可溶性碳纳米管Z扫描实验研究

以可溶性碳纳米管为研究对象，进行了Z扫描实验.实验中通过改变样品的参量，研究了材料在不同浓度和不同厚度下的Z扫描曲线特性；实验分别在532nm和1064nm的激光下进行，并分别进行了开孔和闭孔实验.材料的闭孔Z扫描曲线没有明显的峰谷对称结构，而开孔Z扫描曲线呈现关于原点对称的单一谷形状，表明样品存在较强的非线性吸收效应，非线性吸收可能是其主要的光限幅机理.     

可溶性多壁碳纳米管光限幅机理研究

根据光限幅与Z扫描实验研究了可溶性多壁碳纳米管的光限幅机理.通过现象分析、数据处理以及类比研究,证实材料的光限幅特征符合非线性吸收效应.对厚样品的独特现象进行了解释,讨论了其他机理的影响.根据Z扫描公式,计算了实验材料的三阶非线性系数.通过分析证实了非线性吸收在可溶性多壁碳纳米管的光限幅中发挥着主要作用.对厚介质的特殊现象进行的分析和计算表明,对于较厚介质和激光连续加热的情况下,其他机理的影响并不能完全否定,其特殊现象可能与微气泡的气穴作用有关.     

可溶性碳纳米管光限幅特性的实验研究

利用实验的方法研究了可溶性碳纳米管对波长为1064和532nm激光的光限幅效应.分析了在 不同的样品浓度、不同的样品厚度情况下可溶性碳纳米管的光限幅特性，并对溶剂也进行了 光限幅实验.实验结果表明，在各种情况下可溶性碳纳米管对1064和532nm激光具有较强的 光限幅特性. 关键词： 可溶性碳纳米管 光限幅效应 强激光防护     

可溶性高聚物-多壁碳纳米管复合物的吸收光谱和光限幅性能研究

合成了三种可溶性高聚物嫁接的多壁碳纳米管复合物,包括聚乙烯基咔唑-多壁碳纳米管复合物(MWNTs-PVK),聚苯乙烯-多壁碳纳米管复合物(MWNTs-PSt)和聚甲基丙烯酸甲酯-多壁碳纳米管复合物(MWNTs-PMMA)。合成样品的TEM图显示出高聚物成功地包裹在碳纳米管外。样品的氯仿溶液UV-Vis 吸收谱显示,复合物的紫外区与纯的多壁碳纳米管不同,有一些复杂的特征吸收峰,反映了高聚物与碳纳米管共价连接的作用。利用Z扫描技术通过527 nm的纳秒激光脉冲激发研究了这三种复合物的非线性光学性质和光限幅性能。这三种复合物的氯仿溶液的光限幅性能很相似,并且优于纯多壁碳纳米管氯仿悬浮液和C60甲苯溶液。为解释观察到的结果,研究了样品的非线性折射,非线性吸收和非线性散射机制。结果显示,非线性吸收是引起样品光限幅的主要机制。     

基于Z扫描理论的光限幅优化分析

基于Z扫描的基本理论,根据强光光束在非线性介质中的特殊传播规律,改变光路的几何排列及光阑孔径,计算了不同情况下光阑的归一化透过率,从而确定各个参数对限幅效果的影响,得出最佳的几何排布,以实现限幅器的优化设计.     

碳纳米管悬浮液光限幅机理实验

近年来，实验发现碳纳米管在光限幅中表现出良好的性质，其光限幅带宽宽，响应时间短，限幅阈值较低，使其成为继C60后又一理想的光限幅材料。为了研究其光限幅机理，测量了碳纳米管悬浮液的散射和透射能量随入射激光能量的变化，限幅过程中散射光的角度分布以及探针光随时间的变化。     

基于虚拟仪器的高精度Z扫描实验系统设计

设计了一个表征样品非线性特性的基于虚拟仪器的z扫描实验系统。利用Labview控制数字示波器TDS3012采集两路光强信号，并结合对微位移平台的控制实现Z扫描。以Nd：YAG飞秒放大器产生的800nm的飞秒激光作为探测光，经透镜聚焦后通过薄介质样品；用数字示波器测量样品在透镜焦点附近的透射光强，经过数据处理得到样品的非线性折射率和非线性吸收系数。利用该实验系统，对标准非线性吸收样品Rhodamine 6B进行了测量，计算得到其双光子吸收截面为σ^2=6．8GM（GM：10^-50cm4s photon^-1 molecule^-1），该结果与其他文献利用不同测量方法得到的结果接近，证明该实验系统的测量结果是正确的，可满足非线性测量的精度要求。     

非线性折射率测量的Z扫描方法

描述了利用会聚的单光束灵敏地测量各种非线性介质的非线性折射率和非线性吸收系数的方法。被测样品放置于会聚高斯光束的光轴上（ｚ轴），样品在焦点附近沿ｚ轴移动，在远场处放置带有小孔的屏。通过小孔测量光束通过样品后的透过率，根据透过率与样品位置的关系，即可得到非线性介质的非线性折射率和非线性吸收系数，并能确定非线性折射率的符号（自聚焦或自散焦）。给出了若干测量结果。     

