一维光子晶体微腔在硅基材料发光中的应用研究

硅基材料的高效发光对未来硅基光电子集成的发展极其关键,含微腔的一维光子晶体可以显著提高其发光强度、窄化其发光峰.介绍了几种硅基材料发光的一维光子晶体微腔结构,包括单缺陷模式的对称与非对称结构、多缺陷模结构及电注入结构.利用传输矩阵法计算其缺陷模透射谱,以间接分析其发光谱.     

偶氮苯聚合物全息光栅衍射效率和偏振特性研究

研究了不同偏振全息模式下基于交联偶氮苯聚合物薄膜的相位光栅的形成机理、衍射效率和偏振特性.利用琼斯矢量表征了正交线偏振(SP)和半行线偏振(SS)干涉模式下的偏振干涉场.基于SP和SS两种模式,制作了无明显表成起伏的纯折射率光栅和有表面起伏的浮雕光栅.偏光显微镜(POM)观测说明纯折射率光栅具有周期性的折射率分布;近场光学显微镜(SNOM)探测说明纯折射率光栅和浮雕光栅的表而起伏在5 nm以下和 85.23 nm.实验表明.当探测光为水平偏振时,纯折射率光栅的衍射效率达到22.2%.浮雕光栅只能达到1.65%.纯折射率光栅的0、 1级衍射光分别为水平和竖直线偏振光,偏振度达到0.9969和0.9963;浮雕光栅的0, 1级衍射光均为水平线偏振光.     

蓝宝石晶体的光谱精细结构、零场分裂参量及晶体结构

运用不可约张量算法和群理论构造了C3v对称晶场中3d5组念离子的252阶可完全对角化的微扰哈密顿矩阵.用此矩阵计算了Al2O3:Fe3 晶体的光谱精细结构、零场分裂参量(D,a-F)、品体结构,其理论计算值与实验值相符合,并研究了自旋四重态、自旋二重态分别对基态能级的影响,证明了自旋四重态对基态能级的贡献是主要的,自旋二重态对基态能级的贡献虽很小,但却是不可忽略的.进一步研究了SO梢合作用、SS耦合作用对Al2O3:Fe3-品体的光谱精细结构和零场分裂参量的影响,结果发现SO耦合作用是最主要的,SS耦合作用也是不可忽略的.     

Preparation of hard magnetic materials in thin film form

We report on the preparation, by means of pulsed laser ablation deposition, of trilayers of nominal composition Cr/SmCo₅/Cr//Si with thicknesses in the order of 250/240/125 nm, respectively. According to the results of the structural, chemical and magnetic characterizations performed in our as-deposited samples, the Sm–Co layer was structurally amorphous, exhibited abrupt compositional interfaces with the capping and buffering layers, and coercivities of a few hundreds of Oe. Magnetic hardness was developed upon submitting the samples to current anneals under vacuum at temperatures in the range of 540–670 °C. The hardening process was followed in detail by correlating the phase distribution, the nature of the interlayer atomic diffusion processes, the occurrence of textures and the temperature dependence of the coercive force. From our results we conclude about (i) the occurrence of a large degree of Co diffusion/segregation, which results in the detection, from the diffraction and magnetometric results, of the presence of CoCr alloys in the treated samples, and (ii) the close correlation, evidenced from the fits of the temperature dependence of the coercive force to the micromagnetic model, between the coercivity optimization and the crystallinity enhancement of the SmCo₅ grains.     

Annealing dependence of magnetic properties in nanostructured Sm0.5Y0.5Co5

Nanocrystalline Sm_0.5Y_0.5Co₅ powders with high coercivity H_C and enhanced remanence M_r were prepared by mechanical milling and subsequent annealing. Annealing temperatures T ranging from 973 to 1173 K, and times t ranging from 1 to 5 min were used. X-ray diffraction (XRD) and DC-magnetization measurements were carried out to study the microstructure and magnetic properties of these samples. XRD patterns demonstrate that the average grain size D of the nanocrystalline powders depends on the annealing temperature T and time t: D ranges from 11 nm (for T=973 K and t=1 min) to 93 nm (for T=1173 K and t=5 min). Magnetic measurements performed at room temperature indicate high coercivity values (H_C>955 kA/m), and enhanced remanence (M_r/M_max>0.5) for all samples. A strong annealing-induced grain size dependence of these magnetic properties was found.     

