线-圆双偏振态光束抽运有机聚合物全光开关

为了有效降低偶氮苯聚合物薄膜全光开关信号的本底,提高全光开关信号的调制深度,利用线偏振光合成圆偏振光的原理,设计了一种新的线-圆双偏振态光束抽运光路。实验用532 nm光作为抽运光,632.8 nm的He-Ne激光作为探测光。532 nm的光先分为功率相等但偏振正交、相位差为π/2奇数倍的两束线偏振光,然后再合成一束抽运光。通过调制其中的一束来实现线偏振与圆偏振抽运光之间的转换,从而实现样品光致双折射的产生与擦除。以掺杂分散红1(DR1)的聚甲基丙烯酸甲酯薄膜(PMMA)为样品进行实验。结果表明,用此光路,样品全光开关信号的调制深度达到92%,远远高于传统的单一线偏振光束抽运光路的实验结果。     

基于SOA互增益调制双折射效应的全光2-4电平编码转换

提出了一种利用半导体光放大器(SOA)的互增益调制(XGM)的双折射效应实现全光2-4电平编码转换的方法.两路2-电平强度调制光信号正交偏振合波后,沿SOA的主轴进入,利用SOA的偏振调制实现被调制信号光的偏振调制,通过检偏输出4-电平强度调制光,从而实现2-4电平调制的编码转换.     

基于VO2相变的光控太赫兹调制器

基于VO2薄膜相变特性,通过在石英基底上制备VO2薄膜和亚波长金孔阵列,并在理论和实验上研究了金属孔阵列与VO2薄膜置于基底同侧和异侧的两种太赫兹(THz)调制器。系统研究了在光泵浦条件下两种样品的THz波的传输特性。结果表明,随着泵浦光功率的改变,两种结构的器件均可以实现对THz波强度的调制。对比分析两种结构器件的THz透射谱发现,紧邻金属孔阵列的金属相VO2能够有效地抑制THz表面等离子体的局域透射增强效应,使调制器的调制深度得到显著增强,这对基于相变材料调制器的设计具有重要意义。     

毫秒有机聚合物薄膜全光开关

用聚甲基丙烯酸甲酯(PMMA)和偶氮染料DRl以一定的比例混合，制成各向同性均匀薄膜样品。用经斩波器调制的线偏振氩离子激光(514nm，CW)作用样品产生光致双折射。作为探测光的线偏振氦氖激光(633nm，CW)经过样品，在与其原来偏振方向垂直的检偏器后的透射光强强度受控制光的调制作用，实现了光控光的全光开关效应。通过改变控制光的光功率及薄膜样品的温度。对样品的开关响应速度和开关调制深度进行了研究。在一定的实验条件下，用毫瓦量级的控制光功率实现了几个毫秒的开关响应速度和60％以上的开关调制深度。     

微纳光纤耦合器光致热引起的全光强度调控特性

对微纳光纤耦合器(OMC)光吸收致热引起的全光强度调控特性进行了理论分析和实验研究。理论分析结果显示,OMC全光强度调控器件的调制响应效率与OMC腰区长度、抽运光在OMC腰区的损耗系数及抽运调制光强成正比,而与OMC腰区耦合光纤的半径成反比。通过实验将强度调制的980nm抽运光注入OMC以加热其腰区,实现了对OMC传输的1550nm工作光的全光调控功能。在百微瓦量级的调控光功率作用下,OMC全光强度调控器件即可实现整周期、大调制深度的强度调制,且在较小调制光功率下,调制响应信号幅度与调制信号幅度呈线性响应关系。OMC光热调控最小响应调制光功率为几十微瓦量级。研究成果为开发基于OMC光致热效应的光衰减、光开关及强度调制器等全光功能器件提供了实验数据,并为微纳光子集成光路热稳定性管控及片基量子通信系统安全性研究提供了可借鉴的研究方案。     

