Room-temperature cw and pulsed operation of a diode-end-pumped Tm:YAP laser

We report the continuous-wave and acousto-optical Q-switched operation of a diode-end-pumped Tm:YAP laser. Continuous-wave output power of 3.5 W at 1.99 μm was obtained under the absorbed pump power of 14 W. Under Q-switched laser operation, the average output power increased from 1.57 W to 2.0 W, with an absorbed pump power of 12.6 W, as the repetition rate increased from 1 kHz to 10 kHz. The maximum Q-switched pulse energy was 1.57 mJ with a repetition rate of 1 kHz. The minimum pulse width was measured to be about 80 ns, corresponding to a peak power of 19.6 kW. PACS 42.55.Rz; 42.55.Xi; 42.60.Gd     

曲率半径误差对平场全息凹面光栅分辨率的影响及其补偿方法

在平场凹面全息光栅的没计制作中,不可避免的存在曲率半径误差,严重影响光栅光谱仪的分辨率.为了从理论上分析并指导光谱仪器的设计和装调,运用几何光线追迹方法计算并分析了不同曲率半径误差下光谱像宽度的变化规律,发现在一个较大的误差范围内子午焦线的位置随着曲率半径的变化前后平移,同时其弯曲程度几乎没有改变.数值计算发现通过调整像面位置或人臂长度均能够补偿曲率半径的误差.数值模拟结果显示,修正使用结构后的光栅能够达到与设计结果相近的成像质量.     

Ultraviolet band edge photorefractivity in LiNbO3:Sn crystals

The ultraviolet (UV) band edge photorefractivity of Sn-doped LiNbO(3) (LN:Sn) at 325 nm has been investigated. A sharp decrease of beam distortion, which is accompanied by a significant increase in the photoconductivity, is observed in LN:Sn crystals with Sn-doping concentrations at or above 2.0 mol%. The diffraction efficiency, the holographic recording sensitivity and response rate, and the two-wave coupling gain coefficient are greatly enhanced when the Sn-doping concentration reaches 2.0 mol% or more. Unlike LiNbO(3) doped with Hf in which the UV gratings can be erased easily by a red beam, the UV gratings in LN:Sn can withstand long-term red beam illumination. Electrons are determined to be the dominant light-induced charge carriers responsible for the UV band edge photorefraction. The observed enhancement on the UV band edge photorefractivity is found to be associated with the showup of an absorption band around 325 nm in LN:Sn crystals with Sn-doping concentrations at or above 2.0 mol%.     

Multiple-trap laser tweezers Raman spectroscopy for simultaneous monitoring of the biological dynamics of multiple individual cells

We report the development of a multiple-trap laser tweezers Raman spectroscopy (LTRS) array for simultaneously acquiring Raman spectra of individual cells in physiological environments. This LTRS-array technique was also combined with phase contrast and fluorescence microscopy, allowing measurement of Raman spectra, refractility, and fluorescence images of individual cells with a temporal resolution of ~5 s. As a demonstration, we used this technique to monitor multiple Bacillus cereus spores germinating in a nutrient medium for up to 90min and observed the kinetics of dipicolinic acid release and uptake of nucleic acid-binding stain molecules during spore germination.     

Multiple Čerenkov second-harmonic waves in a two-dimensional nonlinear photonic structure

We report simultaneous generation of multiple conical second-harmonic waves in a two-dimensional nonlinear photonic structure when illuminated by two overlapping noncollinear fundamental beams. We show that this phenomenon is caused by the nonlinear ?erenkov radiation emitted due to the interaction of photons from each constituent fundamental beam as well as the virtual one propagating along the bisector of the two beams. In addition, by studying the asymmetric geometry of the interaction, we uniquely verify the effects of reciprocal vectors on the ?erenkov-type second-harmonic generation in nonlinear photonic structures.     

Superexchange interaction enhancement of the quantum transport in a DNA-type molecule

We use the transfer matrix method and the Green function technique to theoretically study the quantum tunnelling through a DNA-type molecule. Ferromagnetic electrodes are used to produce the spin-polarized transmission probability and therefore the spin current. The distance-dependent crossover comes from the topological variation from the one-dimensional to the two-dimensional model transform as we switch on the interstrand coupling; a new base pair will present N-1 extrachannels for the charge and spin as N being the total base pairs. This will restrain the decay of the transmission and improve the stability of the quantum transport. The spin and charge transfer through the DNA-type molecule is consistent with the quantum tunneling barrier.     

束缚定态径向Schrödinger方程的节点解法

本文介绍了束缚定态径向Schrödinger方程的节点解法^[1,2]。详细分析了其理论的依据,给出了实施步骤和注意事项。文末还附了二个计算实例。和其它方法相比,本解法占用内存少,运算速度快而且计算精度高。可在内存256K,字长16位的PC机上实现。     

Local spatial transformations and local observables

Traditionally spatial transformations such as translations and rotations are formulated in terms of transformations of the entire spatial space. In other words, transformations are taken automatically to be of a global nature. This paper investigates a local approach to spatial transformations; local transformations lead naturally to local observables in quantum mechanics.     

R_2Fe_17_C化合物的结构与内禀磁性的研究

本文系统研究了R_2Fe_17_C(R=Y,Sm,Gd,Tb、Dy.Er) 化合物的结构与内享磁性, 井与相应的R_2Fe_17_C 化合物进行了比较.R_2Fe_17_C 的居里温度比相应氏R_2Fe_17 的居里温度增加大约200K. 本文讨论了C 原子对该化合物结构与磁性的影响, 同时, 还对Sm_2(Fe_1-xCo_x)_17C系列化合物进行了研充. 关键词：     

OSCILLATION OF A FORCED SECOND ORDER NONLINEAR EQUATION

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