Optimizing the efficiency of femtosecond-laser-written holograms

Computer-generated binary holograms are written on a polished copper surface using single 800-nm, 120-fs pulses from a 1-kHz-repetition-rate laser system. The hologram efficiency (i.e. the power in the holographic reconstructed image relative to the incoming laser power) is investigated for different laser-structuring parameters. Theoretical diffraction grating efficiencies for a binary amplitude grating show good agreement with the experimental measurements for diameters of the laser-formed holes below the pitch. Modelling based on straightforward geometrical arguments is used to find the optimal hole size. For a coverage (i.e. relative laser-structured area) of ～43 %, the efficiency reaches ～10 %, which corresponds to a relative power transferred to one reconstructed image of ～20 %. The efficiency as a function of pitch (for fixed coverage) is fairly constant from 2 to 6 μm.     

MEASUREMENT OF LOW MAGNETIC FIELD DISTRIBUTION OF A β SPECTROMETER

The low magnetic field distribution of an iron-core double-focusing low-energy β spectrometer is measured with a second harmonic magnetic flux gate magnetometer, the relative measuring precision is better than ±0.05%. The field strength of the spectrometer is about 10G. This spectrometer is used to measure the β spectrum from tritium β decay for estimating the rest mass of electron antineutrion.     

Crystal growth, spectroscopy, and diode pumped laser performance of Pr,?Mg:SrAl12O19

Polarization dependent ground state absorption, excited state absorption and emission cross sections of Pr,?Mg:SrAl₁₂O₁₉ are determined in the visible and ultraviolet spectral region. It is shown that excited state absorption to the 4f5d configuration does neither occur on the pump wavelength in the blue region nor on any of the visible laser transitions. Efficient laser action at 643.5?nm is demonstrated with slope efficiencies of up to 47% with respect to the absorbed pump power. Output powers up to 75?mW are achieved by pumping with an InGaN laser diode at 444?nm.     

Synthesis of crystalline Ge nanoclusters in PE-CVD-deposited SiO2 films

The synthesis of evenly distributed Ge nanoclusters in plasma-enhanced chemical-vapour-deposited (PE-CVD) SiO₂ thin films containing 8 at. % Ge is reported. This is of importance for the application of nanoclusters in semiconductor technology. The average diameter of the Ge nanoclusters can be controlled in the range of 3–6 nm by variation of the annealing parameters. Using a combination of transmission electron microscopy and Raman-scattering spectroscopy, the nanoclusters were shown to be crystalline. However, photoluminescence measurements showed no light emission that could be definitively correlated to the presence of the nanoclusters. PACS 61.82.Rx; 78.67.Bf; 81.07.Bc     

KDP晶体折射率非均匀性检测系统

基于正交偏振干涉法,建立了KDP晶体折射率非均匀性的检测系统,并可实现晶体相位失谐角的间接检测.波前检测系统实现了测试光偏振态的精密控制与切换,采用波长调谐相移的方法去除了测试过程中参考面倾斜引入的误差,优化了抗振动相移算法,提高了波前测试的测量准确度及重复性.通过折射率非均匀性分析算法的设计,解决了晶体厚度变化引入的误差等.小口径晶体元件的测试结果表明系统的折射率非均匀性检测准确度(均方根值)优于10~(-6).     

Comparison of models for predicting the transmission loss of plenum chambers

New experimental data for the transmission loss of plenum chambers are compared to results obtained using several different and well known prediction models. Results for transmission loss as a function of frequency in 1/3 octave bands are presented for a series of plenum chamber configurations of various sizes and interior acoustical treatments. In the experimental work the transmission loss was determined from simultaneous measurements at two upstream and two downstream microphones.     

基于顶空及表面增强拉曼散射(SERS)结合的葱属植物挥发性物质研究

为了在常温下鉴定新鲜植物样品的挥发性物质,且避免繁杂前期样品的制备过程,将新鲜样品切细后置入顶空瓶中,用注射器抽取顶空瓶上方的挥发性物质注入用微波法制备的纳米银溶胶中,用R-3000便携式拉曼光谱仪进行SERS的测量。获得了葱属植物大蒜、韭菜、葱的挥发性物质的表面增强拉曼光谱(SERS)。大蒜的SERS谱中较强的峰出现在307,399,569,711,1 182,1 287,1 397,1 622 cm-1处。韭菜的SERS谱中最强的峰出现在672 cm-1,较弱的峰出现在274,412,575,1 185,1 289,1 396,1 618 cm-1处。葱的SERS谱中最强的峰出现在693 cm-1,次强峰出现在372,888,1 023 cm-1处,较弱的峰出现在1 088,1 211,1 322 cm-1。获得二烯丙基二硫(diallyl disulfide)、烯丙基甲基硫醚(allylmethyl sulfide)、1-丙硫醇(1-Propanethiol)的液态、气态的SERS谱。经对比研究得出：吸附在银表面的大蒜、韭菜、葱的主要挥发性物质分别是二烯丙基二硫(diallyl disulfide)、烯丙基甲基硫醚(allyl methyl sulfide)、1-丙硫醇(1-Propanethiol)。同是葱属植物但不同种大蒜、韭菜、葱其吸附在银表面的主要的挥发性物质不一样,吸附在银表面的各种葱的主要挥发性物质都是1-丙硫醇。该实验结果表明顶空与SERS结合,不需要复杂的提取过程,可直接用于新鲜植物的挥发性物质快速检测。     

十六烷基氯化吡啶-水-KI体系浮选分离锑

研究了十六烷基氯化吡啶-水-KI体系分离Sb3+的行为及与一些金属离子分离的条件。结果表明,在一定条件下,Sb3+可与Co2+、Al3+、Zn2+、Ni2+、Fe2+和Mn2+定量分离。