Spectroscopic properties and radiative lifetimes of SiTe:A high-level multireference configuration interaction investigation

The 18 A-S states correlated to the lowest dissociation limit of SiTe were calculated by using a high-level multirefer-ence configuration interaction （MRCI） method, including scalar relativistic and spin-orbit coupling effects. Based on the calculated potential energy curves, the spectroscopic constants of bound states were determined, which are well consistent with previous experimental results. The spin-orbit matrix elements between the A-S states were computed, which lead to an in-deoth understanding, of oerturbations on the electronic state a^3∏. Finally. the transition dioole moments of allowed transitionsA^1∏-X^1∑^＋,E^1∑^＋-X^1∑^＋,a^3∏-d^3△,a^3∏-d^3△,a^∏-a′^3∑^＋,a^3∏-e^3∑^-,and the radiative lifetimes of A^1∏,E^1∑^＋,and a^3∏ were evaluated.     

基于近场激发与增强的新型多层纳米薄膜结构在非线性光学器件上的应用与发展前景

传统光学引入了远场衍射的尺度极限。自从提出了近场光学技术以来 ,由于近场扫描光学显微镜 (NSOM)系统的复杂性而使得近扬的引入和利用变得困难。具有多层纳米薄膜结构的超分辨近场结构 (Super RENS)的提出改变了这种局面 ,并在诸如超高密度光学数据存储、近场光刻技术、纳米光子学晶体管等领域获得了重要的应用。围绕Su per RENS技术 ,通过综述它的基本原理、物理机制以及各项应用 ,指出了基于近场激发与增强原理的新型多层纳米薄膜结构在未来非线性光学器件上的应用与发展前景     

LiF及AlF3对掺Tm3+氟磷玻璃光学、光谱性质、析晶性能及结构的影响

为了平衡掺铥氟磷玻璃对辐射寿命、发射截面和析晶稳定性的综合要求,研究了LiF及AlF₃对掺铥氟磷玻璃光学光谱性质和析晶性能的影响. 研究表明,高达30 mol%的LiF仍可保证氟磷玻璃具有较好的析晶稳定性能且其在提高Tm³⁺离子的辐射寿命上具有非常重要的作用;高AlF₃玻璃具有很好的析晶稳定性能,但Tm³⁺离子在其中的辐射寿命下降较快; 鉴于LiF和AlF₃含量的相对变化对发射截面的影响不大,因此 关键词： 氟磷玻璃 辐射寿命 发射截面 析晶稳定性     

Detection and jamming experiment of optical surveillance device in night equipment transportation北大核心CSCD

针对装备运输过程中可能遭遇侦拍的风险,结合运输安全需求,分析市面上常见的4类消费级侦拍装置(手机、卡片数码相机、单反相机和数码摄像机)的光电可探测性,并实现对各装置的有效干扰。通过搭建“猫眼”激光探测、激光干扰及回波信号接收系统,重点突破典型小口径侦拍装置的探测与识别,以及“猫眼”探测端与目标端的双向成像等理论和关键技术。在此基础上分析不同距离、干扰波长和孔径情况下可见光波段激光对“猫眼”目标的探测及成像干扰效果,并提出一种图像干扰效果评价标准及不同光学侦拍装置的有效干扰阈值。实验结果表明:典型光学侦拍装置在实验距离内具有良好的光电可探测性,并且可被有效干扰;在激光束完全覆盖镜头通光孔径时,目标与装置距离越近,激光束散角越小,波段越接近人眼敏感程度最大波段(555 nm),激光光束产生的非伤害性成像干扰效果越好。     

Growth, optical properties and laser performance of NdxLu1−xVO4 series crystals

Nd_xLu_1−xVO₄ (x = 0, 0.005, 0.02, 0.023, 0.03 and 0.05) series crystals have been grown by the Czochralski method. The results of X-ray powder diffraction experiments show that these crystals belong to the zircon-type structure. The cutoff wavelength of LuVO₄ is 330 nm and the transmittance is about 80% in 540-3010 nm. The functional relation of absorption coefficient α at 808 nm on Nd³⁺-doped concentration N_d in units of atomic % is obtained to be α = 7.649 N_d. The results of Judd-Ofelt analysis show that there is no obvious concentration quenching effect below 3 at.% doped concentrations. The highest output power at 1.06 μm is 1090 mW for Nd_0.02Lu_0.98VO₄ at the pumping power of 6.58 W of a laser diode, the optical-optical conversion efficiency is 16.6% and slope efficiency is 19.4%.     

