Observation of enhanced two-photon absorption in ZnS quantum dots at an ultraviolet wavelength

Two-photon absorption(2PA) in zinc sulphide(ZnS) and Mn2+-doped ZnS quantum dots is reported by the z-scan technique,with nanosecond pulsed laser radiation at 355 nm.The observed values of the 2PA cross section of all the samples are 105 times larger than that of bulk ZnS.     

Effect of laser erosion on the copper and zinc concentrations in the surface layer of brass

A REMMA 102 scanning electron microscope equipped with semiconductor and wave spectrometers is applied to measure the copper and zinc concentrations in the surface layers of an M161 brass sample and the same sample subjected to a focused laser radiation. The results are compared with the results obtained with an MS3101 laser mass spectrometer having a laser-plasma ion source. The laser-assisted erosion of the surface layer in the brass is shown to significantly change the copper and zinc concentrations. It is found that, when the craters produced by laser pulses on the initial surface do not overlap, the copper and zinc contents in the laser-induced plasma correspond to their contents in the sample.     

Influence of laser radiation on the Mössbauer absorption spectra of CdS (Fe<Superscript>57</Superscript>) single crystal

Influence of laser radiation on the resonant absorption of gamma radiation from Fe⁵⁷ nuclei in cadmium sulphide is investigated. It is shown that under action of laser radiation the shape of the Mössbauer spectrum of the sample is modified. The observed modification of the spectrum is explained by the presence in the sample of acoustic vibrations arising as a result of photoacoustic effect.     

Radiation damage and decay characteristics of zinc selenide emission bands and their equivalence to zinc sulphide emission bands

Irradiation of zinc selenide at ～ 20°K with electrons capable of displacing zinc atoms results in the production of cathodoluminescence emission bands at 610 and 630 nm. Enhancement of the 630 nm emission band by electron damage requires the presence of copper in the samples. These emissions have been shown to give a peak energy shift to lower energies after excitation, as is characteristic of donor-acceptor pair recombination. It is concluded that the 610 and 630 nm emission bands of zinc selenide are equivalent to the self-activated and copper green emission bands of zinc sulphide. The 530 nm emission band of zinc selenide is not sensitive to electron damage, shows no time shift and is thought to be equivalent to the copper blue emission of zinc sulphide.     

稀土离子注入的ZnS各种颜色发光二极管

ZnS单晶注入一种或两种稀土离子来制备发光二极管。本文研究了发光亮度与注入剂量的关系,发光亮度与电流的关系和发光亮度与温度的关系等。同时记录了电致发光和阴极射线发射光谱。选取两种不同的稀土离子注入到同一晶面,由于它们的比例不同,发光颜色可从一种稀土离子单独发光的颜色连续地改变到另一种颜色。     

On the discovery of an unusual luminescent pigment in Van Gogh’s painting “Les bretonnes et le pardon de pont Aven”

Spectrally and lifetime-resolved UV-induced luminescence imaging have been applied to the in situ analysis of Vincent Van Gogh’s painting on paper “Les bretonnes et le pardon de pont Aven”. The in situ investigation revealed the presence of an unusual microsecond green emission from the white painted areas of the watercolour, and this long-lived emission has not been reported in modern paintings by other authors. In order to attribute and suggest an identification of the luminescent pigment, our analysis was integrated with further measurements on commercially available modern white pigments (zinc white, Lithopone white, Blanc Fixe, zinc sulphide, and copper-doped zinc sulphide) and with an in-depth study of the synthesis processes of zinc-based pigments available at the end of the 19th century. Analysis suggested an attribution of the unusual emission from the Van Gogh painting to a particular variety of zinc sulphide pigment, characterized by the presence of copper impurities which were unintentionally introduced in the crystal matrix during its production. The present study is the first application of lifetime imaging for the mapping of long-lived luminescence from the semi-conductor pigment.     

Spectra of Zn XIX and Zn XX in the 20–50 Å region

We have analyzed the spectra of highly ionized zinc and identified twenty four new lines of Zn XIX and Zn XX in the 20–50 Å region. The lines in this region are principally due to the transitions of the type 3snp, 3pnd, ns and 3dnf, np where $\text{n ? 4}$. The spectra were excited by laser irradiation of zinc in a vacuum and the lines have been identified by extrapolating the published data for isoelectronic ions.     

