硅衬底上锗硅合金光波导的研制

报道锗硅合金在λ＝１．３μｍ的脊形单模光波导的设计，工艺及测量结果。这种光波导的传播损耗已达０．７ｄＢ／ｃｍ。脊形的高４－８μｍ，宽８－１２μｍ，均和单模光纤芯径相当，此外，其数值孔径在光波导的输入，输出端均能和单模光纤匹配，它已满足硅光集成对光波导的要求。文中最后报道了用这种锗硅合金光波导试制Ｙ分支器，并观察到二支分路输出的单模光斑。     

硅-有机物材料混合电光调制器的优化设计

设计了一种基于绝缘上层硅的硅-有机物材料混合马赫-曾德干涉型高速电光调制器.利用光束传播法对顶层硅为220nm的绝缘上层硅基片上的3dB分束器/合束器的结构参数进行模拟,优化后附加损耗仅为0.106dB.为提高模式转换效率,在条形波导和slot波导之间设计了模式转换器,光耦合效率高达98.8%,实现了光模式高效转化.利用时域有限差分法模拟了slot波导平板区掺杂浓度对波导内光学损耗的影响,在几乎不产生光学损耗的情况下,得到平板区轻掺杂浓度为71017/cm3,调制器设计总损耗为0.493dB.利用薄膜模式匹配法对slot波导结构进行仿真分析,考虑slot区等效电容及平板区等效电阻对带宽的影响,优化后得到slot波导结构的限制因子为0.199.采用slot波导与强非线性有机材料LXM1结合的绝缘上层硅平台实现了强普克尔效应,得到电光调制器半波电压长度积为1.544V·mm,电学响应3dB带宽为137GHz.     

离散谱折射率法分析深刻蚀、单模GaAs/GaAlAs脊形光波导

本文采用离散谱折射率法对深蚀刻、GaAs/GaAlAs多层脊形光波导模式特性进行了具体分析和设计,获得了较大截面、低损耗的单模脊形光波导.利用这种横向具有最大折射率差的深蚀刻脊形光波导不但可以提高多模干涉(MMI)型器件的性能,而且在设计和制作弯曲波导、分支结构时,具有结构紧凑、易于集成等优点.     

行波电极硅-有机复合集成电光调制器理论分析与实验研究

对基于行波电极的硅-有机复合集成电光调制器进行研究,构建调制器的波导电极结构模型,分析特征阻抗和微波有效折射率对调制器频率响应的影响。通过对电极结构的仿真优化,完成调制器芯片的设计与制备,研究电光聚合物材料的片上极化工艺,得到高性能硅-有机复合集成电光调制器。对研制调制器电极的电学S(Scatter)参数进行测试,分析得到的电极特征阻抗和有效折射率与仿真设计结果基本相符。测试得到电光调制器的3 dB带宽大于50 GHz。     

基于偏置纳米线的石墨烯表面等离激元调制器

开发高性能的电光调制器对于构建片上光子回路非常重要.鉴于纳米线结构具备独特的电场横向束缚特点,设计一种基于纳米线的混合表面等离激元波导电光调制器,该调制器由偏置双硅纳米线、双石墨烯层以及置于双石墨烯层之间的银纳米线构成.利用二维时域有限差分算法计算分析结构参数对器件调制性能的影响.模拟结果表明,所设计的调制器在1550 nm的工作波长下可以实现较为出色的调制性能,其3 dB调制带宽高达250 GHz,调制深度和功耗分别高于0.15 dB/μm和低于11.5 fJ/bit,该调制器可为新一代高性能集成电光调制器的开发提供设计思路.     

