Green Output of 1.5 W from a Diode-Pumped Intracavity Frequency-Doubled Self-Q-Switched and Mode-Locked Cr,Nd：YAG Laser

We report a diode-pumped intracavity frequency-doubled self-Q-switched and mode-locked Cr,Nd：YAG/KTP green laser with a Z-type cavity, which produces 1.5 W of average power at 532nm with incident pump power 14.2 W. The individual mode-locked green pulse duration is about 560ps with 149 MHz repetition rate. Almost 100% modulation depth of the mode-locked green pulses is achieved at an incident pump power of 4.13 W. The maximum energy of Q-switched green pulse is 19.8μJ. The experimental results of pulse duration and pulse energy of Q-switched green pulse agree well with the theoretical calculations.     

Surface oxidation of vanadium dioxide films prepared by radio frequency magnetron sputtering

This paper reports that the thermochromic vanadium dioxide films were deposited on various transparent substrates by radio frequency magnetron sputtering, and then aged under circumstance for years. Samples were characterized with several different techniques such as x-ray diffraction, x-ray photoelectron spectroscopy, and Raman, when they were fresh from sputter chamber and aged after years, respectively, in order to determine their structure and composition. It finds that a small amount of sodium occurred on the surface of vanadium dioxide films, which was probably due to sodium ion diffusion from soda-lime glass when sputtering was performed at high substrate temperature. It also finds that aging for years significantly affected the nonstoichiometry of vanadium dioxide films, thus inducing much change in Raman modes.     

PdYn±(n=0, 1, 2, 3)分子离子的结构与稳定性

在Pd和Y原子相对论有效原子实势和基函数SDD下, 使用密度泛函理论B3LYP方法对PdYn±(n=0, 1, 2, 3)分子离子的势能曲线与稳定性进行计算研究, 结果表明, PdY分子和PdY−, PdY2−, PdY3−与PdY+分子离子的基态电子状态分别为X2Σ、X1Σ、X2Σ、X1Σ、X1Σ, 能稳定存在, 势能函数可用Murrell-Sorbie函数表达, 并计算得到相应的力常数与光谱数据; PdY2+和PdY3+分子离子的基态分别为X2Σ和X1Σ, 是亚稳定态, PdY3+分子离子的三重态是排斥态, 不能稳定存在.     

钴分子筛催化剂的制备及其分子筛载体对环己烷氧化选择性的影响

为了考察催化剂载体的孔道结构和择形性能对环己烷部分氧化反应的影响,采用直接水热法制备出了Co/S-1,Co/TS-1以及Co/MCM-41分子筛催化剂.XRD,FT-IR和SEM结果表明合成的样品具有较高的结晶度,晶粒大小均匀,其活性组分钴进入了分子筛骨架.采用氧气为氧化剂,考察了合成的钴催化剂样品对环己烷部分氧化的催化性能,并与CoAPO-5、Co/A l2O3、均相Co(OAc)2.4H2O催化剂以及无催化氧化的结果进行了比较.实验结果表明:分子筛载体能利用其孔道结构和择形性能,降低环己醇(酮)选择性对环己烷转化率的依赖性,且反应的选择性随分子筛载体孔径的增加而下降.孔道较小的Co/TS-1和Co/S-1做催化剂时,过氧化物含量低,环己烷转化率可达5%以上,同时反应总选择性为95%左右.     

H12C14N分子v2垂直带的高温谱线强度及随温度的变化规律

采用乘积近似法计算了氰化氢分子H12C14N的总配分函数,其中转动配分函数考虑了离心扭曲修正,振动配分函数采用谐振子近似.利用计算所得配分函数和文献提供的实验振动跃迁矩平方及HermanWallis因子系数,计算了氰化氢分子H12C14Nv2垂直带,即0110-0000跃迁在常温和高温下的线强度,并与HITRAN数据库的数据进行了比较.结果显示,在296 K及温度高达3 000 K时,计算所得谱线强度与HI-TRAN数据库提供的结果均符合较好.表明对氰化氢分子H12C14N高温下的分子配分函数和线强度的计算是可靠的.进一步计算了0110-0000跃迁带在更高温度4 000和5 000 K的线强度及模拟光谱,并总结了该跃迁带中的谱线强度随温度的变化规律:对于转动量子数J≥32的跃迁谱线(包括P支、Q支和R支),当温度从296.K逐渐增加时,其线强度迅速增加,到1 000 K附近达到最大值,然后迅速减弱.对于转动量子数J<32的跃迁谱线(同样包括P支、Q支和R支),线强度在296 K时最大,然后随温度的升高迅速减弱.     