厚光学非线性介质Z扫描理论分析

采用高斯分解方法，对厚光学非线性材料的Ｚ扫描进行了理论分析，得到了对于实验工作者寻找优良的光学非线性材料和合理设计光学限制器时较有用的结果。 关键词：     

强非线性吸收下Z扫描衍射模型及实验研究

根据光的衍射理论,建立了非线性光学介质对高斯光束的开孔Z 扫描理论模型.数值计算表明,当相移比值Γ≤0.15,出射光功率随入射光功率的增加出现振荡衰减现象;当Γ>0.15,在输入光强低于某一个值时,输出随输入的增加而线性增加;当输入光强超过该值后,输出功率不再增加甚至趋于零.实验采用Nd∶YAG脉冲激光,在波长为532 nm,脉宽8 ns条件下,对含3.5%和7.0%碳纳米管的聚苯胺/碳纳米管复合体薄膜（PANI/MWCNT）的非线性吸收特性进行了研究.计算表明,该类化合物的激发态吸收截面积远大于其基态吸收截面积,具有很强的反饱和吸收.     

Ester-functionalized soluble single-walled carbon nanotubes

We report the preparation of soluble ester- functionalized single-wall carbon nanotubes (sSWNT-COO(CH₂)₁₇CH₃). By use of solution phase IR spectroscopy we are able to compare the ratio of the carbon atoms in the SWNT backbone to the carbon atoms in the ester and amide functionalities of s-SWNTs. Received: 16 July 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002     

用散粒噪声测量碳纳米管中Luttinger参数

将碳纳米管的载流子输运用基本电荷为ge的Fermi液态模型描述，利用散射理论计算出纳米管中的零频率散粒噪声，在绝对零度下，存在一个强势垒的碳纳米管的散粒噪声为2geI.提出了一种测试纳米管Luttinger参数的新方法：在纳米管上形成一个强势垒，通过测试其散粒噪声，就可以计算出g因子. 关键词： 碳纳米管 Luttinger参数 散粒噪声 散射理论     

Study of optical nonlinearity of functionalized multi-wall carbon nanotubes by using degenerate four wave mixing and Z-scan techniques

The phase conjugation geometry of degenerate four wave mixing (DFWM) technique has been employed to study the third-order optical nonlinear susceptibility (χ³) and second-order hyperpolarizability of multi-wall carbon nanotubes (MWCNTs). MWCNTs were grown by thermal chemical vapor deposition method and, subsequently functionalized with carboxylic acid group to improve their solubility in an organic solvent, ethylene glycol. The average hyperpolarizability for each carbon atom has been found to be 4.74 × 10⁻⁴⁶ m⁵/V² for the pump pulse of 8 ns at 532 nm. Decreasing the pulse width of the pump laser decreases the average value of hyperpolarizability. The absorption spectra show a monotonous increase from IR through visible and give an opportunity to estimate the imaginary part of the χ³ by the open aperture Z-scan technique.     

Ultrafast nonlinear optical response of carbon nanotubes functionalized with water soluble porphyrin

A new nanocomposite is obtained by functionalizing carbon nanotubes (CNTs) with a water soluble metalloprophyrin using a simple chemical technique and characterized by optical absorption, IR, and Raman spectroscopy. Results from spectroscopic studies indicate the noncovalent nature of interaction between CNTs and porphyrin. The ultrafast nonlinear response is characterized by measuring the nonlinear absorption coefficient and refractive index by z-scan technique in the femtosecond pulse regime. The nanocomposite is found to exhibit two-photon absorption (TPA) with a reasonably large nonlinear optical coefficient, whereas pure CNTs is known to exhibit saturable absorption. Design of such water soluble nanocomposites offers scope for obtaining materials with enhanced ultrafast optical nonlinearity.     

Tunable adsorption on carbon nanotubes

We investigated the adsorption of a single atom, hydrogen and aluminum, on single-wall carbon nanotubes from first principles. The adsorption is exothermic, and the associated binding energy varies inversely as the radius of the zigzag tube. We found that the adsorption of a single atom and related properties can be modified continuously and reversibly by the external radial deformation. The binding energy on the high curvature site of the deformed tube increases with increasing radial deformation. The effects of curvature and radial deformation depend on the chirality of the tube.     

Adsorption on the carbon nanotubes

Adsorption on single walled carbon nanotubes (SWCNTs) is a subject of growing experimental and theoretical interest. The possible adsorbed patterns of atoms and molecules on the single-walled carbon nanotubes vary with the diameters and chirality of the tubes due to the confinement. The curvature of the carbon nanotube surface enlarges the distance of the adsorbate atoms and thus enhances the stability of high coverage structures of adsorbate. There exist two novel high-coverage stable structures of potassium adsorbed on SWCNTs, which are not stable on graphite. The electronic properties of SWCNTs can be modified by adsorbate atoms and metal-semiconductor and semiconductor-semi-conductor transitions can be achieved by the doping of alkali atoms.     

Filling carbon nanotubes

Received: 2 March 1998     

Super-slippery carbon nanotubes

The friction between the walls of multi-wall carbon nanotubes is shown to be extremely low in general, with important details related to the specific choice of the walls. This is governed by a simple expression revealing that the phenomenon is a profound consequence of the specific symmetry breaking: super-slippery sliding of the incommensurate walls is a Goldstone mode. Three universal principles of tribology, offering a recipe for lubricant selection are emphasized. Received 8 August 2001     

Z-scan studies on porphyrin derivative

Received: 10 January 1996 / Revised version: 15 June 1996