基于Moldflow的汽车散热格栅浇注系统优化设计

分析了浇注系统对成型大型格栅质量的影响。针对塑件原成型方案进行模拟分析,找出塑件表面产生熔接痕的原因。对浇注系统进行优化后,熔体充模过程均衡,型腔内各格栅端部几乎同时充满,避免了格栅上熔接痕的产生,型腔所需的充模压力不高、型腔温度分布比较均匀、塑件产生的翘曲变形较小,提高了塑件的外观质量。     

Viscosity of silica optical fibres characterized using regenerated gratings

The viscosity of an optical fibre over 1000–1150 °C is studied by inscribing an optical fibre Bragg grating that can withstand temperatures up to 1200 °C and monitoring fibre elongation under load through the Bragg wavelength shift. This optical interrogation offers high accuracy and reliability compared with direct measurements of elongation, particularly at lower temperatures, thus avoiding significant experimental error. An excellent Arrhenius fit is obtained from which an activation energy for viscous flow of E_a = 450 kJ mol^?1 is extracted; addition of an additional temperature-dependent pre-exponential does not change this value. The log plot of viscosity is found overall to be consistent with that reported in the literature for silica measurements on rods and beams, but substantially higher than past work reported for optical fibres. The annealing and strain temperatures for an optical fibre were derived as 1114 °C and 1010 °C. However, it is shown that, because regenerated gratings already involve a post-annealing process at higher temperature, the structures are equilibrated and much more relaxed compared with normal fibres, making viscosity measurements meaningful. This work highlights the need to stabilize components for operation in harsh environments before their application, despite some mechanical compromise. Given the increasing expectation of all-optical waveguide technologies operating >1000 °C, the need to study the behaviour of glass over the long term brings added significance to the basic understanding of glass in this regime.     

Influence of extrinsic and intrinsic parameters onto the formation of surface relief gratings in polar azo molecular glasses

Polar azo derivatives exhibiting stable glass-forming properties displayed efficient migration properties as thin films when subjected to interferential illumination, and formed time-stable and rewritable surface relief gratings as high as the initial film thickness. Intrinsic (film thickness, structure bulkiness) as well as extrinsic (laser fluence and polarization) parameters dramatically influenced the rate of the relief growth as well as the maximum relief amplitude. The superimposition of +45°/−45°-polarized beams unexpectedly conducted to a diffraction efficiency ten times as high as the combination of two p/p (parallel to the incident plane) polarized beams. The introduction of bulky anthryl Diels-Alder substituents showed net increase in the modulation amplitude due to the creation of large free volume around each azo unit, facilitating the azo migration within the less densely packed material.     

一种数字光栅无掩模光刻对准方法

针对数字微反射镜装置(DMD)无掩模光刻系统,提出并研究了一种数字光栅无掩模光刻对准方法,将硅片的微位移放大显示在数字光栅与硅片物理光栅叠加产生的叠栅条纹中。建立了基于DMD的数字光栅无掩模光刻对准模型,设计了对准标记以及具体的实现方案,并对模型进行了数值仿真和初步的实验验证。结果表明,采用频率可变、图像干净、具有良好周期性结构的数字光栅代替传统的真实掩模光栅,真正实现了零掩模成本;并且采用变频率数字光栅可以扩大测量范围,减小位移测量误差。最终可以实现深亚微米的对准精度,满足目前无掩模光刻对准精度的要求。     

光栅拼接技术研究进展

大面积衍射光栅的研制一直是研究的重大课题之一,同时大面积衍射光栅的制作以及获取是光栅研制的一个技术难点,啁啾脉冲放大(CPA)技术的出现更加加剧了对米级光栅的需求.由于大口径光栅制造技术难实现和经济代价高昂的限制,因此采用拼接的方法增大光栅的尺寸成为公认的经济有效的途径.详细介绍了光栅拼接的理论研究,并在此理论指导下,...     

Fabrication of biomimic GaAs subwavelength grating structures for broadband and angular-independent antireflection

We combine interferometric lithography and inductively coupled plasma etching to fabricate GaAs subwavelength grating (SWG) which mimics the moth eye structures. Through the modification of morphology parameters, including profile, height and packing fraction, tapered, high-aspect-ratio and closely-packed GaAs SWGs are obtained. The measurement of spectral reflectance of the fabricated SWGs shows that reflection has been dramatically reduced compared to the polished GaAs surface. Particularly, the optimized SWG structures exhibit an average reflection below 5% in the wavelengths ranging from 350 to 900 nm. Furthermore, the angular-independent property is demonstrated by measuring the reflectance versus varying angles of incidence at 532 and 632.8 nm wavelengths.     

Generation and transmission of dispersion tolerant 10-Gbps RZ-OOK signal for radio over fiber link

We proposed and demonstrated the generation and transmission of 10-Gbps return-to-zero ON/OFF keying (RZ-OOK) signal using a new technique without pulse carving at transmitter.The new technique is char...     

圆光栅测角系统信号细分电路设计

为提高圆光栅传感器对角度进行数字测量的精度和分辨力,使其更加广泛方便的应用于航天、机器人控制等领域中,设计了圆光栅角度测量系统及其测角信号移相电阻链细分电路,其将测得的原始的光栅正余弦信号施加在电阻链两端,在电阻链的接点上得到幅值和相位各不相同的电信号,经整形、脉冲形成后就能在信号的一个周期内获得若干计数脉冲,实现信号细分。该系统可精确的测量大方位、大俯仰、小方位、小俯仰四个轴系的角度位置。     

双芯片张光分插复用器的理论分析和设计

本文介绍了双芯光纤光分插复用器的工作原理、结构和功能,并利用耦合模理论分析了器件的工作特性,讨论了各部分参数对上／下路特性的影响。结果表明,为同时实现上路和下路功能,应尽可能使用强光纤光栅以缩短光纤的长度并同时维持高反射效率。     

光纤CDMA系统中FBG编—解码器的原理与应用

从光纤码分多址（OCDMA）系统的扩频特征和光纤布拉格光栅（FBG）的性能出发,对FBG编－解码器的编－解码原理进行了推导,并探讨了它实现跳频（FE）和直接序列扩频（DS）等OCDMA系统编－解码的方法,分析了FBG编－解码器对系统性能的影响。与光纤延迟线DS－OCDMA编－解码器和射光栅FE－OCDMA编－解码器的比较结果显示,FBG编－解码器在OCDMA（特别是FH－OCDMA）系统上具有功率效率高、信噪比性能好和最大数据传输速率高等方面的优点。