数字微镜器件反射效率测试方法及装置北大核心CSCD

为了获得数字微镜器件的真实光学特性,提出了其反射特性测试方法,并搭建实验装置对数字微镜器件的相对反射效率进行了测试,搭建了测试光路;利用该光路分别测得数字微镜器件和铝反射镜作为反射元件时相机接收到的光斑能量分布曲线,并对曲线进行积分;将2种测试条件下获得的积分值做除法,得到数字微镜器件的相对反射效率。测试结果表明,在使用632.8 nm波长激光器作为光源时数字微镜器件的相对反射效率为45.33%,在使用白光LED作为光源时数字微镜器件的相对反射效率为71.75%,经过多次测试发现2种测试模式下的重复精度均为±5%左右。上述测试结果可对今后使用数字微镜器件开发相关仪器时的能量传递效率计算以及器件选择起到一定参考作用。     

First-principles calculations for electronic, optical and thermodynamic properties of ZnS

The electronic, optical and thermodynamic properties of ZnS in the zinc-blende （ZB） and wurtzite （WZ） structures are investigated by using the plane-wave pseudopotential density functional theory （DFT）. The results obtained are consistent with other theoretical results and the available experimental data. When the pressures are above 20.5 and 27 GPa, the ZB-ZnS and the WZ-ZnS are converted into indirect gap semiconductors, respectively. The critical point structure of the frequency-dependent complex dielectric function is investigated and analysed to identify the optical transitions. Moreover, the values of heat capacity Cv and Debye temperature θ at different pressures and different temperatures are also obtained successfully.     

Structural, optical and electrical properties of ZnO:Al thin films for optoelectronic applications

Undoped and aluminum-doped ZnO thin films are prepared by the sol–gel spin-coating process. Zinc acetate dihydrate, ethanol and mono-ethanolamine are used as precursor, solvent and stabilizer, respectively. The atomic percentage of dopant in solution were [Al/Zn] = 1 %, 2 % and 3 %. The effect of Al doping on the optical and electrical properties of ZnO films was investigated by X-ray diffraction (XRD), Four-Point probe technique and UV–visible spectrophotometery. The results from the X-ray diffraction show that the pure ZnO thin films had a polycrystalline structure of the hexagonal Wurtzite Type. A minimum resistivity of $3.3 \times 10^{-3} \Omega \cdot \mathrm{cm}$ was obtained for the film doped with 2 mol % Al. Optical transmissions reveal a good transmittance within the visible wavelength spectrum region for all of the films. The value of the band gap is enhanced from 3.21 eV (undoped ZnO) to 3.273 eV (Al/Zn = 3 %), the increase in the band gap can be explained by the Burstein–Moss effect.     

Synthesis,optical, dielectric,thermal and mechanical properties of a nonlinear optical amino acid crystal: Bis-glycine hydrobromide

A semi organic material Bis-glycine hydrobromide (C₄H₁₁N₂O₄⁺Br⁻) has been synthesized by slow solvent evaporation technique. The grown crystal was subjected to single crystal X-ray diffraction studies and its crystal parameters were confirmed. The FTIR analysis confirms the presence of various functional groups present in the title compound. The Kurtz powder second harmonic generation test shows that the crystal is a potential candidate for optical second harmonic generation. The UV–vis spectrum reveals the transparency of the crystal and enumerates the direct band gap energy of the material. The dielectric constant and the dielectric loss were studied as a function of frequency. The thermal studies indicate that the material is thermally stable up to 290 °C. The hardness number was calculated to be 110 kg/mm² from the Vicker's microhardness test.     

