利用渡越辐射研究超热电子在固体靶中的输运过程

为了探索超热电子的输运过程，在100 TW掺钛蓝宝石飞秒激光器上利用光学CCD相机和OMA光学多道分析仪，分别在靶背表面法线方向测量了光发射空间分布图案和光谱. 实验测量结果显示，光发射空间分布图案呈圆盘状，在圆盘中明亮而强的光信号呈局部化分布，该现象表明，超热电子在输运的过程中存在成丝效应，引起严重的不稳定性；光发射光谱在3倍频和3/2倍频附近出现尖峰，分别是3次谐波和3/2次谐波，这一现象归因于超热电子束在传输的过程中产生的微束团而引起的相干渡越辐射(CTR)；光发射光强随靶厚度的增加而减小. 关键词： 超热电子 相干渡越辐射 输运 不稳定性     

Optical limiting in Pluronic F-127 hydrogel with nanocarbon inclusions

Characteristics of nonlinear optical limiting (limiting curves) of laser radiation in aqueous polymer systems with nanocarbon inclusions have been studied. Suspensions of nanotubes and soot stabilized by the amphiphilic polymer Pluronic F-127, the additives of which provide the system’s transition to a solid-like hydrogel aggregate state at room temperature, have been considered. The limiting materials after their optical breakdown by high-intensity radiation in the gel state have been regenerated using the thermoreversible hydrogel–isotropic solution phase transition. These systems are shown to be promising for self-healing optical materials.     

Dosimetric investigations of laser-induced phase transition of MX1-cell membranes by use of quantum dots

It is well known that laser scattered-light applicators when applied for laser-induced tumor therapy allow the precise thermal destruction of metastases. Using laser radiation in the NIR spectral range (usually, Nd:YAG laser systems λ = 1064 nm), a penetration depth of 5–10 cm (1/e is the decrease in radiation intensity) is achieved in biological tissues. The major tissue-optical parameters, i.e., absorption coefficient μ_a, scattering coefficient μ_s, and the anisotropy factor g, show biological tissues to be strongly scattering media which have a so-called optical window in the NIR. As a consequence, the therapeutic laser radiation is scattered and absorbed at a deeper level, leading to a virtual enlargement of the laser applicator. The thermal sclerotization and the thermal cell damage originate within the absorbing volume of the laser radiation and spread outward by thermal diffusion. There are three dosimetrically relevant zones of thermal and biological damage: (1) a zone of thermal coagulation; (2) a threshold of partial necrosis (destruction of all metabolic processes in the cell is the maintenance of essential parts of the cytoskeleton and the plasma membrane); this is characterized by a specific temperature range, the so-called phase transition, which refers to the transition from the gel phase of the biomembrane to the fluid phase; the determination of this temperature zone is an integral part of the following experimental investigations on MX1 cells; (3) an external zone of thermal effects made up of partial and multiple damage with a statistical chance of survival. This paper describes the investigations on heat stress in cancer cells to verify the maximum phase transition of the outer MX1 cell membranes and the related results. For this purpose, a novel method of quantum dot fluorescence dosimetry was developed. The evaluation of the measured laser-induced fluorescences yields a first approximation of the determination of the phase transition on MX1 cells.     

Observation of coherent transients by use of current switching of a semiconductor diode laser

We have observed optical free induction decay on the (3)H(6)(1) ? (3)H(4)(1) transition of Tm(3+) ions in LaF(3), using an external-cavity diode laser. The diode-laser frequency was switched by the application of a current step, and the resulting transient was detected by heterodyne beating with the laser at its new frequency. This provides a simple new way to measure coherent transients. The beat note shows a frequency chirp that gives a real-time measure of the diode-laser frequency. This result is attributed to changes in the laser lattice temperature on the microsecond time scale.     

Phase-locked optical divide-by-3 system for visible radiation

An optical divide-by-3 system has been developed to phase lock a diode-pumped Tm:YAG laser at 148 THz (2022 nm) to a frequency near 1/3 that of an ultrastable diode laser system at 445 THz (674 nm). The 148-THz radiation is frequency doubled in angle-tuned AgGaS(2) and frequency differenced with the 445-THz radiation in noncritically phase-matched LiNbO(3) , generating two signals at 297 THz, which are mixed on a photodiode. An electronic servo system is used to control the frequency of the Tm:YAG laser and to phase lock it to the visible diode laser output. Phase-locking periods of several minutes are routinely obtained.     