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。     

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。     

锗硅合金脊形光波导的优化分析与设计

根据脊形光波导的基本设计要求，分析了锗硅合金脊形波导的结构参数对其光传播特性的影响，并优化设计了结构参数，其合理性得到了实验验证。     

高速异型掺杂的硅基槽波导调制器

针对硅基单端推挽调制器的pn结结电容大、调制效率低的问题,设计出一种基于异型掺杂和槽波导结构的硅基调制器。通过槽波导结构和L型掺杂增大了耗尽区与光场相互作用,与传统脊波导相比,在相同调制效率下,槽波导的结电容降低了24%,带宽提高了32%。采用T型轨道的电极实现阻抗和折射率的匹配,4 V偏压下调制带宽达到42 GHz,实现了峰峰值电压V_pp=2 V驱动下70 Gbit/s的OOK信号调制,眼图消光比达5.2 dB。     

基于有限元法的新结构LiNbO3电光调制器的分析与优化

对传统结构的LiNbO3电光调制器进行了改进,并用有限元法对改进后的电光调制器进行了分析计算,采用T形电极、脊波导和空气背槽的新型LiNbO3电光调制器在进行了结构尺寸优化后,相速完全匹配,带宽可达98 GHz,特性阻抗为52 Ω,损耗系数为0.464 dB/(cm·GHz1/2),半波电压为7.13 V,其性能远优于传统结构的调制器.     

Efficient evanescent coupling design for GeSi electro-absorption modulator

Efficient coupling from the silicon waveguide to the GeSi layer is the key to success in the GeSi electro-absorption （EA） modulator based on evanescent coupling. A lateral taper in the upper GeSi layer has room for increasing the modulating efficiency and alleviating the sensitivity of the extinction ratio （ER） and insertion loss （IL） to the length of the active region. The light behavior and the effect of the taper are explored in detail using the beam propagation method （BPM）. After optimization, the light can nearly be totally confined in the GeSi layer without any oscillation. The modulator with the designed taper can achieve low IL and high ER.     

硅衬底上锗硅合金光波导设计及工艺的优化考虑

报道用射频加热化学气相沉积法制备Ｓｉ／ＧｅＳｉ／Ｓｉ大断面单模脊形光波导中设计和工艺的进一步完善，ＧｅＳｉ合金层中Ｇｅ的含量Ｘ要满足脊形光波导是单模，光波导的数值，孔径接近单模光纤值，脊高小于临界厚度值等，计算表明兼顾上述三项要求应取ｘ＝１～３％，脊的高与宽受大断面及单模的制约。Ｓｉ的晶体结构使脊的二个腐蚀侧壁是斜坡，为此起始脊宽取５～６μｍ为宜；腐蚀液，抛光液的选取人保证脊则壁及波导面端的优良镜     

X-ray spherical wave scattering patterns of the epitaxial Si/GeSi/Si (001) heterosystem

The interference effects of x-ray diffraction topography in the Si/GeSi/Si (001) heterosystem have been investigated. This heterosystem is a film interferometer in which the GeSi solid solution layer of variable thickness serves as a separating gap. A topograph obtained for a 004 reflection (CuK _α radiation) using a spherically bent monochromator demonstrates both maxima of the pendulum solution observed for the case of a thin crystal (1) and interference fringes due to the variable thickness of the separation layer (2). The correlation of effects (1) and (2) with the successive extinction effect of interference maxima on the slope of the diffraction reflection curve is shown by the calculated topographs obtained for the different ranges of the angle of radiation incidence θ (200 and 1400″). The possibility of precisely determining the thickness of the crystal separation layer of an interferometer based on the indicated effect is demonstrated.     

Forming Dislocation Pairs in the Ge/GeSi/Si(001) Heterostructure

Physics of the Solid State - In the Ge/LTGe/GeSi/Si(001) heterostructures, the GeSi buffer layer remains pseudomorphic in a certain range of the heterostructure parameters and growth regimes, while...     

Specific features of plastic relaxation of a metastable Ge x Si1 − x layer buried between a silicon substrate and a relaxed germanium layer

Heterostructures Ge/Ge _x Si_{1 ? x} /Si(001) grown by molecular beam epitaxy have been investigated using atomic scale high-resolution electron microscopy. A germanium film (with a thickness of 0.5–1.0 μm) grown at a temperature of 500°C is completely relaxed. An intermediate Ge_0.5Si_0.5 layer remains in a strained metastable state, even though its thickness is 2–4 times larger than the critical value for the introduction of 60° misfit dislocations. It is assumed that the Ge/GeSi interface is a barrier for the penetration of dislocations from a relaxed Ge layer into the GeSi layer. This barrier is overcome during annealing of the heterostructures for 30 min at a temperature of 700°C, after which dislocation networks having different degrees of ordering and consisting predominantly of edge misfit dislocations are observed in the Ge/GeSi and GeSi/Si(001) heteroboundaries.     