Structural,electronic, and optical properties of ZnO:ZnSnN2 compounds for optoelectronics and photocatalyst applications

Semiconductors with suitable band gap are highly desirable for the applications in optoelectronic and energy conversion devices. In this work, using the recently developed strongly constrained and appropriately normed (SCAN) density functional calculations in conjunction with hybrid functional, we investigate the structural, electronic, and optical properties of earth abundant element based ZnO:ZnSnN₂ compounds formed through alloying. The proposed ZnO:ZnSnN₂ compounds in the low energy configurations possess band gaps of 2.28 eV-2.52 eV. The decrease in band gap compared to ZnO is mainly attributed to the p-d repulsion between N 2p+O 2p and Zn 3d electrons that lifts the top of valence band. For the ZnO:ZnSnN₂ compounds studied the band edges straddle the water redox potentials and the absorption onsets lie in the visible light range. Our studies are helpful for ZnO:ZnSnN₂ compounds' experimental synthesis and future application in optoelectronics and photocatalyst.     

水分子高激发态的绝热势能面与光解机制

本文在从头算icMRCI+Q水平上,发展了水分子的基态和九个激发态?、?、B、C、D、D''、D''、?''和F的全维绝热势能面. 势能面的拟合采用了高斯过程回归并结合置换不变多项式方法. 通过选择大的活动空间与添加额外弥散函数的基组来准确描述这些里德堡状态,计算得到的垂直激发能和平衡构型与先前的理论与实验值十分吻合. 相对于前三个被广泛研究的低能量电子态,对高激发态光解的理论与实验研究仍然十分有限. 本文研究了水在真空紫外光解过程中涉及到的高激发态的全部三个解离通道. 特别是基于新发展的势能面,首次清晰地阐明了D-E''、E''-F、?-?和?-C电子态之间的锥形交叉等信息,文中详细讨论了这些电子激发态的非绝热解离途径,为阐明这些高里德堡态的光解离机制提供了帮助.     

Synthesis, characterization and optical properties of water-soluble ZnS:Mn nanoparticles

ZnS nanoparticles with Mn²⁺ doping (0.5-20%) have been prepared through a simple chemical method, namely the chemical precipitation method. The structure of the nanoparticles has been analyzed using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and UV-vis spectrometer. The size of the particles is found to be 3-5 nm range. Photoluminescence spectra were recorded for undoped ZnS nanoparticles using an excitation wavelength of 320 nm, exhibiting an emission peak centered at around 445 nm. However, from the Mn²⁺-doped samples, a yellow-orange emission from the Mn²⁺⁴T₁-⁶A₁ transition is observed along with the blue emission. The prepared Mn²⁺-doped sample shows efficient emission of yellow-orange light with the peak emission 580 nm with the blue emission suppressed. The maximum PL intensity is observed only at the excitation energy of 3.88 eV (320 nm). Increase in stabilizing time up to 48 h in de-ionized water yields the enhancement of emission intensity of doped (4% Mn²⁺) ZnS. The correlation made through the concentration of Mn²⁺ versus PL intensity resulted in opposite trend (mirror image) of blue and yellow emissions.     

Synthesis,growth and optical properties of semi organic non linear optical single crystal: l-Arginine acetate

In the recent past, nonlinear optical materials are getting attention in the field fibre optic communication and optical signal processing. In the present study, the title compound was successfully synthesized by conventional chemical reaction and then the single crystal was grown by slow evaporation solution growth technique. l-Arginine acetate (LAA) is semi organic non linear optical single crystal and crystallizes in noncentrosymmetric space group. The grown good quality single crystals have been analyzed by different characterization analyses such as powder X-ray diffraction, high resolution X-ray diffraction (HRXRD), Raman spectroscopy, photoluminescence, SEM, micro-hardness, thermal and birefringence analyses.     

Synthesis of Pr-doped ZnO nanoparticles: Their structural,optical, and photocatalytic properties

Undoped and praseodymium-doped zinc oxide(Pr-doped ZnO)(with 2.0-mol%–6.0-mol% Pr) nanoparticles as sunlight-driven photocatalysts are synthesized by means of co-precipitation with nitrates followed by thermal annealing.The structure, morphology, and chemical bonding of the photocatalysts are studied by x-ray diffraction(XRD), scanning electron microscopy(SEM) with energy dispersive x-ray emission spectroscopy(EDS), x-ray photoelectron spectroscopy(XPS), and Fourier transform infrared spectroscopy(FTIR), respectively. The optical properties are studied by photoluminescence(PL) and UV-vis diffuse reflectance spectroscopy(UV-vis DRS). We find that Pr doping does not change the crystallinity of ZnO; but it reduces the bandgap slightly, and restrains the recombination of the photogenerated electron–hole pairs. The photocatalytic performance of the photocatalysts is investigated by the photodegradation reaction of 10-mg/L rhodamine B(RhB) solution under simulated sunlight irradiation, showing a degradation rate of 93.75% in ZnO doped with6.0-mol% Pr.     