飞秒激光-固体靶相互作用中渡越辐射的测量

为了探索超热电子的加热机制,利用光学CCD相机和OMA光学多道分析仪,分别在靶背法线方向测量了光学渡越辐射（OTR）积分成像图案和光谱。实验在100 TW掺钛蓝宝石激光器上进行,飞秒激光与铜膜靶作用后,靶表面发光信号由空间分辨装置聚焦成像并引到CCD或OMA谱仪的狭缝上。测得的积分成像图案呈圆环状,光斑形成区域直径约为225 μm,在圆环边缘附近出现局部化明亮光信号,该现象表明,超热电子在传输的过程中存在成丝效应,其分布也不均匀。光谱在300～500 nm之间出现一系列非周期锐利尖峰,在400 nm（2ω0）附近出现的尖峰应归因于v×B加热机制产生的超热电子引起的相干渡越辐射（CTR）。     

飞秒激光-固体靶相互作用中渡越辐射的测量

 为了探索超热电子的加热机制，利用光学CCD相机和OMA光学多道分析仪，分别在靶背法线方向测量了光学渡越辐射（OTR）积分成像图案和光谱。实验在100 TW掺钛蓝宝石激光器上进行，飞秒激光与铜膜靶作用后，靶表面发光信号由空间分辨装置聚焦成像并引到CCD或OMA谱仪的狭缝上。测得的积分成像图案呈圆环状，光斑形成区域直径约为225 μm，在圆环边缘附近出现局部化明亮光信号，该现象表明，超热电子在传输的过程中存在成丝效应，其分布也不均匀。光谱在300～500 nm之间出现一系列非周期锐利尖峰，在400 nm（2ω0）附近出现的尖峰应归因于v×B加热机制产生的超热电子引起的相干渡越辐射（CTR）。     

超强脉冲激光辐照固体靶背表面的渡越辐射

 在超强脉冲激光与固体靶相互作用中,利用光学CCD相机和光学多道分析仪,分别在固体薄膜靶背表面法线方向测量了渡越辐射（TR）积分成像图案和光谱。测量结果显示：TR空间分布图案呈圆环状,而辐射区域有发散角和光强分布;TR光谱在800 nm附近出现尖峰,是激光的基频波,这一现象归因于超热电子束在输运的过程中产生的微束团而引起的相干渡越辐射;如果考虑超热电子的产生和加热机制,共振吸收和真空加热对超热电子都有贡献,其中占主导地位的加热机制则是共振吸收对电子的加热。     

Bioferroelectricity and biopiezelectricity

The piezoelectric and nonlinear optical properties of diphenylalanine peptide tubes have been investigated. The structure of peptide tubes has been studied, and the analysis of the anisotropy of the piezoelectric and nonlinear optical responses during the thermally induced phase transition (T = 150°C) has been performed. It has been shown that, both during homogeneous and local heatings in a laser beam, the observed phase transition is reconstructive.     

超强脉冲激光辐照固体靶背表面的渡越辐射

在超强脉冲激光与固体靶相互作用中,利用光学CCD相机和光学多道分析仪,分别在固体薄膜靶背表面法线方向测量了渡越辐射（TR）积分成像图案和光谱。测量结果显示：TR空间分布图案呈圆环状,而辐射区域有发散角和光强分布;TR光谱在800 nm附近出现尖峰,是激光的基频波,这一现象归因于超热电子束在输运的过程中产生的微束团而引起的相干渡越辐射;如果考虑超热电子的产生和加热机制,共振吸收和真空加热对超热电子都有贡献,其中占主导地位的加热机制则是共振吸收对电子的加热。     

超热电子输运背向光辐射的实验研究

在100TW掺钛蓝宝石飞秒激光器上利用光学CCD相机和光学多道分析仪,分别在靶背法线方向测量了超热电子光辐射的空间分布和光谱.测量结果显示：光辐射空间分布图案呈圆环状,而辐射区域有发散角和光强分布,且包含多种辐射成分.光辐射光谱在800nm附近出现尖峰,是激光的基频(ω₀)波,这一现象归因于超热电子束在输运的过程中产生的微束团而引起的相干渡越辐射(CTR).随着激光能量的增加,CTR光谱峰向红光方向移动,基频波红移的主要原因是由于等离子体临界面的迅速膨胀.如果考虑超热电 关键词： 超热电子 光辐射 共振吸收 红移     

Electron dynamics in the laser and quasi-static electric and magnetic fields

3/2 dimensional Hamiltonian equations, accounting for arbitrary polarized plane wave laser radiation and arbitrary electric and magnetic fields in the directions both along and across to the direction of the laser beam propagation, are derived for superluminal phase velocity of the laser radiation. An impact of superluminal laser radiation phase velocity on the transition to stochastic electron motion is studied.     

Absolute frequency measurement of the In+ clock transition with a mode-locked laser

The absolute frequency of the In(+) 5s(2) (1)S(0)5s5p (3)P(0) clock transition at 237 nm was measured with an accuracy of 1.8 parts in 10(13). Using a phase-coherent frequency chain, we compared the (1)S(0)(3)P(0) transition with a methane-stabilized HeNe laser at 3.39 mum, which was calibrated against an atomic cesium fountain clock. A frequency gap of 37 THz at the fourth harmonic of the HeNe standard was bridged by a frequency comb generated by a mode-locked femtosecond laser. The frequency of the In(+) clock transition was found to be 1 267 402 452 899.92 (0.23) kHz, the accuracy being limited by the uncertainty of the HeNe laser reference. This result represents an improvement in accuracy of more than 2 orders of magnitude over previous measurements of the line and now stands as what is to our knowledge the most accurate measurement of an optical transition in a single ion.s.     

