Nd:YAG激光在单晶硅中的四波混频相位共轭

以单晶硅作非线性介质,用调Q脉冲Nd:YAG激光作四渡混频,获得了相位共轭反射光波.从光激发电子-空穴对浓度及其所产生的相位光栅出发,理论计算了相位共轭镜的反射率.实验获得的共轭镜反射率为125%,并与实验中显示了其对相位干扰的补偿特性.     

软X射线（60—900eV）超薄膜的光学常数

用反射率方法测定了软X射线波段(60～900eV)超薄膜的光学常数.反射率测量在同步辐射光束线上完成.对测量数据做非线性最小二乘曲线拟合得出光学常数,同时还精密确定了超薄膜的膜厚与薄膜与基板表面粗度的均方根值.文中介绍了样品制备、反射率测量、数据解析及误差分析的方法,并给出了C、Au、Pt超薄膜的相应结果.     

宽带KrF激光抽运的受激布里渊散射反射率研究

实验上研究了宽带KrF激光抽运的受激布里渊散射(SBS)随抽运功率密度、介质气压和透镜焦距这三个实验参数的变化规律.在较低的抽运功率密度情况下，SBS反射率随抽运功率密度呈非线性增长；当抽运功率密度提高到一定程度，SBS反射率接近饱和；当功率密度继续增大，SBS 反射率随之下降.介质气压提高能够促进SBS的转换.透镜焦距长度的变化使SBS饱和反射率存在一峰值.理论上建立了宽带多模SBS模型，数值模拟结果与实验结果符合得很好，解释了宽带SBS反射率对实验参数的变化规律. 关键词： 宽带 KrF激光 受激布里渊散射(SBS) 反射率     

物理光学 光的偏振与色散

O436.32006010053偏振分光镜传输系数不等对非线性误差的影响=Nonlin-earity from difference between transmission coefficients ofPBSin laser heterodyne interferometer[刊,中]/钟志(哈尔滨工业大学超精密光电仪器工程研究所.黑龙江,哈尔滨(150001)),谭久彬…∥光电工程.—2005,32(9).—27-30为了减小激光外差干涉非线性误差,必须考虑偏振分光镜透过率和反射率不等对非线性误差的影响。通过分析两臂透过率与反射率不等对测量信号的影响,推导出两臂反射率与透过率不等对激光外差干涉非线性误差一次谐波和二次谐波影响的理论模型。仿真…     

有机染料溶液中简并的四波混频和位相复共轭研究(英文)

研究了近共振增强的四能级系统有机染料溶液中简并的四波混频后向反射波及前向波的位相复共轭特性。用有效长度为5mm,浓度为2.5×10~(-5)mol的叶录素A甲醇溶液作介质,当调QNd:YAG倍频泵浦光的能量为8mj时,非线性反射率为22％。 对于若丹明6G酒精溶液,在相同条件下的反射率为10％。用象差板检证了位相复共轭特性。用调QNd:YAG激光辐射作泵浦源,研究了若丹明6G酒精溶液双光子共振增强的简并的四波混频作用。当介质浓度为10~(-4)克分子,有效长度为5mm,泵浦光能量为70mj时,非线性反射率达14％。测量了非线性反射率与介质浓度及入射物波与后向反射波的强度的关系曲线。理论分析了四波混频前向波的位相复共轭特性,用调QNd:YAG倍频激光作泵浦源,若丹明6G酒精溶液作介质,实验上证实了理论的预言。另外,把四重简并的四波混频推广到二重简并的情况。用若丹明6G酒精溶液作介质,实现了由6300A到5320A的象转换。用9740有机染料二氯乙烷饱和吸收溶液作介质,实现了1.06μm到5320A的象转换。当介质长度为5mm,泵浦光束的能量为5mj时,后者的转换效率为25％。理论分析表明,用对红外近共振吸收,而对可见辐射是透明的介质可以实现高效率的红外象转换。这种红外象转换的方法还具有实时、快响应等优点。     

