金属超微粒子-半导体薄膜的光学瞬态响应

利用飞秒脉冲激光和泵浦 探测技术测量了金属超微粒子 半导体复合薄膜Ａｇ-ＢａＯ的瞬态光学透过率随延迟时间的变化曲线，观察到了薄膜对光的吸收漂白现象，并在不到２ｐｓ时间内恢复．该现象是薄膜中金属超微粒子内费密能级附近电子被飞秒激光脉冲激发，产生非平衡电子而经历瞬态弛豫造成的．弛豫主要包括非平衡电子越过超微粒子和周围介质的界面位垒进入周围介质，以及非平衡电子同晶格和界面的散射两种过程．超微粒子粒径的差别会引起非平衡电子弛豫时间的差别 关键词：     

金属超微粒子─半导体薄膜的光学瞬态响应

利用飞秒脉冲激光和泵浦探测技术测量了金属超微粒子半导体复合薄膜ＡｇＢａＯ的瞬态光学透过率随延迟时间的变化曲线，观察到了薄膜对光的吸收漂白现象，并在不到２ｐｓ时间内恢复．该现象是薄膜中金属超微粒子内费密能级附近电子被飞秒激光脉冲激发，产生非平衡电子而经历瞬态弛豫造成的．弛豫主要包括非平衡电子越过超微粒子和周围介质的界面位垒进入周围介质，以及非平衡电子同晶格和界面的散射两种过程．超微粒子粒径的差别会引起非平衡电子弛豫时间的差别     

常态下Pr掺杂Y—Ba—Cu—O薄膜的激光响应研究

本文对倾斜基片上生长的ＹＢａＣｕＯ薄膜在不同膜厚和多种浓度Ｐｒ掺杂条件下的激光响应进行了研究．这种现象的根源是薄膜层状结构造成的热电系数张量各向异性．与未掺杂ＹＢａＣｕＯ薄膜的激光响应相比，掺Ｐｒ使薄膜的激光响应幅度显著提高，并且仍具有较好的能量线性响应和时间响应．掺Ｐｒ２０％，效应最明显；掺Ｐｒ５０％时，效应则显著降低．本文认为，由于Ｐｒ掺杂使ＣｕＯ面载流子浓度降低从而显著增强声子曳引作用是导致ＹＢａＣｕＯ薄膜ＣｕＯ面热电系数增大及其激光响应幅度提高的主要原因     

YBa2Cu3O7—δ中Cu—O伸缩振动的红外吸收峰

测量了ｃ轴高度定向的ＹＢａ２Ｃｕ３Ｏ７－δ高Ｔｃ超导薄膜经３００～７５０℃退火后的红外反射光谱和不同掺Ｚｎ量的ＹＢａ２Ｃｕ３－ｘＺｎｘＯ７－δ块状材料的红外吸收光谱。根据这些光谱中Ｃｕ－Ｏ吸收峰的变化，证实了在ＹＢａ２Ｃｕ３Ｏ７－δ体系的红外光谱中，６３０ｃｍ＾－１、５９０ｃｍ＾－１、和５５０ｃｍ＾－１三个吸收峰分别对应的Ｃｕ－Ｏ伸缩振动膜，以及与氧缺位的关系。并讨论了二维电子气屏蔽对吸收峰的影响     

基于飞秒瞬态反射/透射技术的纳米Au半透膜热效应研究

以飞秒激光放大器作为光源联合使用瞬态反射/透射实验技术研究了纳米Au半透明纳米薄膜中非平衡载能粒子的热传导过程. 在相同实验条件下, 发现该薄膜的瞬态透射和反射信号明显不同并且延迟时间在5.0–7.5 ps时瞬态透射信号的符号发生改变. 对纳米薄膜的透射和反射信号进行了对比分析, 分别使用双温模型和Crude近似进行数据模拟并拟合, 分析认为沿膜厚方向的温度梯度变化和界面热阻效应引起介电函数的变化不同, 从而引起了瞬态透射信号和反射信号的不同. 对于半透明金属纳米薄膜需要同时考虑其瞬态透射和反射影响才能得到准确的瞬态吸收结果. 随着抽运脉冲能量的增加, 可以看到上升时间约为1.0 ps, 电子-晶格弛豫时间增加.     

