碳纳米管悬浮液对532nm激光限幅机理的实验研究

通过光限幅、Z扫描、非线性吸收和散射能量分布实验,研究了碳纳米管悬浮液对532 nm激光的限幅机理以及样品厚度对光限幅机理的影响。结果表明:碳纳米管悬浮液的光限幅机理并非单纯的非线性散射,对低能量入射激光光限幅特性主要源于对入射激光的非线性吸收;对高能量入射激光,碳纳米管的吸收效应和它电离形成的微等离子体以及液体汽化所形成气泡散射效应的共同作用,使其具有较强的光限幅能力,对浓度一定的悬浮液,增加样品厚度虽然会增强其限幅效果,但却会减弱其非线性散射效应。     

有机材料ZnTBP-CA-PhR的非线性吸收和光学限幅性能

报道了一种新型有机材料ZnTBP-CA-PhR的光学非线性吸收特性，此材料在激光作用下，在可见光区域具有反饱和吸收，再反饱和吸收和饱和吸收效应.同时发现该材料优良的光学限幅性能，不仅光限幅的阈值低，而且限幅前光透射呈线性状态没有光学非线性效应.用5能级结构模型及速率方程模拟了饱和及反饱和的实验曲线，分析了非线性吸收等的物理机理.     

有机材料ZnTBP—CA—PhR的非线性吸收和光学限幅性能

报道了一种新型有机材料znTBP—CA—PhR的光学非线性吸收特性，此材料在激光作用下，在可见光区域具有反饱和吸收，再反饱和吸收和饱和吸收效应．同时发现该材料优良的光学限幅性能，不仅光限幅的阈值低，而且限幅前光透射呈线性状态没有光学非线性效应．用5能级结构模型及速率方程模拟了饱和及反饱和的实验曲线，分析了非线性吸收等的物理机理．     

一新型金属有机化合物在皮秒激光下的三阶非线性光学性质研究

利用皮秒激光光源,采用z扫描技术研究了一种新型金属有机化合物的三阶非线性光学性质以及光限幅特性.z扫描研究结果表明,这种化合物在1064 nm波长激光激发下的三阶非线性极化率χ(3)为3.8×１０-14 esu,并且存在双光子吸收.光限幅实验结果显示双光子吸收和非线性折射两种不同机制决定了该化合物的光限幅特性.     

物理参数对光限幅效应的影响

为了对抗日益严重的激光武器威胁，需要了解激光防护材料的光学性能。该文根据非线性吸收模型，推导出光限幅阈值表达式。并以表达式为理论依据，利用配位聚合物［Cd(L4)(SO4)(H2O)2］n在波长532nm、脉冲宽度为40ps的条件下所获得的实验数据，分析研究非线性吸收参数、线性透过率和有效激发态吸收截面等物理参数对光限幅效应的影响。以此为基础，研究了激光防护材料的非线性光学特性和光限幅特性，为制备光限幅材料提供了理论和实验依据。     

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。     

溶剂对光致变色材料-乙基红的光学特性影响

研究了溶剂性质对光致变色材料乙基红光学性质的影响.用吸收谱测定了乙基红染料在不同溶剂中的溶剂化位移.对相同浓度多种乙基红溶液进行了Z-scan测量,测量了不同乙基红溶液的光限幅效应,并讨论了其与溶剂之间的关系.随极性增加,吸收谱蓝移,可以通过选择不同溶剂,改变非线性材料的应用窗口.实验结果表明,在连续光照射下,乙基红溶液的非线性折射主要由热效应引起,非线性折射系数n2受溶剂的热学性质影响较大.此外,Z-scan结果中的非线性吸收为饱和吸收.至于光限幅效应,主要受热效应影响,但亦可由吸收谱预测出在某波长处的动态范围.得出的结论有助于偶氮染料作为非线性材料的应用.     

钴卟啉溶液的光限幅特性研究

对大分子有机化合物钴卟啉的非线性光学特性在 4 5 7 9,4 88和 5 14 5nm三个连续激光波长下进行了研究。用单光束z scan技术测到三个曲线均是先出现峰值后出现谷值 ,按照Sheik bahae等人的理论该样品的非线性折射率为负值 ,即样品具有热自散焦效应。反饱和吸收特性的研究结果得到三个透射率T随入射激光功率的增大而减小的曲线 ,表明该样品在这三个波长下均呈现出反饱和吸收效应。众所周知 ,热自散焦效应和反饱和吸收效应都能导致光限幅。文章的实验结果也表明 :钴卟啉在三个波长下均具有光限幅特性 ,限幅阈值随着波长的减小而减小 ;其光学限幅效果好且限幅阈值低 ,是一种有较大潜在应用价值的新型光限幅材料。因此 ,可以利用这两种效应对钴卟啉的共同作用 ,制成新型光限幅器件     

基于富勒烯C_(60)结构体系的金纳米粒子合成物光学非线性研究

使用 5 32nm ,8ns激光脉冲研究了两种新型的基于富勒烯C6 0 结构体系的金纳米粒子合成物的光学非线性 .Z scan实验结果和理论分析的比较表明 ,材料的非线性吸收强烈地依赖于材料中的配合体 ,而非线性折射主要来自金纳米粒子的贡献 .而且与熟知的C6 0 甲苯溶液光限幅特性作了比较 ,分析了光限幅机理 .     