弱磁化等离子体中受激拉曼散射和受激布里渊散射抑制研究

本文针对典型激光聚变等离子体参数条件,利用动理学粒子模拟程序研究横向磁场和激光带宽在抑制受激拉曼散射(SRS)和受激布里渊散射(SBS)中的作用。模拟发现横向磁场对非均匀等离子体中SRS的非线性自共振增强有显著抑制作用,分析认为横向磁场作用于SRS激发的电子等离子体波(EPW)势阱中的俘获电子,使它们在横向上加速,对EPW造成非线性阻尼,同时减小EPW的非线性频移量,从而缩窄非均匀等离子体中SRS的自共振空间,极大降低SRS反射率。在此基础上利用横向磁场抑制SRS的特性,以及SBS增长对激光带宽的敏感性,提出了利用横向磁场和宽带激光将SRS和SBS同时抑制在低反射率水平的方案。在采用数十特斯拉横向磁场和实验中易于达到的千分之一量级的激光带宽时以及慢性约束聚变(ICF)相关参数下,SBS和SRS的反射率都得到了有效抑制。     

基于改进非线性劈窗算法的VIIRS中红外海面耀斑区反射率计算

传感器入瞳处接收到的中红外波段(3~5 μm)能量包含反射的太阳能量与地物自身的发射能量。通常该波段反射的太阳能量很弱,但在海面太阳耀斑区等特定情况下,被中红外通道探测到的反射太阳能量是比较可观的,且其对大气影响的敏感性较低,同时,对于搭载有在轨定标系统的卫星传感器,使用黑体定标后的中红外波段的在轨辐射性能相当稳定的。因此,考虑将中红外波段的海面耀斑区反射率作为用于反射太阳波段交叉定标的基准。基于这个想法,构建了改进的、适用于VIIRS(visible infrared imaging radiometer)中红外波段的非线性劈窗模型来计算南印度洋海面耀斑区中红外反射率。首先统计得到VIIRS M12和M13波段海面反射率的限定关系,然后使用非线性劈窗算法模拟计算海面反射率,模拟模型的不确定度为0.83%。在此基础上使用VIIRS的M12波段(中心波长为3.697 μm)太阳耀斑区数据计算选取的样本区的海面反射率。然后使用两种方法对反射率精度进行验证,精度分别为0.29%和0.23%,假设M12和M13波段海面反射率相等的反射率计算结果精度分别为2.48%和1.03%。该计算模型大大提高了精度,说明该模型用于VIIRS M12中红外波段计算海洋耀斑区反射率是有效可行的,其精度能够满足中红外波段海面反射率作为波段间定标基准的需求。     

ZnS/ZnSe周期性迭层介质中光的反射特性分析

基于光在多层介质中的传输理论,对ZnS/ZnSe周期迭层介质结构中光的反射特性作了分析和计算,由得到的Bragg反射率与光波长的关系曲线,发现当ZnS/ZnSe的折射率改变时,其Bragg反射率曲线将发生平移,平移的方向与Δn为“正”或“负”有关.据此,提出了利用ZnS/ZnSe的光学非线性特性,可能研制出光控“开关”或“光逻辑门”,用于光计算和光互连.     

X射线反射率的讨论

根据菲涅耳公式推导出X射线和可见光的反射率公式,计算了反射率随入射角的变化曲线.对X光导管的传输效率在反射率有无近似条件下的计算结果作了比较.     

基于FLM的L波段双波长EDFL的双稳态变换

提出和验证了一种L波段双波长掺铒光纤激光器(EDFL)双稳态控制变换和双波长开关切换的方法.将偏振控制器(PC)插入基于3 dB光纤耦合器的光纤环镜(FLM)中，并将该FLM用作L波段双波长级联线形耦合腔EDFL的公共腔镜，结果表明，调节PC可以改变FLM的反射率，实现对EDFL双稳态特性的有效控制，且双稳态特性随FLM反射率呈单调变化.利用这一性质，提出并证实，对于处在FLM最大反射率对应的双稳态第一跃变点和最小反射率对应的双稳态第二跃变点之间的任意固定抽运光功率，调节PC可实现两个稳态之间的相互变换和双波长之间的相互切换.     