Production par evaporation sous vide de reseaux zones et lentilles

A simple evaporation technique for the production of unalterable Phase FZP and FZP arrays is described. The method is also usable for Fresnel lens making. Experimental results are given, and the characteristics are compared with those obtainable by zinc sulphide lens direct evaporation.     

Real-time monitoring of laser welding of galvanized high strength steel in lap joint configuration

Two different cases regarding the zinc coating at the lap joint faying surface are selected for studying the influence of zinc vapor on the keyhole dynamics of the weld pool and the final welding quality. One case has the zinc coating fully removed at the faying surface; while the other case retains the zinc coating on the faying surface. It is found that removal of the zinc coating at the faying surface produces a significantly better weld quality as exemplified by a lack of spatters whereas intense spatters are present when the zinc coating is present at the faying surface. Spectroscopy is used to detect the optical spectra emitted from a laser generated plasma plume during the laser welding of galvanized high strength DP980 steel in a lap-joint configuration. A correlation between the electron temperature and defects within the weld bead is identified by using the Boltzmann plot method. The laser weld pool keyhole dynamic behavior affected by a high-pressure zinc vapor generated at the faying surface of galvanized steel lap-joint is monitored in real-time by a high speed charge-coupled device (CCD) camera assisted with a green laser as an illumination source.     

The special features of the spectra of radical-recombination luminescence in ZnO and ZnS

The spectra of the radical-recombination luminescence (RRL) and photoluminescence of zinc oxide and zinc sulphide are studied. The appearance in the RRL spectra of new bands compared with those of photoluminescence is attributed to specific surface centers. The temperature dependence of RRL is explained on the basis of a change in the recombination mechanism of hydrogen atoms with temperature.     

New classification in the spectra of highly ionized Cu and Zn in the region below 55 Å

The extreme ultraviolet spectra of Cu and Zn are analyzed. New classifications in the wavelength region below 55 Å are tabulated. The spectra were excited by focussing high power laser radiation on plane targets in a vacuum. The spectral lines reported here correspond mainly to the transitions between levels of principal quantum number 3 and 4 in Cu XVI to XIX and Zn XVII to XX. The identifications are based on extrapolations of published data for isoelectronic ions.     

Effect of sintering aid (CdCl2) on the optical and structural properties of CdZnS screen-printed film

Sulphides of zinc and cadmium have been utilized effectively in various opto-electronic devices. In the present work cadmium zinc sulphide (Cd_0.4Zn_0.6S) thin film has been deposited on ultra clean glass substrate by a simple inexpensive screen-printing method using cadmium sulphide, zinc sulphide, anhydrous cadmium chloride and ethylene glycol. Cadmium chloride has been used as sintering aid and ethylene glycol as a binder. Effect of sintering aid on the optical and structural properties of prepared cadmium zinc sulphide film has been investigated. The optical band gap (E_g) of the film has been studied by using reflection spectra in wavelength range 325–600 nm. It is found that reflection spectra suffer a drastic fall at two places, which is indicative of two band gaps of film viz. 2.38 eV and 2.9 eV corresponding to CdS and Cd_0.6Zn_0.4S, respectively. This is suggestive of the fact that cadmium zinc sulphide is a wide band gap semiconducting material. X-ray diffraction also confirms the formation of Cd_0.6Zn_0.4S composition.     

双示踪元素X射线能谱诊断激光等离子体电子温度

在“星光Ⅱ”激光装置上对Mg/Al混合材料平面靶和Mg/Al示踪层金盘靶进行三倍频激光打靶实验,用平面晶体谱仪测量靶材料发射的X射线能谱,获取了示踪离子谱线实验数据.采用多组态Dirac-Fock方法计算所需原子参数,并在局域热动平衡条件下建立了双示踪离子谱线强度比随电子温度变化关系.在此基础上由双示踪元素等电子谱线法确定了Mg/Al混合材料平面靶及金盘靶激光等离子体的电子温度 关键词： 电子温度 激光等离子体 X射线能谱     

抗反射疏水红外窗口的制备研究

本研究利用纳秒激光两次双光束干涉无掩模烧蚀、快速制备硫化锌(ZnS)微纳结构抗反射疏水表面,使其红外透过率由原来的75%增加到92%,解决了表面淀积抗反射镀层膜层附着力、抗蚀性、热胀失配等问题.此方法加工过程快速简单,可实现大面积制作,且微纳结构使基底具有疏水性能,疏水角可达145fi.使其在光电子、太阳能、航空航天及红外制导等领域具有广泛的应用前景.     

