基于图像处理的光学谐振腔自准直研究方法

针对我国氧碘化学激光器输出能量不断提高的情况下,主要限制光束质量的因素之一是出光过程中的光腔失调,提出了一种基于图像处理的光学谐振腔自准直研究方法。该研究方法利用氦氖穿腔光通过凹腔镜中心孔,并在凸腔镜后方放置工业相机,在屏幕上方形成一个干涉同心圆环。通过借助OpenCV库中二值化、霍夫圆检测等图像处理的方法,获得干涉同心圆环的圆心坐标,再通过以圆心为中心将图像分成上下左右四个部分,通过判断这四部分亮点像素的数量差值来预估干涉同心圆环的偏移状态,进而获得空腔条件下光学谐振腔发生变化的理论判据。实验结果表明,该方法可以获得相当精准的光学谐振腔失调判据,其失调判据选取左右亮点像素差值30 000,上下亮点像素差值45 000,为今后失调判据与步进电机自动调腔的结合做好充足的准备。

     

有机发光器件的磁电导效应

制备了基于三(8-羟基喹啉)铝(tris-(8-hydroxyquinoline) aluminum (III), Alq₃) 的有机发光二极管, 并在不同偏压下测量了器件的室温磁电导效应.在小偏压下, 发光器件展示出明显的负磁电导效应.偏压增加后, 磁电导由负值变为正值, 出现了正负转变的现象. N, N'-二苯基-N, N'-(1-萘基)-1, 1'-联苯-4, 4'-二胺(N, N′-Di(naphthalen-1-yl)-N, N′ diphenyl-benzidine, NPB) 与铜酞菁 (Copper phthalocyanine, CuPc) 单极器件磁电导的测量结果表明, 发光器件在小偏压下的负磁电导效应来源于器件中的CuPc层. 双极电流的磁电导效应可用电子-空穴对模型进行解释, 而单极电流的磁电导效应可归因于器件中的极化子-双极化子转变. 在注入电流的变化过程中, 发光器件的正负磁电导转变是两种机理共同作用的结果.     

Irradiation induced changes in small angle grain boundaries in mosaic Cu thin films

We studied the effect of irradiation on small angle grain boundaries in mosaic structured Cu thin films. The films showed a decrease in mosaic spread via a narrowing of the full width at half maximum in XRD rocking curves and a smaller minimum yield of RBS channeling after irradiation. These data indicate the irradiation decreased the misorientation angles between mosaic blocks separated by small angle grain boundaries. Mechanisms involving interactions between grain boundary dislocations and irradiation induced defects are discussed.     

神光Ⅱ终端光学组件的频率变换逆问题研究

在激光惯性约束核聚变(ICF)精确打靶中,对激光束变换、整形和控制要求苛刻,通过数字在线操控技术能够在线实现激光系统的自动校准,而频率变换是数字在线操控技术中的关键一环。在不进行逼近迭代计算的情况下,基于可逆的傅里叶变换和龙格-库塔算法,对神光II终端靶场系统中负单轴晶体KDP的"I+II"类频率变换的逆问题进行了探讨和相应的算法研究,并给出了对应的模拟计算结果。最后,与神光装置运行的实验数据进行比对,验证了频率变换逆问题算法的正确性和稳定性。     

高速摄影在流体动力学不稳定性研究中的应用

用高速摄影技术研究了高压气体膨胀驱动空气-水界面的瑞利-泰勒不稳定性,获得了空气-水界面的不稳定性清晰图像,得到气炮尖顶运动速度及湍流混合层高度增长速度与时间关系曲线。在横式激波管上用高速纹影诊断技术研究了激波作用空气-SF6界面的里克特迈耶-梅什科夫不稳定性,初步获得了实验图像,可清晰显示混合区变化过程。     

Potential PDP phosphors with strong absorption around 172 nm: Rare earth doped NaLaP2O7 and NaGdP2O7