在金属基片上激光沉积YBCO超导薄膜

介绍了在金属基片上激光沉积缓冲层和ＹＢａ２Ｃｕ３ｏ７－ｘ（ＹＢＣＯ）高温超导薄膜的研究结果。在带ｙｔｔｒｉａ－ｓｔａｂｉｌｉｚｅｄ－ｚｉｒｃｏｎｉａ（ＹＳＺ）缓冲层的ＮｉＣｒ合金基片上,激光原位沉积出ＹＢＣＯ超导薄膜,薄膜的零电阻转变温度度４８Ｋ,７７Ｋ时临界电流密度约为２００Ａ／ｃｍ＾２;缓冲层的取向可以通过选择适当的沉积参数来改善;用扫描隧道电子显微镜对ＹＢＣＯ薄膜的微观结构分析表明：完善的螺     

飞秒脉冲激光加热金属薄膜的理论和实验研究

超短脉冲激光加热可应用于研究材料中载能子之间的超快相互作用,同时也广泛应用于超快激光加工.此前人们提出的双温度模型和抛物一步模型都只能用于描述超短脉冲激光加热金属薄膜后热量传递过程的特定片段.基于双温度模型和傅里叶导热定律,提出普适的理论模型可用于完整描述飞秒激光加热金属薄膜/基底时的整个热量传递过程.同时在300 K温度下,采用背面抽运-表面探测瞬态热反射法实验研究了飞秒脉冲激光加热金属薄膜的热量传递过程,理论预测曲线和实验测量结果符合较好,验证了理论模型的正确性.基于此模型测量得到了金薄膜的电子-声子 关键词： 飞秒脉冲激光 电子-声子耦合 界面热导 瞬态热反射     

在SrTiO3、LaAlO3和Y-ZrO2衬底上外延生长La1.85Sr0.15CuO4、La2CuO4和Nd1.85Ce0.15CuO4、Pr2CuO4薄膜

利用脉冲激光法研究了在（１００）ＳｒＴｉＯ３（ＳＴＯ）、（１００）ＬａＡｌＯ３（ＬＡＯ）和（１００）Ｙ－ＺｒＯ２（ＹＳＺ）衬底上外延生长ＬａＣｕＯ４（ＬＣＯ）,Ｌａ１．８５Ｓｒ０．１５ＣｕＯ４（ＬＳＣＯ）,Ｎｄ１．８５Ｃｅ０．１５ＣｕＯ４（ＮＣＣＯ）和Ｐｒ２ＣｕＯ４（ＰＣＯ）薄膜的工艺技术。利用Ｘ光衍射仪检测了不同条件下制备的薄膜样品结构和取向。Ｘ射线衍结果表明,在事适的制膜条件下可以在这三种衬底     

溶胶—凝胶法制备CdS微晶掺杂TiO2／SiO2薄膜及其非线性光学特性

采用溶胶－凝胶方法在普通的载玻片上制备了ＣｄＳ微晶掺杂的ＴｉＯ２／ＳｉＯ２复合薄膜。用正硅酸乙酯、钛酸丁酯、醋酸镉作原料，比较了两种硫化剂：硫尿和硫代乙酰氨的硫化作用。Ｘ射线衍射谱和拉曼光谱揭示了ＣｄＳ微晶镶嵌在ＴｉＯ２／ＳｉＯ２薄膜的玻璃网络中。不同热处理温度、不同热处理时间的吸收光谱表明薄膜中存在着量子尺寸效应。采用Ｚ扫描技术测量了薄膜的非线性吸收及非线性折射率ｎ２＝－４．６７×１０－７ｅｓｕ。     

缺氧La0.6Ca0.4MnO3-δ薄膜的光响应特性

采用波长均为532 nm的连续激光和脉冲激光研究了缺氧La0.6Ca0.4MnO3-δ(LCMO)薄膜的光响应特性。分析了在金属态和绝缘态时,缺氧对LCMO薄膜光响应的不同影响。在脉冲宽度7 ns、峰值功率750 mW的脉冲激光作用下,缺氧LCMO薄膜在室温下呈现出明显的光响应信号,其光电导增大36.4%,上升时间约30 ns。由于光子能量大于LCMO的禁带宽度,光子注入在薄膜中产生了电子-空穴对,而电子很容易被氧空位俘获,从而在薄膜中产生大量额外的空穴载流子,大量的空穴载流子可能诱发局域绝缘-金属相变,从而在薄膜中产生明显的光电导效应。实验显示出缺氧钙钛矿薄膜在光电器件上的巨大应用潜力。     

用于超短激光脉冲检测的新型光电发射薄膜

Ａｇ－Ｂａ－Ｏ薄膜是金属超微位子埋藏于半导体基质中的全新型光电转换薄膜。它不含碱金属，有很好的稳定性，可以在大气中存放，再置入真空系统中不需要激话，就能产生足以检测皮秒级激光脉冲信号的光电子发射。在激光作用下有特殊的灵敏度。这种光电转换薄膜有很好的应用前景。     

PbTiO3超微粒-硬脂酸复合LB膜的光谱特性

ＰｂＴｉＯ３超微粒－硬脂酸复合超薄膜用ＬＢ膜技术制备,用π－Ａ曲线和原子力显微镜进行膜性能的表征。紫外－可见光吸收光谱、荧光光谱和拉曼光谱表明：ＰｂＴｉＯ３超微粒及其复ＬＢ膜具有量子尺寸效应和介电限域效应。     

Nonlinear optical properties of composites based on conductive metal-alkanoate liquid crystals

