Simple Nd:YAG laser generates vector and vortex beam

We report a simple Nd:YAG laser that emits radially polarized beam with helical wavefront. The laser cavity consists of a piece of laser crystal and a plane output coupler, and there is no additional polarization component inside it. The pump light is converted into annular profile through de-focal coupling into a multi-mode fiber. For the continuous-wave(CW) operation, the laser emits radially polarized vortex beam, and it is observed that the helical wavefront of the laser beam is switched from right handedness to left handedness when the output coupler is tilted slightly. For the Q-switched operation under the insertion of a Cr4t:YAG saturable absorber inside the cavity, we obtain radially polarized outputs with left-handedness helical wavefront. By tilting the laser crystal slightly, the laser output switches to azimuthal polarization at pump power larger than 4.5 W and left-handedness helical wavefront of laser beam is preserved.     

抗爆型聚脲涂层的性能及其抗爆机理

通过广角X射线衍射仪、差示扫描量热法实验、扫描电子显微镜以及聚脲喷涂钢筋混凝土板的接触爆炸实验,研究了Qtech T26抗爆型聚脲(T26聚脲)的力学强度、分子结构及热性能,分析了有无涂层钢筋混凝土板的宏观形貌及涂层的微观形貌,考察了T26聚脲喷涂钢筋混凝土板的抗爆能力和防护机理。结果表明:T26聚脲的拉伸强度达到25.4 MPa,断裂伸长率为451.9%;其分子链中软段与硬段之间排列有序,微晶区结晶度为24.11%;软段玻璃化转变温度为-44.9℃,硬段玻璃化转变温度为36.5℃,呈现出一定的微相分离形态。爆炸实验后,无涂层钢筋混凝土板的迎爆面出现较大凹坑,背爆面被震塌,混凝土破碎;而对于有涂层的钢筋混凝土板,其迎爆面出现较小凹坑,迎爆面涂层除了因瞬间高温而导致的聚脲软化外,爆炸反射波的稀疏拉伸作用使聚脲材料发生破坏,聚脲涂层被撕裂,而背爆面则由于聚脲涂层削弱了稀疏拉伸波的作用,从而保护混凝土材料不被破碎,避免爆炸碎片飞溅。     

N-(6-甲基-2-亚甲基吡啶)-( )-樟脑亚胺体系的不对称烷基化反应

目前,不对称合成光学活性化合物取得了较大进展,不对称合成α-氨基酸、β-氨基醇、α-取代苄胺的报道很多。但是,不对称合成生物碱类物质——α-取代氨甲基吡啶类化合物还未见文献报道,而此类化合物有潜在的应用前景。为此,我们以( )-樟脑为手性试剂     

（＋）－樟脑硫亚胺的合成

合成了四种含樟脑巯基手性助剂的光学活性的硫亚胺化合物。     

高强透明纤维素材料的制备、结构与性能

以杉木为原料,通过两步法(脱木质素和加压干燥)制备出高强透明纤维素材料.其最高透光率为68%(600 nm),雾度达到93%(600 nm),最大拉伸强度和弹性模量分别为362 MPa和9. 5 GPa.采用扫描电子显微镜(SEM)、X射线衍射(XRD)、热失重分析(TGA)、紫外-可见(UV-Vis)分光光度计和拉伸试验仪等对高强透明纤维素材料的结构、纤维素晶型、力学性能、热稳定性及光学性能进行了表征和分析,初步解析了该纤维素材料具有较高透光率和抗张强度的原因.     

Generation of Laguerre-Gaussian beam from end-pumped and c-cut Nd:YVO4 laser

We demonstrate an end-pumped,c-cut Nd:YVO4 laser that emitted first-order Laguerre-Gaussian(LG01) beam by adjusting the position of focused pump beam relative to laser crystal.The pumping light reached the laser crystal has circular and solid intensity profile.The laser is compact and stable,and the obtained LG01 beam power reaches 202 mW with ～25% slope efficiency.     

Transverse mode transition and LG01-mode generation in an end-pumped Nd：YV04 laser

A laser-diode end-pumped Nd：YVO4 crystal laser is demonstrated to emit the first-order Laguerre- Gaussian （LGm） mode with 502-mW laser power and 22% slope efficiency. Tile LGm-mode is lased only when the pumping area locates in the central part of the laser crystal＇s front surface, and thereafter the symmetrical LGm-HGol-TEM00 mode transition happens when laser crystal is moved laterally inside several-tens-micron area. The possible mechanism responsible for the phenomenon of symmetrical mode transition is also discussed.     

释放性微胶囊/荧光粉复相涂层的制备及其防污性能

以聚乙烯醇、拜耳N3390、二甲基硅油、吸水树脂为原料,通过锐孔法成功制备了可降解聚氨酯微胶囊。以九水合硝酸铝、硝酸锶、硝酸铕(Ⅲ)六水合物、硝酸镝六水合物为原料,通过共沉淀法制备了[SrAl2O4（Eu2+, Dy3+, B）]黄绿色荧光粉。将实验制得的微胶囊,荧光粉与丙烯酸锌树脂按比例混合制备3种不同涂层：荧光粉防...     

N-(6-甲基-2-亚甲基吡啶)-(+)-樟脑亚胺体系的不对称烷基化反应

本文报道了手性酮亚胺中间体在LA作用下, 脱去质子形成碳负离子, 然后与各种卤代烷进行不对称烷基化反应。