NaLaP₂O₇ and NaGdP₂O₇ powder samples are prepared by solid-state reactions at 750 and 600 °C, respectively, and the VUV-excited luminescence properties of Ln³⁺ (Ln=Ce, Pr, Tb, Tm, Eu) in both diphosphates are studied. Ln³⁺ ions in both hosts show analogous luminescence. For Ce³⁺-doped samples, the five Ce³⁺ 5d levels can be clearly identified. As for Pr³⁺ and Tb³⁺-doped samples, strong 4f-5d absorption band around 172 nm is observed, which matches well with Xe-He excimer in plasma display panel (PDP) devices. As a result, Pr³⁺ can be utilized as sensitizer to absorb 172 nm VUV photon and transfer energy to appropriate activators, and Tb³⁺-doped NaREP₂O₇(RE=La, Gd) are potential 172 nm excited green PDP phosphors. For Tm³⁺ and Eu³⁺-doped samples, the Tm³⁺-O²⁻ charge transfer band (CTB) is observed to be at 177 nm, but the CTB of Eu³⁺ is observed at abnormally low energy position, which might originate from multi-position of Eu³⁺ ions. The similarity in luminescence properties of Ln³⁺ in both hosts indicates certain structural resemblance of coordination environment of Ln³⁺ in the two sodium rare earth diphosphates.     

用于双色全息存储(Fe,Cu)∶LiNbO3晶体的参量优化计算

在确定Cu在LiNbO3晶体中对应于365 nm和633 nm的激发系数、复合系数、光伏系数的基础上,采用龙格库塔(Runge-Kutta)数值方法理论研究了双掺杂(Fe,Cu)∶LiNbO3晶体的深浅能级的掺杂组分比、氧化还原状态对双色全息存储的记录灵敏度和动态范围的影响,并探讨了同时取得尽可能大的灵敏度和动态范围的晶体条件。结果表明,为了同时得到较大的记录灵敏度和动态范围,在实际应用中选用浅能级掺杂浓度为5.0×1025m-3,深能级掺杂浓度为3×1024~3×1025m-3之间的弱氧化晶体是合适的。     

体全息存储中几种软件降噪方法的综合使用

针对体全息存储系统中常见的几种噪声源 ,即大尺度噪声、像素间干涉噪声以及突发性随机噪声的特点 ,分别采用减背景、页内均衡化和所罗门编码三种软件方法予以补偿。在实验中 ,通过将三种方法有机地结合在一起 ,获得了明显的降噪效果 ,误比特率由初始的 1 0 - 2 降低到 1 0 - 4以下。     

Interaction of longitudinal phonons with discrete breather in strained graphene

We numerically analyze the interaction of small-amplitude phonon waves with standing gap discrete breather (DB) in strained graphene. To make the system support gap DB, strain is applied to create a gap in the phonon spectrum. We only focus on the in-plane phonons and DB, so the issue is investigated under a quasi-one-dimensional setup. It is found that, for the longitudinal sound waves having frequencies below 6 THz, DB is transparent and thus no radiation of energy from DB takes place; whereas for those sound waves with higher frequencies within the acoustic (optical) phonon band, phonon is mainly transmitted (reflected) by DB, and concomitantly, DB radiates its energy when interacting with phonons. The latter case is supported by the fact that, the sum of the transmitted and reflected phonon energy densities is noticeably higher than that of the incident wave. Our results here may provide insight into energy transport in graphene when the spatially localized nonlinear vibration modes are presented.     

Influences of travelling magnetic field on the dendritic structures of Sn–1.8Cd peritectic alloy during directional solidification

The effects of melt flow driven by a travelling magnetic field (TMF) on solidification structures of Sn–1.8 wt.% Cd peritectic alloy have been investigated numerically and experimentally. Numerical results indicate that the flow velocity at the solid–liquid interface under a downward TMF is smaller than that under an upward TMF. The experimental results show that the growth directions of dendrites are chaotic, and several crotches among the dendrites are observed at the solid–liquid interface in the case of no field. It is concluded from TMF results that the ordered growth of dendrites at two different directions occurs, and only one crotch among the dendrites appears at the solid–liquid interface. The location of the crotch gradually approaches the interface center with increasing magnetic field intensity (B≤10.3 mT). Moreover, the growth of high-order branches occurs at the crotch under a downward TMF. A simple model is established for explanation and it well corresponds to the experimental results.