原子吸收光谱法测定铁路岩石边坡土壤中重金属含量

铁路岩石边坡土壤中重金属含量直接关系到铁路岩石边坡生态系统以及周边农田生态系统的环境安全。应用原子吸收光谱法检测了途经四川省紫色土丘陵区的成达铁路岩石边坡土壤与对照土壤中Pb, Cd, Zn, Cu, Mn等多种重金属元素的含量。结果表明：铁路岩石边坡土壤中重金属元素Pb和Mn的含量比对照土壤增加明显,增加幅度高达29.7%～35.4%;但重金属元素Cd, Zn, Cu在铁路岩石边坡土壤与对照土壤之间差别并不明显。     

Frequency doubled femtosecond Ti:sapphire laser with an assisted enhancement cavity

We report an enhancement cavity for femtosecond Ti:sapphire laser at the repetition rate of 170 MHz. An enhancement factor of 24 is obtained when the injecting pulses have an average power of 1 W and a pulse duration of 80 fs. By placing a BBO crystal at the focus of the cavity, we obtain a 392-m W intracavity doubled-frequency laser, corresponding to a conversion efficiency of 43%. The output power has a long-term stability with a root mean square(RMS) of 0.036%.     

Self-starting mode-locked picosecond Ti：sapphire laser by using of a fast SESAM

A stable continuous wave mode-locked picosecond Ti:sapphire laser by using a fast semiconductor saturable absorber mirror (SESAM) is demonstrated. The laser delivers pulse width of 20 ps at a central wavelength of 813 nm and a repetition rate of 100 MHz. The maximum output power is 1.34 W with pump power of 7 W which corresponds to an optical--optical conversion efficiency of 19.1%.     

Structural and optical properties of tungsten-doped vanadium dioxide films

Thin films of tungsten(W)-doped thermochromic vanadium dioxide(VO2) were deposited onto soda-lime glass and fused silica by radio frequency magnetron sputtering.The doped VO2 films were characterized by X-ray diffraction,optical transmittance measurement,and near field optical microscopy with Raman spectroscopy.X-ray diffraction patterns show that the(011) peak of W-doped thermochromic VO2 film shifts to a lower diffraction angle with the increase of W concentration.The optical measurements indicated that the transmittance change(△T) at wavelength of 2500 nm drops from 65%(T at 35℃ and 80℃ for undoped VO2 film) to 38%(T at 30℃ and 42℃ for the doped VO2 film).At the same time,phase transition temperature drops from 65℃ to room temperature or lower with the increase of W concentration.Near field optical microscopy image shows that the surface of W-doped VO2 film is smooth.Raman results show that the main Raman modes of W-doped VO2 are centered at 614 cm1,the same as that of undoped VO2,suggesting no Raman mode changes for lightly W-doped VO2 at room temperature,due to no phase transition appearing under this condition.     

IrB和IrB_2力学性质的第一性原理计算

采用平面波赝势密度泛函理论对0—100 GPa静水压下P1-IrB(空间群Pnma)和P5-IrB2(空间群Pmmn)结构的平衡态晶格常数、弹性常数等性质进行了研究.研究结果表明,P1-IrB不可压缩性随着压强的增加而增强;P5-IrB2结构在0—100 GPa范围内弹性常数、体弹模量、剪切模量均呈现出有规律的变化,当所加压强为50 GPa时,杨氏模量和在b方向的晶格常数发生异常变化.对零压下P1-IrB和P5-IrB2的电子结构的研究发现,二者均没有一个明显的带隙,主要原因为Ir原子和B原子间的共价作用.从P1-IrB和P5-IrB2的能带结构和态密度图可以发现这两种结构均有金属性.