等电子谱线法测量Mg/Al等离子体电子温度空间分布

 在“星光Ⅱ”激光装置上对Mg/Al混合材料埋点靶进行三倍频激光打靶实验,用空间分辨晶体谱仪测量靶材料发射的X光光谱,获取了示踪离子谱线实验数据。采用多组态Dirac-Fock方法计算所需原子参数,并在局域热动平衡条件下建立了双示踪离子谱线强度比随电子温度的变化关系。在此基础上由双示踪元素等电子谱线法确定了Mg/Al混合材料埋点靶激光等离子体电子温度空间分布。     

Near-field-enhanced,off-resonant laser sintering of semiconductor particles for additive manufacturing of dispersed Au–ZnO-micro/nano hybrid structures

Off-resonant near-field enhancement by gold nanoparticles adsorbed on crystalline zinc oxide significantly increases the energy efficiency of infrared laser sintering. In detail, ten different gold mass loads on zinc oxide were exposed to 1,064 nm cw-laser radiation. Variation of scan speed, laser power, and spot size showed that the energy threshold required for sintering decreases and sintering process window widens compared to laser sintering of pure zinc oxide powder. Transmission electron microscope analysis after focused ion beam cross sectioning of the sintered particles reveals that supported gold nanoparticles homogenously resolidify in the sintered semiconductor matrix. The enhanced sintering process with ligand-free gold nanoparticles gives access to metal–semiconductor hybrid materials with potential application in light harvesting or energy conversion.     

Equalization of the TE and TM complex eigenvalues of 90°-root-top reflectors and waxicons using thin-film dielectric coatings

The net TE (s) and TM (p) complex eigenvalues (reflection coefficients) of metallic 90°-roof-top reflectors and waxicons can be equalized by use of single thin-film dielectric coatings of appropriate thickness for each plane mirror of a roof-top or cone of a waxicon. This removes the anisotropy associated with these elements when used in laser resonators. Results are presented for devices that operate at 10.6 μm wavelength and that are made of a silver substrate coated with a zinc sulphide thin film. Deviations from the condition of equal complex eigenvalues caused by small film-thickness and angle-of incidence errors are also determined.     

Neutral particle emission from zinc oxide surface induced by high-density electronic excitation

Emission of neutral zinc and oxygen atoms and oxygen molecules emitted from zinc oxide surface by laser irradiation have been measured. It is found that the emission intensity starts to increase when the laser intensity exceeds a certain threshold value, indicating that the particle emission is a high density electronic excitation effect. The energy spectrum of emitted particles is found not to follow the Maxwellian distribution.     

Femtosecond laser writing of subwave one-dimensional quasiperiodic nanostructures on a titanium surface

One-dimensional quasiperiodic structures whose period is much smaller than the wavelength of exciting radiation have been obtained on a titanium surface under the multipulse action of linearly polarized femtosecond laser radiation with various surface energy densities. As the radiation energy density increases, the one-dimensional surface nanorelief oriented perpendicularly to the radiation polarization evolves from quasiperiodic ablation nanogrooves to regular lattices with subwave periods (100–400 nm). In contrast to the preceding works for various metals, the period of lattices for titanium decreases with increasing energy density. The formation of the indicated surface nanostructures is explained by the interference of the electric fields of incident laser radiation and a surface electromagnetic wave excited by this radiation, because the length of the surface electromagnetic wave for titanium with significant interband absorption decreases with an increase in the electron excitation of the material.     

The use of surface photovoltage measurements for the surface characterisation of photoconductors

Measurements of the surface photovoltage as a function of wavelength of the exciting radiation show a number of features which change with variations in the surface conditions. In the case of photoconducting cadmium sulphide, it is shown that the changing spectral features, rather than being directly associated with surface states, are due to bulk transitions which give rise to changes in the bulk carrier concentrations and (indirectly) to changes in the surface potential as a result of redistribution of charge between bulk and surface states.