Octagonal dual-concentric-core photonic crystal fiber for C-band dispersion compensation with low confinement loss

A novel kind of octagonal dual-concentric-core photonic crystal fiber （PCF） is calculated with the finite element method （FEM） and proposed for broadband compensation. In order to realize highly negative dispersion, the hole diameter of the second ring is reduced relative to conventional PCFs. Numerical simulation results show that when the diameters of large holes and small holes are 0.77 pm and 0.5 #m, respectively, and the pitch of the adjacent rings is 1.1 μm, the negative dispersion can achieve about 840 ps.nm^-1.km^-1 at 1 550 nm and the dispersion slope can match with single mode fiber （SMF-28） perfectly. This PCF can compensate the positive dispersion and also its slope of about 50 times its length of SMF-28 fiber, which is suitable for C-band optical fiber telecommunication as a dispersion compensation fiber.     

纳米氧化锡锑改性水性聚氨酯的制备与表征

以异佛尔酮二异氰酸酯(IPDI)、聚醚二醇（N-210）、二羟甲基丙酸（DMPA）、一缩二乙二醇（DEG）、三羟甲基丙烷（TMP）及纳米氧化锡锑（ATO）浆料为主要原料,制备了稳定的纳米ATO改性水性聚氨酯(APU)乳液。 粒径测试及透射电子显微镜（TEM）观察显示,纳米ATO在水性聚氨酯中分散较好,乳液粒径均小于100 nm; FTIR分析表明,纳米ATO粒子与水性聚氨酯(WPU)间可能存在化学键; 热重分析(TGA)测试显示,随纳米ATO添加量的增加,胶膜最大热分解温度逐渐提高,最大提高了约20 ℃;紫外-可见-近红外吸收及保温性能测试表明,随着纳米ATO添加量的提高,胶膜在800~2500 nm的透过率逐渐降低,但涂层在可见光区透过率均超过70%,热阻率由1.34×10-2 m2·℃/W提高至3.17×10-2 m2·℃/W。     

脉冲激光烧蚀块状靶材的双动态界面研究

给出脉冲激光作用块状靶材的烧蚀模型.根据能量平衡原理,导出烧蚀面的位置随时间的变化关系.利用绝热近似、温度连续性条件和能量平衡原理来获得烧蚀面与固液相界面边界条件.结合热传导方程,利用精确解与积分近似法相结合的方案,给出固液两相的温度分布与时间和位置的变化关系,以及固液相界面的位置随时间的变化规律,并与已有的理论和实验结果进行比较.最后以铝靶为例计算模拟了激光烧蚀的全过程计算. 关键词： 脉冲激光 等离子体 固液相界面 烧蚀面     

脉冲激光制备薄膜材料的烧蚀机理

研究了脉冲激光烧蚀靶材的整个过程.从包含热源项的导热方程出发，利用适当的动态边界条件，详细研究了靶材在熔融前后的温度分布规律，并且给出了熔融后的固、液分界面的变化规律.熔融后的温度演化规律和固液相界面均以解析表达式的形式给出.还根据能量平衡原理给出烧蚀面位置随时间的变化规律.以硅靶材为例计算模拟了激光烧蚀的整个过程，与实验结果符合较好. 关键词： 脉冲激光 烧蚀面 熔融 温度演化     

Banach空间中有限秩拟线性投影算子的逼近问题

证得:在Banach空间中,相对紧集上的恒等算子可由一列有限秩连续拟线性投影算子一致逼近.由此得到:线性算子为紧线性算子必须且仅须它可由一列有限秩连续齐性算子一致逼近.     

脉冲高能准分子激光烧蚀块靶产生等离子体的动力学过程的差分模拟

 利用质量连续性、动量守恒和能量守恒这三个基本方程,研究高能脉冲激光照射块状靶材产生等离子体的物理特性。采用差分法和Pichard迭代法,求解带特定边界条件的流体力学三方程,得出已喷射等离子体的温度、密度和速度的分布的迭代方程,并用计算机进行了数值模拟。     

Characteristics of Plasma Shock Waves Generated in the Pulsed Laser Ablation Process

We modify the Sedov theory to describe plasma shock waves generated in a pulsed laser ablating process,We also study the propagation characteristics of plasma shock during the preparation process of functional thin films deposited by a pulsed laser,In particular,we discuss in detail the temporal behaviour of energy causing the difference of the propagation characteristics between the plasma shock wave and the ideal shock wave in the point explosion model.Under the same experimental conditions,the theoretical results calculated with our modified Sedov theory are in good agreement with the existing experimental data.     

电磁学教学新模式的探索与实践

在电磁学教学实践的基础上,深入思考电磁学实验教学的三个不同层次,以及不同层次电磁学实验教学的重要作用,形成电磁学理论教学与三层次实验教学相结合的新教学模式,并在本校物理学院学生中实践,取得令人满意的效果.     

Effect of Pulse Width and Fluence of Femtosecond Laser on Electron--Phonon Relaxation Time

The electron phonon relaxation time as functions of pulse width and fluence of femtosecond laser is studied based on the two-temperature model. The two-temperature model is solved using a finite difference method for copper target. The temperature distribution of the electron and the lattice along with space and time for a certain laser fluence is presented. The time-dependence of lattice and electron temperature of the surface for different pulse width and different laser fluence are also performed, respectively. Moreover, the variation of heat-affected zone per pulse with laser Auence is obtained. The satisfactory agreement between our numerical results and experimental data indicates that the electron-phonon relaxation time is reasonably accurate with the influences of pulse width and Auence of femtosecond laser.     

PZT四方相区介电常数εr与晶格畸变关系的研究

从Haun的PZT热力学理论出发，给出了PZT四方相区介电常数ε_r与晶格畸变c/a关 系的基本方程，并深入地根据相关实验资料和物理图像的合理推论，建立了关于晶格畸变c/ a与介电常数ε_r相互依赖的基本关系式.然后，根据该基本关系式仔细地研究了PZT四 方相区晶格畸变c/a对介电常数ε_r影响的物理图像.与相关实验资料比较表明，基本 关系式得到的介电常数ε_r随晶格畸变c/a的变化规律,与相关实验结果相比较，两者 吻合得 关键词： 晶格畸变 r')" href="#">介电常数ε_r 四方相 PZT