Low-energy photoluminescence of structures with GeSi/Si(001) self-assembled nanoislands

The photoluminescence spectra of structures with self-assembled GeSi/Si(001) islands are investigated as functions of the growth temperature. It is shown that the shift of the peak of photoluminescence from islands toward lower energies on decreasing the growth temperature is due to the suppression of Si diffusion into islands and an increase in the fraction of Ge in islands. A photoluminescence signal from the GeSi islands is found in the region of energies down to 0.6 eV, which is considerably smaller than the band-gap width in bulk Ge. The position of the peak of photoluminescence from islands is described well by the model of a real-space indirect optical transition with account of the real composition and elastic strains of the islands. Mono-and multilayer structures are obtained with self-assembled GeSi/Si(001) nanoislands exhibiting a photoluminescence signal in the region 1.3–2 μm at room temperature.     

10 Gbit/s Silicon modulator and germanium detector chip-to-chip optical link

Experimental results of a high-speed silicon optical modulator based on carrier depletion in a pipin diode and Germanium photodetectors are presented. 10 Gbit/s data transmission is obtained for both optoelectronic devices, with for the optical modulator an extinction ratio (ER) higher than 8 dB and insertion loss (IL) lower than 6 dB and for Ge photodetector, a zero-bias operating at 10 Gbit/s. Finally, a 10 Gbit/s optical link combining Si modulator and Ge photodetector is demonstrated.     

Broadband 10 Gb/s operation of graphene electro‐absorption modulator on silicon

High performance integrated optical modulators are highly desired for future optical interconnects. The ultra‐high bandwidth and broadband operation potentially offered by graphene based electro‐absorption modulators has attracted a lot of attention in the photonics community recently. In this work, we theoretically evaluate the true potential of such modulators and illustrate this with experimental results for a silicon integrated graphene optical electro‐absorption modulator capable of broadband 10 Gb/s modulation speed. The measured results agree very well with theoretical predictions. A low insertion loss of 3.8 dB at 1580 nm and a low drive voltage of 2.5 V combined with broadband and athermal operation were obtained for a 50 μm‐length hybrid graphene‐Si device. The peak modulation efficiency of the device is 1.5 dB/V. This robust device is challenging best‐in‐class Si (Ge) modulators for future chip‐level optical interconnects.     

Infrared photoluminescence from GeSi nanocrystals embedded in a germanium–silicate matrix

We investigate the structural and optical properties of GeO/SiO₂ multilayers obtained by evaporation of GeO₂ and SiO₂ powders under ultrahigh vacuum conditions on Si(001) substrates. Both Raman and infrared absorption spectroscopy measurements indicate the formation of GeSi nanocrystals after postgrowth annealing at 800°C. High-resolution transmission electron microscopy characterizations show that the average size of the nanocrystals is about 5 nm. For samples containing GeSi nanocrystals, photoluminescence is observed at 14 K in the spectral range 1500–1600 nm. The temperature dependence of the photoluminescence is studied.     

Photoelectric properties of the GeSi/Si heterostructures with self-assembled nanoclusters grown by sublimation molecular beam epitaxy in a GeH4 medium

The photosensitivity (PS) spectra of the GeSi/Si(001) heterostructures with self-assembled nanoclusters grown by sublimation molecular beam epitaxy in a GeH₄ medium have been studied by photo-emf spectroscopy at the semiconductor/electrolyte junction (PSE) and by photo-emf and photocurrent spectroscopy of Schottky barriers including the temperature dependence of the PS spectra in the temperature range of 10–300 K. The bands related to the phonon assisted and phonon-less interband of spatially indirect optical transitions in the GeSi nanoclusters have been observed in the PS spectra even at 300 K. The scatter effect of the GeSi nanoclusters in size and/or in composition on the PS spectrum’s edge shape has been theoretically considered. The emission theory of the photoexcited carriers from the quantum wells of the GeSi/Si nanoclusters built-in to a Schottky barrier (p-tn junction, semiconductor/electrolyte junction) has been developed.