4-硝基-4′-氨基偶氮苯的光学性质研究

采用紫外可见吸收和二次谐波产生技术研究了“推-拉”型偶氮苯分子Langmuir-Blodgett(LB)膜的光谱和二阶非线性光学特性.4-硝基-4′-氨基偶氮苯(NAA)分子能制成很好的LB多层膜,在稀溶液中以单体的反式异构体形式存在,在膜中主要以J-聚集体的形式存在,LB膜的紫外可见吸收谱的吸收峰较之溶液的发生了52 nm的红移.NAALB膜的二阶非线性极化率χ(2)为19.59×10－8 esu,一阶超极化率β值较大,约为1.974×10－29 esu.其光学二阶非线性起源于电偶极子机制.     

Large nonlinear phase shif towing to cascaded chi((2)) in quasi-phase-matched bulk LiNbO(3)

Large nonresonant effective nonlinear indices that are due to cascading have been observed by Z-scan and CCD camera measurements performed on quasi-phase-matched LiNbO(3). Positive and negative values of n(cascad)(2) were measured at temperatures symmetrically displayed with respect to the optimum phase-matching temperatures (2.39 x 10(-13) and -2.37 x 10(-13)cm(2)/W, respectively).     

Nonlinear Optical Properties of Novel Polymeric Rare Earth Phthalocyanine Studied Using Picosecond Z-Scan Technique

Three novel tri-dimensional phthalocyanine polymers, with lanthanum （LaPPc）, gadolinium （GdPPc） and ytterbium （YbPPc） as centric atoms, have been synthesized from a tetranuclear phthalonitrile. Third-order optical nonlinearities of these compounds in DMF solution are measured by a picosecond Z-sacn technique at 532 nm. It is found that all the compounds show reverse saturation absorption and nonlinear self-focus refraction effect. The second-order molecular hyperpolarizabilities are calculated to be 1.82×10^-23, 1.48×10^-23 and 1.45×10^-23 esu for LaPPc, GdPPc and YbPPc, respectively. The differences among their nonlinear optical properties are attributed to the special tri-dimensional structure and the variation in rare earth atoms.     

Third-order nonlinear optical properties of gold nanoshells in aqueous solution

The third-order nonlinear optical properties of gold nanoshells in aqueous solution have been investigated by using open- and closed-aperture Z-scan methods. The real and imaginary third-order nonlinear susceptibilities are obtained to be about -1.1422×10^-13 and -2.4302×10^-14 esu, respectively. We further have investigated the electric field enhancement for gold nanoshells in aqueous solution by means of a finite-element method and ascribed the small third-order nonlinear susceptibility to the smaller volume fraction and local field factor. PACS  42.65.Re; 78.67.Bf; 73.22.Lp     

Experimental investigations of nonlinear acoustic phenomena in polycrystalline zinc

The results of experimental and theoretical investigations of nonlinear acoustic phenomena (nonlinear losses, shift of resonance frequency, generation of the third harmonic, and nonlinear sound-by-sound damping) in polycrystalline zinc nonannealed and annealed resonating rods are presented. The measurements were carried out in the 10(-7)-10(-5) strain range at a frequency of about 3 kHz; the frequency of the weak ultrasonic pulse was about 270 kHz. The experimentally observed phenomena are described in frames of phenomenological equations of state containing elastic hysteresis and dissipative nonlinearity. The nonlinear acoustic parameters of these equations are determined by comparison between theoretical dependencies and experimental results. The influence of structural changes in zinc due to annealing on the nonlinear acoustic phenomena is shown.     

Bäcklund transformations and new solutions of nonlinear wave equations in four-dimensional space-time

Bäcklund transformations for several nonlinear field equations in four-dimensional space-time relating two solutions of the same equation (symmetry), or two different equations (dynamical), are given. These transformations can be used to generate new families of solutions and infinitely many conservation laws for nonlinear equations.Bäcklund transformations and solutions of nonlinear equations have been studied extensively in one-space and one-time dimension. We give here a fairly general method for a class of equations in four-dimensional space-time which paves the way for many further generalizations.Supported in part by the U.S. National Academy of Sciences Foundation Grant No. INT 73-20002 A01 (formerly GF-41958).     