光栅成像位置传感器中的偏振调制技术

提出了一种用于光栅成像位置传感器的偏振调制技术,利用米勒矩阵对其调制原理进行了详细的分析。该偏振调制器主要由起偏器、萨伐尔板、两块1/4波片、光弹调制器和检偏器构成。起偏器、萨伐尔板置于探测光栅之前,在探测光栅位置上形成两个错位的偏振方向正交的像光栅。两块1/4波片、光弹调制器和检偏器置于探测光栅之后,实现对莫尔信号的高频调制。该偏振调制技术消除了光源光强波动和电路增益变化引入的测量误差,抑制了杂散光、探测器噪声对测量结果的影响。实验验证了该偏振调制技术的有效性,结果表明这一技术使光栅成像位移传感器获得了优于12 nm的重复测量精度。     

核壳结构偶氮聚合物的全光开关效应研究

分别用主客掺杂法和种子乳液聚合法制备了含相同浓度偶氮染料分散红4-(2-hydroxyethyl) ethylamino-2-chloro-4-nitroazobenzene(Disperse Red 13,DR13)的聚甲基丙烯酸甲酯poly(methyl methacrylate)(PMMA)均匀薄膜样品.用经斩波器调制的线偏振氩离子激光(514 nm,CW)作用于样品产生光致双折射.作为探测光的线偏振氦氖激光(633nm,CW)经过样品,通过与原来偏振方向垂直的检偏器的透射光强强度的调制,实现了光控光的全光开关效应.研究比较了两种样品在控制不同光功率下的光致双折射效应和全光开关效应,比较发现用种子乳液聚合法制备的具有核壳结构的样品在控制光功率、开关时间及开关调制深度等方面均优于主客掺杂样品.     

基于电吸收调制器的全光开关门模型和实验研究

全光开关门是全光3R再生、全光解复用、全光逻辑门和全光波长变换的重要组成模块,而基于电吸收调制器(EAM)的全光开关门具有偏振无关和码型效应小等优点.依据光生载流子的输运方程,建立了体材料EAM中的交叉吸收调制(XAM)模型.通过该模型利用时域有限差分法,研究了EAM在高功率超短光脉冲抽运作用下形成的开关门特性,对不同EAM偏置电压、抽运光功率和脉冲宽度下的开关门进行了分析.同时.进行了开关门特性与偏置电压大小和抽运脉冲功率之间关系的实验研究.实验结果与理论预期相符合.EAM光开关用于光3R再生,使40 Gb/s残余色散或偏振模色散恶化信号得到再生.     

基于微波光子六倍频的光载无线通信系统

构建了基于微波光子倍频的光载无线传输系统。基于偏振调制器实现了六倍频光毫米波产生,利用马赫增德尔调制器实现了QAM信号调制并进行光载无线传输,测试了41.5GHz QAM信号调制和10km光载无线传输光纤传输之后的QAM信号星座图。该系统实现了远距离音视频或高清数字信号传输。     

基于偏振控制的Sagnac环负系数微波光子滤波器

为了克服正抽头系数低通滤波的限制,满足光载无线通信(ROF)、无线通信等系统对带通滤波器的需要,提出了一种新的负系数带通微波光子滤波器结构。系统采用了一种偏振敏感的电吸收调制器,其横向电场(TE)和横向磁场(TM)方向上具有不同的调制系数,在小信号调制下仍为线性调制。通过旋转偏振控制单元的波片,改变其快轴与TE方向的夹角,可以得到任意偏振态的转换。当偏振控制单元由两个旋光方向相反的法拉第旋光片和一个1/2波片组合时实现了负系数滤波,和一个1/4波片组合时得到了正系数滤波。     

Low-loss electrooptic BaTiO/sub 3/ thin film waveguide modulator

A strip-loaded electrooptic waveguide modulator based on an epitaxial BaTiO/sub 3/ thin film was fabricated and characterized for the first time. The strip-loaded waveguide structure greatly improves waveguide propagation and polarization-dependent loss performance. A propagation loss of 1.1 dB/cm and polarization dependent loss of 0.1 dB/cm were measured. The electrooptic waveguide modulator exhibited a half-wave voltage-interaction length product of 4.5 V /spl middot/ cm at a wavelength of 1542 nm. The measured effective electrooptic coefficient of the as-grown BaTiO/sub 3/ waveguide modulator was 38 pm/V. The experimental results indicate that a strip-loaded thin film waveguide modulator is suitable for photonic applications.     