Structural,electronic, optical and bonding properties of strontianite,SrCO3: First-principles calculations

The first-principles calculations are performed within the density functional theory to investigate the crystal structure, energy band structure, density of states, optical properties, and bonding properties of strontianite. The optimized structure parameters and bonding results with the generalized gradient approximation (GGA) functional and the localized density approximation (LDA) functional are in good agreement with the earlier experimental data. The band structure, density of states and chemical bonding of strontianite have been calculated and analyzed. The indirect band gap of strontianite is estimated to be ~4.45 eV (GGA) or ~4.24 eV (LDA). The absorption, reflectivity, refractive index and extinction coefficient have been calculated using the imaginary part of the dielectric function. The calculated results of the optical properties show that strontianite has an optical anisotropy along [100] (or [010]) and [010] polarization directions of incoming light. Furthermore, the calculated results of the density of states and Mulliken population indicate that the interactions among atoms are both ionic and covalent bonding in strontianite.     

Up-conversion and optical storage properties of SrS: Eu, Sm in PMMA

An erasable and rewritable optical-storage material SrS: Eu,Sm synthesized. Optical emission and excitation spectra of this material were measured. Using the SrS: Eu, Sm-PMMA film, the image-recording experiment was performed.     

Structural,electronic, and optical properties of oligoquinolines for light‐emitting diodes

The purpose of this work is to provide an in‐depth investigation of the electronic and optical properties of a series of n‐type conjugated oligomers, including 4‐phenyl‐6‐(4‐phenylquinolin‐6‐yl)quinoline (B1), 6,6′‐bis(2,4‐diphenylquinoline) (B1PPQ), 6,6′‐bis(2‐(4‐tert‐butylphenyl)‐4‐phenylquinoline) (BtBPQ), 6,6′‐bis(2‐p‐biphenyl)‐4‐phenylquinoline) (B2PPQ), and 4‐(6‐(2‐(4‐aminophenyl)‐4‐phenylquinolin‐6‐yl)‐4‐phenylquinolin‐2‐yl)benzenamine (BNPPQ). The geometric and electronic structures of the oligomers in the ground state were investigated using density functional theory (DFT) and the ab initio HF, whereas the lowest singlet excited states were optimized with ab initio CIS. To assign the absorption and emission peaks observed in the experiment, we computed the energies of the lowest singlet excited states with time‐dependent (TD) DFT (TD‐DFT). All DFT calculations were performed using the B3LYP functional and the 6‐31G basis set. The results show that the HOMOs, LUMOs, energies gaps, ionization potentials and electron affinities for each molecular are significantly affected by varying the aryl substituents, which favor the hole injection into OLEDs. The absorption and emission spectra exhibit red shifts to some extent [the absorption spectra: 335.85 (B1)< 370.63 (B1PPQ) < 376.77 (BtBPQ)< 388.67 (B2PPQ)< 412.93 nm (BNPPQ); the emission spectra: 391.48 (B1)< 430.11 (B1PPQ)< 435.86 (BtBPQ)< 444.57 (B2PPQ)< 463.28nm (BNPPQ)]. The radiative lifetimes (τ) of each oligomers are calculated as well. Because of introducing the cooperation with the electron donators such as the amidocyanogen in the common 4‐phenyl‐6‐(4‐phenylquinolin‐6‐yl)quinoline core for BNPPQ, which results in improving the hole‐creating ability. Copyright © 2008 John Wiley & Sons, Ltd.     

Strain-tunable electronic,elastic, and optical properties of CaI2 monolayer: first-principles study

ABSTRACT

The effects of biaxial strain on the electronic structure and the elastic and optical properties of monolayer CaI₂ were studied using first-principles calculations. The two-dimensional (2D) equation of state for monolayer CaI₂ as fit in a relative area of 80–120% is more accurate. The band gap can be tuned under strain and reached a maximum at a tensile strain of 4%. Under compressive strains, the absorption spectrum showed a significant red shift at higher strains. The static reflectance and static refractive index decreased in the strain range of ?10% to 10%.