Crystal growth and characterisation of new organic nonlinear optical materials: 6-cyano and 6-nitro-2,2-dimethyl-3,4-epoxychroman

Two chiral organic nonlinear optical materials, (3S,4S)-(−)-6-cyano-2,2-dimethyl-3,4-epoxychroman (1) and (3R,4R)-(+)-6-nitro-2,2-dimethyl-3,4-epoxychroman (2), have been grown into single crystals of cm³-size. Although both compounds crystallise in the orthorhombic P2₁2₁2₁ space group, they are not isomorphous and their crystal packings are quite different. Angle tuned type II phase-matched second harmonic generation between 0.8 and 1.064 μm has been evidenced, with effective nonlinear coefficients d_eff of 1 and 5 pm/V at 0.96 μm for 1 and 2, respectively. These values are in agreement with those estimated in the oriented gas model approximation using EFISH first order hyperpolarisability values (β₀=2.6 and 4.0×10⁻³⁰ esu for 1 and 2, respectively).     

CuO薄膜的三阶非线性光学特性研究

采用脉冲激光沉积技术在Si(100)和熔石英基片上制备了单相的CuO薄膜.通过X射线衍射仪,拉曼光谱仪,场发射扫描电镜和紫外可见光光度计对薄膜的结构,表面形貌和光学性质进行了表征. 场发射扫描电镜结果表明CuO薄膜中晶粒排列致密且分布均匀,其尺寸约为45nm.结合飞秒激光(800nm,50fs)和Z扫描方法测量了薄膜的三阶非线性光学特性,结果表明CuO薄膜具有超快的非线性光学响应且非线性折射率和非线性吸收系数均为负值,其大小分别为-3.96×10^-17 m^{2< 关键词： CuO薄膜 Z-扫描')" href="#">Z-扫描 三阶光学非线性}     

Critical Behavior of Nonlinear Properties in Percolating Superconductor/Nonlinear-Normal Conductor Networks

The critical behavior of nonlinear response in random networks of superconductor/nonlinear-normal conductors below the percolation threshold is investigated. Two cases are examined: (i) The nonlinear normal conductor has weakly nonlinear current (i)-voltage (ν) response of the form ν = ri + bi^α (bi^α-1《t and α > 1). Both the crossover current density and the crossover electric field are introduced to mark the transition between the linear and nonlinear responses of the network and are found to have power-law dependencies ～(f_c - f)^H and ～(f_c - f)^M as the percolation threshold f_c of the superconductor is approached from below, where H = ν_d - s_d > 0, M = ν_d > 0, ν_d and s_d are the correlation length exponent and the critical exponent of linear conductivity in percolating S/N system respectively; (ii) The nonlinear-normal conductor has strongly nonlinear ν-i response, i.e., i = X^να The effective nonlinear response X_e, behaves as X_e ～(f_c - f)^-W(α), where W ( α ) is the critical exponent of the nonlinear response x_e(α) and is α-dependent in general. The results are compared with recently published data, reasonable agreement is found.     

High-accuracy acoustic detection of nonclassical component of material nonlinearity

The aim is to assess the nonclassical component of material nonlinearity in several classes of materials with weak, intermediate, and high nonlinear properties. In this contribution, an optimized nonlinear resonant ultrasound spectroscopy (NRUS) measuring and data processing protocol applied to small samples is described. The protocol is used to overcome the effects of environmental condition changes that take place during an experiment, and that may mask the intrinsic nonlinearity. External temperature fluctuation is identified as a primary source of measurement contamination. For instance, a variation of 0.1?°C produced a frequency variation of 0.01%, which is similar to the expected nonlinear frequency shift for weakly nonlinear materials. In order to overcome environmental effects, the reference frequency measurements are repeated before each excitation level and then used to compute nonlinear parameters. Using this approach, relative resonant frequency shifts of 10(-5) can be measured, which is below the limit of 10(-4) often considered as the limit of NRUS sensitivity under common experimental conditions. Due to enhanced sensitivity resulting from the correction procedure applied in this work, nonclassical nonlinearity in materials that before have been assumed to only be classically nonlinear in past work (steel, brass, and aluminum) is reported.