Polarization Processes in Thin Layers of Amorphous MoS2 Obtained by RF Magnetron Sputtering

Semiconductors - The polarization processes in thin layers of amorphous molybdenum disulfide MoS2 are studied by dielectric spectroscopy techniques. The process of dipole-relaxation polarization is...     

Synthesis of two-dimensional/one-dimensional heterostructures with tunable width

Two-dimensional/one-dimensional (2D/1D) heterostructures as a new type of heterostructure have been studied for their unusual properties and promising applications in electronic and optoelectronic devices.However,the studies of 2D/1 D het-erostructures are mainly focused on vertical heterostructures,such as MoS2 nanosheet-carbon nanotubes.The research on later-al 2D/1D heterostructures with a tunable width of 1D material is still scarce.In this study,bidirectional flow chemical vapor de-position (CVD) was used to accurately control the width of the WS2/WSe2 (WS2/MoS2) heterostructures by controlling reacting time.WSe2 and MoS2 with different widths were epitaxially grown at the edge of WS2,respectively.Optical microscope,atomic force microscope (AFM),and scanning electron microscope (SEM) images show the morphology and width of the heterostruc-tures.These results show that the width of the heterostructures can be as low as 10 nm by using this method.The interface of the heterostructure is clear and smooth,which is suitable for application.This report offers a new method for the growth of 1D nanowires,and lays the foundation for the future study of the physical and chemical properties of 2D/1D lateral heterostruc-tures.     

Q-switched pulse generation in a bidirectionally pumped EDFL utilizing Lu2O3 as saturable absorber

In this paper, we have successfully demonstrated a Q-switched pulse generation utilizing lutetium oxide (Lu2O3) thin film based saturable absorber (SA) in all-fiber erbium-doped fiber laser (EDFL) cavity with a bidirectional pumping. The Lu2O3 powder is mixed with isopropyl alcohol (IPA) solution before we add polyvinyl alcohol (PVA) as our host polymer to make the Lu2O3 into a thin film. By inserting the Lu2O3-PVA thin film into a bidirectional pumped EDFL cavity, a stable Q-switched pulse is realized with repetition rate in a range of rose from 43.67 kHz to 57.74 kHz whereas the pulse width decreased from 14.48 µs to 11.20 µs. This result indicates that the Lu2O3 can be implemented as an SA device in an EDFL as it owns a linear absorption of around 3 dB at 1 567 nm.     

Ferroelectric characteristic of group IV elements added SrBi2Ta2O9 thin films

The SrBi₂Ta₂O₉ (SBT) thin film added IV group elements was fabricated on the Pt/Ti/SiO₂/Si substrate by the metal–organic decomposition (MOD) method, the Pt electrode was deposited on the SBT thin film by the DC spattering method. The electric properties of the ferroelectric capacitor were measured. The remanent polarization and the relative dielectric constant of the SBT thin film have decreased, according to the amount of IV group elements addition. The IV group elements added SBT thin film with low relative dielectric constant and low remanent polarization is suitable for the application of the ferroelectric gate FET type memory.     

氧等离子体对少层MoS2及其场效应晶体管的影响研究

通过氧等离子体对MoS2材料及其场效应晶体管进行处理,用AFM、拉曼光谱、XPS和I-V测试对材料和器件性能进行表征,系统研究了氧等离子体对MoS2材料及其器件性能的影响。实验结果表明,氧等离子体处理可以有效去除MoS2材料和器件制备过程中引入的有机杂质,将MoS2的表面粗糙度降低到了0.27 nm。同时氧等离子体将表层MoS2氧化成MoO3,降低了器件接触区域MoS2与金属之间的费米能级钉扎效应,使器件开关比高达3.3×10^6。对MoS2器件沟道进行处理时,氧离子穿过MoO3插入到MoS2晶格中从而对沟道形成p型掺杂。     