Magnetic properties of YCo5 (70%wt)+Y2Co17 (30%wt) nanocomposite powders at low temperatures

Nanostructured YCo₅ (70%wt)+Y₂Co₁₇ (30%wt) composite powders were prepared by mechanical milling and subsequent annealing at 1073 K for 1.5 min. The average grain size D of the YCo₅ and Y₂Co₁₇ phases, obtained from XRD data, was 14 and 12 nm, respectively. The temperature dependence of the magnetic properties was studied by DC magnetization measurements at temperatures T ranging from 3 to 300 K. Hysteresis loops (H_max=70 kOe) show that both the coercivity H_C and the squareness σ_r/σ_max are temperature-dependent. The coercivity increases from 12 kOe at room temperature to 18 kOe at T=3 K. The observed enhanced remanence (σ_r/σ_max>0.5) indicates that a strong exchange coupling is present at all temperatures used in this study. The maximum magnetization σ_max changes little with temperature and has a value of about 70% of the effective saturation magnetization of the title compound.     

电磁波在左右手介质界面折射与反射特性的研究

研究了电磁波在左右手介质界面折射与反射的特性,给出了折射系数和反射系数,从另外一个方面探讨了最小作用量原理在左手材料中的适用性;从电动力学和最小作用量原理证明了Snell定律,验证了Snell定律在左手材料中的适用性,并且得到Fresnell公式在左右手材料中的一致性.     

超声波对合成介孔材料Al-MCM-41的有序度的影响

在超声频率为20 kHz,电功率为500 W的超声波作用下,分别以Al（NO₃）₃和Al₂ （SO₄）₃做铝源合成了具有不同Si/Al比的Al-MCM-41。XRD结果显示,尽管超声波作用下,掺杂杂原子Al也要降低介孔材料的有序度,但其有序度降低的程度比普通水热法要小,超声波的辅助可以在同样反应时间内得到比普通水热法具有更高有序度的Al-MCM-41,即在掺杂过程中,超声波要比普通搅拌有利于介孔材料保持其骨架稳定性。此外考察了超声波作用时间对产品有序度和粒度的影响。     

平面和曲面光学零件气囊抛光材料去除的比较研究

气囊数控抛光是近年来一种新兴的先进光学制造技术,采用柔性的气囊作为抛光工具并以进动的方式进行加工。首先简要阐述了气囊抛光的抛光原理,然后针对平面和曲面光学零件,在自行研制的气囊抛光实验样机上进行了抛光实验。被抛光光学元件的材料去除是在抛光区内实现的。研究了进动角、气囊压缩量、气囊内部压力、气囊转速、抛光时间以及工件的曲率半径几种重要的工艺参数对平面工件和球面工件抛光接触区大小和形状影响情况的异同。在此基础上,总结了气囊抛光材料去除的影响规律。给出了几种重要工艺参数在平面工件和球面工件上取值范围。     

透极远红外光学材料制备及性能研究

在一定的温度、压力等条件下,采用有机材料(聚四氟乙烯)和无机晶体(KBr、CsI),通过热合技术研制出样品几何尺寸为Φ20mm×3-5mm、透射波段分别为15-38μm(PE-KBr)和15-60μm(PE-CsI)的透极远红外复合光学材料。抗腐蚀性能测试结果表明,材料耐强酸、强碱及部分有机溶剂。机械性能分析表明材料在小于115℃范围内可安全使用。极远红外透过率测试结果表明,在1-15μm波段,平均透过率小于15%,15-38μm和15-60μm极远红外波段,平均透过率大于50%,并对影响材料透过率的因素进行了分析。