双掺(Tm3+,Tb3+)LiYF4激光器1.5 μm波长激光阈值分析

由速率方程推出了双掺（Tm^3 ,Tb^3 ）离子准四能级系统的激光阈值解析式，讨论了Tm^3 和Tb^3 离子之间的相互作用。分析了1.5μm波长附近的激光阈值和Tm^3 、Tb^3 离子的掺杂原子数分数及晶体长度的关系。结果表明，对于对应Tm^3 离子^3H4→^3F4跃迁的约1.5μm波长的激光，激活离子Tm^3 的掺杂原子数分数过大时，交叉弛豫作用将使系统阈值迅速增加。Tb^3 离子的加入，一方面能抽空激光下能级，起到降低阈值的作用；另一方面亦减少了激光上能级的寿命，使阈值升高。故Tb^3 离子有最佳掺杂原子数分数。对于Tm原子数分数为y=0.01的Tm:LiYF4晶体，Tb^3 离子的最佳掺杂原子数分数为0.002左右，同时表明，激光阈值与晶体长度有关。最佳晶体长度与Tm^3 、Tb^3 离子的掺杂原子数分数以及晶体的衍射损耗和吸收损耗有关。     

用BBO晶体产生196～228nm波长的紫外辐射

本文报道了用BBO晶体通过混频产生196～228nm可调谐紫外辐射的研究结果.产生200nm及222nm的量子转换效率分别为12%及23%,与理论计算值基本相符.     

CdTe/ZnSe核壳量子点免疫层析试纸条检测克伦特罗的研究

采用巯基丁二酸作为表面修饰剂,水相法合成水溶性的CdTe/ZnSe核壳量子点,然后在N-羟基琥珀酰亚胺(NHS)的作用下,将CdTe/ZnSe核壳量子点与抗克伦特罗多克隆抗体(Anti-CLE pAb)连接。通过凝胶电泳和斑点杂交实验,验证CdTe/ZnSe核壳量子点与Anti-CLE pAb连接成功,并且CdTe/ZnSe-Anti-CLE pAb偶联物能识别克伦特罗-BSA抗原(CLE-BSA)。光谱分析表明,量子点与抗体连接后荧光增强,荧光峰位从628nm红移至635nm。将合成的CdTe/ZnSe-Anti-CLE pAb偶联物作为指示克伦特罗(CLE)分子的荧光标记物,制备出一种用于检测CLE的免疫层析试纸条,其最低检测量可达1μg/L。与ELISA法的对比实验表明,此试纸条能应用于CLE残留的快速检测。     

Ce:BaTiO3晶体中两个深陷阱能级引起的光折变光栅暗衰减特性

对Ce:BaTiO3晶体中光折变光栅的暗衰减特性进行了实验研究，观测到了晶体禁带中的Fe离子和Ce离子两个深陷阱能级同时参与了光折变过程。在单深能级模型和浅－深能级模型的基础上，提出了简化的双深能级模型，并根据该模型定量地分析了Fe离子和Ce离子每个深陷阱能级在不同光栅波矢、不同光栅写入光强时对总空间电场以及光折变光栅的贡献。     

对晶体光损伤阈值测量的一种新方法的研究

提出一种测量晶体光损伤阈值的新方法,即确定激光横向功率密度的空间分布,利用晶体的激光损伤斑点半径,直接计算出晶体光损伤阈值,并给出入射激光为高斯光束时晶体损伤阈值与其损斑半径的关系。以提拉法生长的掺镁铌酸锂(MgO：LiNbO3)晶体为研究对象,用该方法测量其损伤阈值,得到了定量结果且所得数据与文献已报道的规律相符。分析得出同样激光条件下．损斑半径越大的晶体其光损伤阈值越小的结论,指出该方法同样适用于其他晶体或非高斯光束条件下光损伤阈值的测量并对具体作法进行了讨论。该测量方法弥补了常用测量方法只能定性或半定量的不足,可用于晶体抗光损伤阈值的精确测量。     

ANALYSIS OF LASING PERFORMANCES OF Yb3+-DOPED YAG, FAP, KYW CRYSTALS

The Yb³⁺ laser emitting at a 1.03μm wavelength has been evoking strong interest recently due to its advantages of long fluorescence lifetime, broad absorption band and the fact that it never shows concentration quenching. On the other hand, as a laser of three-level system it has, in general, a relatively high threshold power, which makes it important to seek some suitable host crystals to reduce this. Here, we present a comparison of the lasing performances of Yb³⁺-doped YAG [Y₃Al₅O₁₂], FAP [Ca₅(PO₄)₃F] and KYW [KY(WO₄)₂] crystals, including threshold power and slope efficiency, with those of the Nd:YAG laser based on the threshold formula of three-and four-level systems deduced by the authors. The results show that the Yb³⁺ laser can output a power larger than the Nd:YAG laser does in the case of comparably higher pumping power, if the length of the lasing rod and the concentration of the active ions satisfy some conditions. The theoretical results are also close to the experimental results reported.     

异烟肼-烟酰胺-丁二酸三元共晶的振动光谱检测与分析

药物共晶是指将活性药物成分(API)与共晶形成物以非共价键的形式组合在一起,形成具有特殊晶胞结构的晶体。共晶可以在不改变API药理性质的情况下有效改善其理化性质,近年来被大量报道。三元共晶指由三种组分构成的晶体,相较于传统的二元共晶,三种组分形成的结构更加复杂,分子间的氢键形式更加多样,合成和分析的难度都大大提高。采用溶剂蒸发法制备了异烟肼-烟酰胺-丁二酸三元共晶,并通过太赫兹时域光谱技术(THz-TDS)对其进行定性分析,证实了可以通过此种方法制备共晶。同时为研究共晶中的氢键合成元形式,结合密度泛函理论(DFT)对共晶中可能的氢键形式进行了模拟,模拟结果与实验结果较为吻合。在此基础上,对三元共晶的氢键合成元形式和振动模式进行了分析。     

Ce∶BaTiO_3中光折变光栅衍射效率上升现象及分析

在对Ce∶BaTi O3晶体进行双光束干涉光折变光栅暗衰减特性的实验研究中,发现了暗条件下光折变光栅归一化衍射效率长时间上升的异常现象:在e光偏振、大入射角度产生光折变光栅的实验中,衍射效率在长逾8 h的时间内持续上升.而在e光干涉、小入射角度和o光干涉时均未出现衍射效率长时间上升的现象.分析认为:由于自泵浦位相共轭光的产生和晶体中的两个深能级参与了光折变过程,形成了衰减速度不同、光栅方向垂直的两个光栅,导致了暗衰减时衍射效率的长时间上升.     

Anomalous behaviour of long-time increase in diffraction efficiency of photorefractive grating in Ce：BaTiO3 in dark

Anomalous long-time increase of the diffraction efficiency is observed in dark-decay experiments of photorefractive gratings in Ce：BaTiO3. It is deduced that a phase-conjugate beam is induced by the writing beam at acute angle to the ＋c axis of the crystal and it interferes with the other writing beam to form a second grating which is perpendicular to the first grating formed by the interference between two writing beams. The rising behaviour of the diffraction efficiency results from the different decay rates of these two photorefractive gratings. Furthermore, a simplified model of two gratings, both induced by two deep traps, is proposed to account for this phenomenon and the fitting results agree well with the experimental results.