Phase-transition radiation and the growth of a new phase

It was shown that, under certain conditions, the growth of a new phase becomes much like a cooperative optical phenomenon during which the heat of phase transition evolves as a sequence of superradiance pulses (phase-transition radiation). The optical control of new-phase growth and the effect of optical properties of substances on the kinetics of phase transitions are considered.     

飞秒激光与固体靶相互作用中光辐射时间特性的实验研究

为了探索光辐射的时间特性, 在100 TW掺钛蓝宝石飞秒激光器上利用光学条纹相机, 分别在靶背表面法线方向测量了光辐射的时间积分和时间分辨成像光斑. 实验测量结果显示: 光辐射时间积分成像光斑呈长条状, 而辐射区域有发散角、有光强分布, 包含多种辐射成分; 光辐射的时间分辨成像光斑进一步证明, 渡越辐射(TR) 是信号强而快, 持续时间短, 为皮秒(ps) 量级, 是最先到达屏幕上, 并推算出相应的持续时间为85.5ps. 其他成分光辐射是信号弱而慢, 持续时间长, 为纳秒(ns) 量级, 是最后到达屏幕上. 光辐射的时间特性能为鉴别和判断TR信号提供了新的依据.     

飞秒激光渡越辐射时间特性的实验研究

为了探索渡越辐射（TR）的时间特性，在100 TW掺钛蓝宝石飞秒激光器上利用光学条纹相机，在靶背表面法线方向测量了TR时间分辨成像光斑。实验测量结果显示:TR时间分辨成像光斑呈长条状，而辐射区域有发散角、有光强分布。 TR信号强而快，持续时间短，为ps量级，最先到达屏幕上。其他成分光辐射信号弱而慢，持续时间长，为ns量级，最后到达屏幕上。TR的时间特性能为鉴别和判断TR信号提供了新的依据。     

Dye-laser threshold in a protein solution

We propose to study the cooperative effects in a system exhibiting a phase transition by measuring the temperature dependence of the threshold pumping power required for laser oscillation from organic dyes in the sample. In the present experiments, we have chosen a protein (lysozyme) as the substance with a phase transition. Comparing measurements of optical absorption, fluorescence and optical rotation spectra, we found two types of temperature-dependent phase transition in lysozyme. The role of the coherent intermolecular interaction is discussed.     

Optical lattice trapping of 199Hg and determination of the magic wavelength for the ultraviolet 1S(0)↔3P(0) clock transition

We report on the Lamb-Dicke spectroscopy of the doubly forbidden (6s(2))(1)S(0)?(6s6p)(3)P(0) transition in (199)Hg atoms confined to a vertical 1D optical lattice. With lattice trapping of ?10(3) atoms and a 265.6 nm probe laser linked to the LNE-SYRTE primary frequency reference we have determined the center frequency of the transition for a range of lattice wavelengths and at two lattice trap depths. We find the Stark-free (magic) wavelength to be 362.53(0.21) nm-essential knowledge for future use of this line in a clock with anticipated 10(-18) range accuracy. We also present evidence of the laser excitation of a Wannier-Stark ladder of states in a lattice of well depth 10E(R).     

CO2的腔增强吸收与高灵敏吸收光谱研究

腔增强吸收光谱(CEAS)是在衰荡吸收光谱的基础上发展起来的一种新型的直接吸收光谱技术.文章报道了用中心输出波长为1.573μm的窄线宽连续可调谐半导体激光器(DFB封装)作光源,用两块高反射率平凹透镜(在1.573μm附近,凹面反射率R～99.4%,曲率半径r～1 m)组成对称共焦腔作吸收池的腔增强吸收光谱系统.采用扫描腔长的方法改变谐振腔的模式,当激光器的输出频率与谐振腔的某一腔模之间满足共振匹配关系时,激光被耦合到谐振腔内,用探测器接收透过谐振腔的光信号,同时用波长计精确测量激光器的输出波长.在33.5 cm长的吸收池内测量了吸收强度为1.816×10-23cm-1·(molecule·cm-2)-1的二氧化碳分子的弱吸收谱线,探测灵敏度达到了6.78×10-7 cm-1.实验结果表明,腔增强吸收光谱具有灵敏度高,装置简单,易于操作等优点.     

二硅酸钠晶体、玻璃及其熔体结构的拉曼光谱研究

采用铜蒸气脉冲激光光源和时间分辨探测技术,实现了对ＪＹＵ１０００拉曼光谱仪的高温改造,可在样品温度高至２０２３Ｋ下稳定地测谱;二硅酸钠晶体、玻璃及其熔体的测量结果表明,高温Ｒａｍａｎ光谱不仅可分辨不同的结构相、提供固－液相变信息,而且能分析具有不同桥氧数的硅氧四面体微结构单元,即聚合状况以及它们随温度的变化,因而为物质的结构研究,特别是高温状态的熔体的研究,提供了重要的手段和依据。