The dynamic holography in new composite materials based on a novel class of metal-alkanoate ionic liquid crystals (ILCs) is studied experimentally and theoretically. The composites are formed as a dielectric dye film covered by lyotropic metal-alkanoate ILC and ionic smectic glasses with doped dye molecules. The dynamic gratings are created by nanosecond pulses of double frequency Nd:YAP laser, the recording demonstrates fast erasure time of residual thermal gratings. The nonlinear optical properties are determined by the resonance nonlinearity in photosensitive centres of ILC. Note, that permanent relief gratings will be formed on a dielectric dye film only as well as in composite cells either with nematic LC or with polymers under action of pulsed laser radiation. Lyotropic ILC layer applied over the dye film provides the dynamic regime of grating recording in composite cells. We found a secondary thermal grating is much smaller, the conductive ILC matrix provides effective heat dissipation and erasure of this thermal grating. A theory of Raman-Nath self-diffraction holography on thin films followed from the wave equation and the nonlinear mechanism of absorption saturation is developed to explain experimental results.     

金属光学薄膜的激光化学沉积法

评述薄膜光学技术的发展动向及铜、金、铝光学薄膜的激光化学汽相沉积法。     

The structuralization phenomena in magnetic fluid composites and their influence on transmissivity of light

A magnetic field induced agglomeration of magnetic and μm-sized copper non-magnetic particles in magnetic fluid with several volume concentrations of magnetite and copper particles was studied by means of optical microscope equipped with video camera. Transmission of light through two crossed polarizers and thin magnetic fluid and magnetic fluid composites film as a function of magnetic field was investigated. The experimental data showed that the presence of copper particles influences the aggregation processes of magnetic particles in magnetic fluids and transmissivity of light. Dedicated to Dr. Anton Zentko on the occasion of his 60th birthday. This work was supported by the Slovak Academy of Sciences within the framework of Project GAV No. 4001.     

Photoinduced drift of electrons in thin magnetic films

The results are presented of experimental studies of variations in the polarization of light reflected from multilayer thin metal films containing nonmagnetic Bi or Ti films and a TbFe magnetic film magnetized in the direction perpendicular to the film plane. An additional optical rotation of light reflected from bismuth and titanium films was observed upon their irradiation by intense nanosecond pulses from a semiconductor laser. This optical rotation is attributed to the photoinduced drift of electrons with polarized spins from the magnetic TbFe film.     

Laser annealing of silica glass with ion-synthesized copper nanoparticles

The action of KrF excimer laser radiation on the composite material consisting of the silica glass with copper nanoparticles is investigated as a function of the number of nanosecond laser pulses. Metal nanoparticles are synthesized by ion implantation. It is established using optical reflectance measurements of composite layers that, at the initial stage, the irradiation leads to the fragmentation of the largest nanoparticles. Then, after irradiation by several pulses, the particles become larger due to the heating of the glass. The laser treatment for a longer time (several tens and hundreds of pulses) results in the dissociation of nanoparticles into small clusters and individual atoms. The mechanisms responsible for the modification of the composite material under high-power laser radiation are discussed.     

Structure and reflective properties of Al-Cu-Fe quasicrystalline thin film prepared by laser induced arc method

Al-Cu-Fe thin films were prepared by laser induced arc (laser-arc) method from a single source-Al63Cu25Fe12 alloy, which was proved to consist of quasicrystalline phase together with approximant phase. The composition of the deposited films meets the requirement for formation of icosahedral symmetry phase. Quasicrystalline phase was obtained after annealing the amorphous as-deposit film samples. The optical properties of the samples were investigated. Thin film samples of Al, Cu and Fe deposited under the same condition were employed for comparison. The results showed specific reflective properties of Al-Cu-Fe quasicrystal thin film in some wavelength range. The optical conductivity of the films exhibited a negative peak, centered about 440 nm in range of 190to 800 nm. The Al-Cu-Fe quasicrystal thin films could absorb almost all the ray in the wavelength range from 420nm to 450 nm. The ratio of absorption was greater than 99%.     

Limit analysis for laser removal of micron contaminant colloidal silicon dioxide particles from the super-smooth optical glass substrate by pulse Nd:YAG laser

Multimode Nd:YAG pulse laser was applied to remove micron and submicron particles by vaporizing a thin paint film pre-coated on super-smooth optical substrate surface. By analyzing the poor absorption of the optical glass substrate to the irradiative Nd:YAG pulse laser, the removal mechanism of contaminated colloidal particles from the super-smooth surface through vaporization of a volatile solid film is described. A limit analysis was proposed to determine the lower and the upper threshold of laser fluence for cleaning the SiO₂ contaminants from super-smooth K8 optical substrate. Relevant experiments on laser cleaning of micron-polishing particles from super-smooth K8 optical substrate confirmed the usefulness of this method in assisting the selection of effective cleaning fluence for accomplishing high cleanliness, which was in a range of 80–90% of the predicted upper threshold.