difficult to integrate with silicon electronic devices. Germanium is routinely integrated with silicon in electronics, but previous silicon-germanium structures have also not shown strong modulation effects. Here we report the discovery of the QCSE, at room temperature, in thin germanium quantum-well structures grown on silicon. The QCSE here has strengths comparable to that in III-V materials. Its clarity and strength are particularly surprising because germanium is an indirect gap semiconductor; such semiconductors often display much weaker optical effects than direct gap materials (such as the III-V materials typically used for optoelectronics). This discovery is very promising for small, high-speed, low-power optical output devices fully compatible with silicon electronics manufacture.     

高速率电光调制器偏置电压自动控制技术

采用电光检测的方法和误差分析的方式判断和识别电光调制晶体半波电压的漂移。利用PID控制算法实现高速率电光调制系统偏置电压高精度自动调节。最后对将研究的偏置电压自动控制系统应用于电光调制晶体,进行高速率调制实验。实验结果表明:采用偏置电压自动控制技术,改变了给电光调制晶体加载一个固定偏置电压的传统方式,使电光调制器偏置电压始终位于线性区的中点,以保证不失真调制,克服了电光调制器的半波电压受环境温度等多种因素的影响变化而电光调制晶体的半波电压发生漂移的问题。     

一种使用基于∑Δ分频的频率合成器的GMSK调制器

从调制器的基本结构出发 ,讨论了采用间接调制方法来产生 GMSK信号的原理 ,分析了这种新型调制器的性能 ,给出相应的设计方法 ,并给出相应的仿真结果。     

基于DSP Builder的数字调制器的设计

设计使用DSP Builder实现了基于现场可编程门阵列(Field-Programmable Gates Array,FPGA)的数字调制器。首先,在Simulink中采用DSP Builder的模块建立直接数字频率合成器(Direct Digital Synthesizer,DDS)子系统模型,根据它分别建立四相相移键控(Quaternary Phase Shift Keying,QPSK)和十六进制正交幅度调制(16-Quadrature Amplitude Modulation,16QAM)系统模型;然后使用Signal Compiler工具生成与其对应的HDL设计文件和TCL脚本;最后使用Quartus Ⅱ和ModelSim共同完成功能和时序仿真。仿真结果表明该设计方法正确有效,可广泛应用于数字调制技术的FPGA实现。