High-Power Diode-End-Pumped Slab Composite Tm:YLF Compact Laser

We design a continuous-wave Tm:YLF laser with a composite slab crystal end-pumped by two fiber-coupled laser diodes at room temperature. We achieve a maximum continuous wave output power of 105 W for the bonded slab Tm:YLF laser; the corresponding slope efficiency is 47.7% and the optical-to-optical conversion efficiency is 42.0% with respect to the incident pump power. The laser operated at 1,907.5 nm with a beam quality factor of M² ～3.2 at the highest output power.     

巡天光谱中拼接异常光谱的自动检测和异常分级方法

拼接异常是光谱在红蓝两端拼接区域表现出的光谱连续性差的一种现象。在LAMOST的光谱处理中,仪器的稳定性、观测条件以及获得的响应函数等问题都是造成拼接异常的原因。光谱拼接是否正常对于光谱发布等后续工作的质量有重要影响。提出一种拼接异常光谱的自动检测方法,有效地提高了工作效率。该研究可以为LAMOST数据提供一个自动的标记,来评价拼接质量,也可以为用户提供一个使用数据时的选择。该方法首先将待测光谱进行流量归一化、去除钠线等预处理,并将其分为红蓝两端;然后对红蓝两端分别进行拟合;最后对两条拟合曲线,选取一系列等波长间隔的点,计算在这些点处的流量差值,得到所有流量差值的均值,标准差,并且计算两条曲线积分面积的差值;基于上述统计量,提出了一个判断光谱是否异常及其异常程度的评价函数。大量的实验证明,该方法具有良好的拼接异常光谱检测效果。     

CCD紫外增强薄膜旋涂法工艺优化

在硅基探测器的入射窗上制备荧光下转换薄膜,是一种有效降低成本的紫外荧光增强技术。从理论上探讨了由聚二甲基硅氧烷与颜料黄101混合胶体的紫外荧光薄膜旋涂工艺参数与性能之间关系,搭建紫外荧光薄膜应用于光谱分析的性能测试实验平台,对紫外荧光增强薄膜旋涂工艺参数质量配比、旋涂转速进行优化。光谱分析探测器有两个主要指标,光谱响应灵敏度和光谱分辨率,分析与实验结果表明,利用旋涂法制备紫外增强荧光薄膜,旋涂转速将直接影响薄膜的厚度、表面粗糙度和荧光物质的分布,从而影响光谱分析系统的分辨率;紫外荧光增强薄膜的增强效率与荧光溶剂聚二甲基硅氧烷与荧光物质颜料黄101的质量比密切相关,质量比低无法满足对紫外响应效率的提高,但高质量比,荧光物质处在聚集态荧光自猝灭严重,也不利于增强薄膜的紫外响应效率。最终,在薄膜旋涂工艺优化的基础上,旋涂转速2 500～3 000 r·min-1,荧光物质与荧光溶剂质量比为7∶100制备出紫外荧光增强薄膜。汞灯特征光谱测试结果表明该薄膜313 nm紫外波长处探测响应灵敏度提高了1.6倍左右,对比分析镀膜前后特征光谱的半波带宽,镀制紫外增强荧光薄膜对其影响很小。     

Tens of GHz Tantalum pentoxide‐based micro‐ring all‐optical modulator for Si photonics

A tantalum pentoxide‐based (Ta₂O₅‐based) micro‐ring all‐optical modulator was fabricated. The refractive index inside the micro‐ring cavity was modified using the Kerr effect by injecting a pumped pulse. The transmittance of the ring resonator was controlled to achieve all‐optical modulation at the wavelength of the injected probe. When 12 GHz pulses with a peak power of 1.2 W were coupled in the ring cavity, the transmission spectrum of the Ta₂O₅ resonator was red‐shifted by 0.04 nm because of the Kerr effect. The relationship between the modulation depth and gap of the Ta₂O₅ directional coupler is discussed. An optimized gap of 1100 nm was obtained, and a maximum buildup factor of 11.7 with 84% modulation depth was achieved. The nonlinear refractive index of Ta₂O₅ at 1.55 μm was estimated as 3.4 × 10^?14 cm²/W based on the Kerr effect, which is almost an order of magnitude higher than that of Si₃N₄. All results indicate that Ta₂O₅ has potential for use in nonlinear waveguide applications with modulation speeds as high as tens of GHz.

     

Targeting Upconversion Nanoprobes for Magnetic Resonance Imaging of Early Colon Cancer

Colon cancer (CC) is one of the most common intestinal malignancies and is difficult to detect in its early stage by magnetic resonance imaging (MRI) with currently used contrast agents (CAs). The development of targeted CAs contributes to the early diagnosis of CC and thereby enables early intervention and timely therapy. Considering the outstanding performance of upconversion nanoprobes (UCNPs) in high‐performance MR and fluorescence imaging, a new type of nanoprobes with considerably enhanced imaging performance is developed herein. Carcinoembryonic antigen (CEA) antibody is conjugated onto the surface of UCNPs to achieve the targeted imaging of early CC tumors, which overexpress CEA. Both toxicity tests and histological/hematological examinations demonstrate the excellent biocompatibility of these CC‐targeting nanoprobes, which possess great potential for clinical application in the early diagnosis of CC.     

Proton beam writing of Nd:GGG crystals as new waveguide laser sources

Focused proton beam writing has been utilized to fabricate optical channel waveguides in Nd:GGG crystals. The 1?MeV proton beam irradiation creates a local modified region with positive refractive index changes at the end of the proton trajectory, in which the channel waveguide could confine the light field in a symmetric way. Room-temperature laser emission has been achieved at 1063.7?nm, with absorbed pump power of 61?mW (at 808?nm). The obtained slope efficiency of the Nd:GGG waveguide laser system is as high as 66%, which is, to our best knowledge, the highest value for integrated lasers from ion beam processed channel waveguide systems.     

熊猫型保偏光纤光栅温度和压力传感特性的实验研究

对熊猫型保偏光纤光栅的传感特性进行了深入的实验研究,采用温箱和压力罐分别进行了温度和压力传感特性的实验研究.实验结果表明:在0～2.5 MPa的压强范围内,熊猫型保偏光纤光栅两个偏振方向上的压力敏感系数分别为0.004 88 nm/MPa和0.003 52 nm/MPa;在15～50 ℃的温度范围内,两个偏振方向上的温度敏感系数为0.01018 nm/℃和0.008 8 nm/℃.该光纤光栅两偏振态对温度和压力的不同敏感特性可用于解决光纤光栅的交叉敏感问题.     

R值测量中强子事例选择的改进

强子事例的选择和强子探测效率是在BEPC/BES上进行R值测量的两项主要误差来源. 过去实验只选取等于或者大于2叉的强子事例, 因而0叉和1叉事例的丢失将导致强子事例数和强子探测效率的较大误差. 试图提出在R值测量中选取包含1叉强子事例在内的样本, 这将有助于更合理地调节强子事例产生器LUARLW的参数, 减小强子探测效率和R值测量的系统误差.     

原始数据中束流相关本底的分离

束流相关本底处理的不确定性是在BES/BEPC上进行R值测量的主要误差来源之一,提出从原始数据中分离出束流相关样本的新方法, 并把此样本用于调节强子产生器LUARLW的参数,以减小强子探测效率的系统误差, 提高R值的测量精度.