单层硫化钼的研究进展

单层硫化钼(MoS2)是具有直接帯隙1.8 eV的二维半导体,因其特殊的六方晶系层状结构,而具有优异的物理和化学性质。简要介绍了MoS2材料的几种主要制备方法:如高温硫化法、水热法以及表面活性剂促助法等,讨论了各种制备方法在国内外的研究现状及优缺点。给出了单层MoS2在晶体管、集成电路、逻辑运算等方面的一些应用。与硅晶体管相比其晶体管体积更小、更省电,并可减少短通道效应,电流开/关比例高于1010。这些应用说明了其可被广泛应用于未来的纳米电子器件。最后,对MoS2未来的发展方向进行了展望,认为工艺制备方法有待进一步改善,单层MoS2的应用领域也有待进一步深入拓展。     

Q-switched pulse generation with lutetium oxide absorber

A lutetium oxide (Lu2O3) film was proposed and demonstrated for Q-switching operation at 1.55 µm region. It was obtained by solving Lu2O3 powder into isopropyl alcohol and mixing the solution into polyvinyl alcohol (PVA) solution to form a composite precursor solution via stirring, sonicating, and centrifuging processes. The thin film was formed through a drop and dry process and a small piece of this film was integrated into erbium-doped fiber laser (EDFL) cavity to modulate the cavity loss via Q-switching mechanism for pulse generation. The Q-switched laser operated at 1 565 nm with the repetition rate of 75.26 kHz as the pump power was raised to the maximum value of 145.83 mW. The maximum pulse energy of 41.85 nJ was recorded at 145.83 mW pump power. The mode-locked pulse operated at 968.5 kHz with a pulse width of 510 ns was also realized in an extended EDFL cavity. The simple and cost-effective laser should have various applications including material processing, sensing and biomedical areas.     

Structural and Electrical Characters of Ba0.6Sr0.4TiO3/La0.5Sr0.5CoO3 Thin Films by Plus Laser Deposition

Epitaxial Ba0.6Sr0.4TiO3 (BST) thin films were deposited on LaAlO3 (LAO) substrates with the conductive metallic oxide La0.5Sr0.5CoO3 (LSCO) film as a bottom electrode by pulsed laser deposition (PLD). X-ray diffraction ~2 and Ф scan showed that the epitaxial relationship of BST/LSCO/LAO was [001] BST//[001] LSCO//[001] LAO. The atomic force microscope (AFM) revealed a smooth and crack-free surface of BST films on LSCO-coated LAO substrate with the average grain size of 120 nm and the RMS of 1.564 nm for BST films. Pt/BST/LSCO capacitor was fabricated to perform CapacitanceVoltage measurement indicating good insulating characteristics. For epitaxial BST film, the dielectric constant and dielectric loss were determined as 471 and 0.03, respectively. The tunabilty was 79.59% and the leakage current was 2.6310-7 A/cm2 under an applied filed of 200 kV/cm. Furthermore, it was found that epitaxial BST (60/40) films demonstrate well-behaved ferroelectric properties with the remnate polarization of 6.085 C/cm2 and the coercive field of 72 kV/cm. The different electric properties from bulk BST (60/40) materials with intrinsic paraelectric characteristic are attributed to the interface effects.     

Effect of titanium dioxide (TiO2) seed layer on the phase composition of 0.7Pb (Mg1/3Nb2/3)O3-0.3PbTiO3 film prepared by pulsed laser deposition

Lead-magnesium niobate-lead titanate (PMN-PT) thin films with and without the TiO₂ seed layer were deposited on Pt/Ti/SiO₂/Si substrates through pulsed laser deposition. The study aimed to characterize the effect of the TiO₂ seed layer on the phase composition and properties of PMN-PT film. Without the TiO₂ seed layer, the pure perovskite phase could be obtained in the thinner PMN-PT film while with the TiO₂ seed layer, the pure perovskite phase was formed in the thicker PMN-PT film. The ferroelectric properties of PMN-PT films with the TiO₂ seed layer were exhibited. As a result, the maximum amount of remnant polarization reached the amount of 32 μC/cm² for the PMN-PT thin film with the TiO₂ seed layer.