Nonlinear optical switching and all-figures of merit in Bi2S3-xSex/PMMA nanocomposite films investigated by Z scan under visible CW laser

Bi2S3-xSex/poly(methyl methacrylate)(PMMA)nanocomposite films were prepared using microwave assisted synthesis with different compositions of x.Crystal structure,surface morphology,and optical properties were investigated to characterize the prepared nanocomposite films.The crystallinity and optical band gap of the prepared Bi2S3-xSex/PMMA were affected by x.The prepared samples showed a blue shift in the absorption edge.The laser power dependent nonlinear refraction and absorption of Bi2S3-xSex/PMMA nanocomposite films were investigated by using the Z-scan technique.The optical nonlinearity of the nanocomposite films exhibited switchover from negative nonlinear refraction to positive nonlinear refraction to negative nonlinear refraction effects,and from saturable absorption to reverse saturable absorption to saturable absorption with an increase and decrease in the composition.An interesting all-optical figure of merit was reported to assess the nanocomposite films for a practical device.It was calculated that the device all-figures of merit were based on the nonlinear response,which is important for the all-optical switching device.The results demonstrate that the optimized all-optical figures of merit can be achieved by adjusting the composition and input laser power,which can be used for the design of different all-photonic devices,and the results of nonlinear switching behavior can open new possibilities for using the nanocomposite films in laser Q-switching and mode-locking.     

Linear and nonlinear optical properties of Au/SiO2 nanocomposite prepared by P123

Mesoporous silica thin films loaded with gold nanoparticles are synthesized in the presence of EO20PO70EO20（P123）.Transmission electron microscope images show that the matrix of the nanocomposite is an ordered porous structure with a two-dimensional hexagonal phase.The wide-angle X-ray diffraction pattern implies that the nanocomposite contains gold crystals.These metallic nanoparticleembedded solid thin films show some linear and nonlinear optical properties due to their special structure and composition.Gold nanoparticles bring about surface plasmon resonance,and an absorption peak stemming from this effect has been observed.The linear absorption property is analyzed by a quantum mechanism,and the results show that it is influenced by the size and volume fraction of gold nanoparticles. Furthermore,it shows an obviously clear nonlinear optical property measured by the z-scan technique.The magnitude of the nonlinear refractive index of the nanocomposite is estimated to be about 10？ 10 cm 2 /W.     

非线性光学限幅技术与激光防护

介绍了非线性光限幅技术的基本原理，评述了单一型光限幅技术的发展以及复合型光限幅技术的最新成果。     

Nonlinear refractive and optical limiting measurements of 2-thienylchalcone derivatives under cw laser regime

The nonlinear refractive index of 2-thienylchalcone derivatives in solution was investigated using z-scan technique with a continuous wave Argon ion laser. The results show that 2-thienylchalcone derivatives exhibit a large nonlinear refractive index at 488 nm. The optical limiting behaviour based on nonlinear refractive index was also investigated. The fluorescence from the samples was recorded and the relationship between the variation of nonlinear refractive index values and optical limiting values with fluorescence intensity were investigated. The results indicated that 2-thienylchalcone derivatives could be promising candidates for application on nonlinear photonic devices.     

强非线性吸收下高斯光束Z-扫描衍射理论模型

 摘要：在同时考虑非线性折射和非线性吸收的情况下，借助光的衍射理论，研究了Z-扫描技术的衍射理论模型，分析了非线性折射和非线性吸收同时存在时Z-扫描曲线的形状特征和变化规律。数值计算表明，非线性吸收相移和非线性折射相移的比值是影响接收小孔输出光功率的重要因素。要想得到好的光限幅效果，应选取非线性相移比值远小于1或远大于2的非线性材料。     

On the contribution of nonlinear scattering to optical limiting in C60 solution

We present experimental results which bring out the contribution of nonlinear scattering to the energy limiting of 527 nm, 30 ns pulses in C₆₀ solution. To perform these measurements we used a specific experimental arrangement to separate the effects of nonlinear refraction and scattering. Our results show that scattering reduces the output significantly and contributes to limiting in C₆₀ solution.     

Nonlinear optical and magneto-optical effects in non-spherical magnetic granular composite

The magnetization-induced nonlinear optical and nonlinear magneto-optical properties in a magnetic metal-insulator composite are studied based on a tensor effective medium approximation with shape factor and Taylcr-expansion method. There is a weakly nonlinear relation between electric displacement D and elcctric field E in the composite. The results of our studies on the effective dielectric tensor and the nonlinear susceptibility tensor in a magnetic nanocomposite are surveyed. It is shown that such a metal-insulator composite exhibits the enhancements of optical and magneto-optical nonlinearity. The frequencies at which the enhancements occur, and the amplitude of the enhancement factors depend on the concentration and shape of the magnetic grains.     

Time-resolved analysis of nonlinear optical limiting for laser synthesized carbon nanoparticles

Nonlinear optical limiting materials have attracted much research interest in recent years. Carbon nanoparticles suspended in liquids show a strong nonlinear optical limiting function. It is important to investigate the nonlinear optical limiting process of carbon nanoparticles for further improving their nonlinear optical limiting performance. In this study, carbon nanoparticles were prepared by laser ablation of a carbon target in tetrahydrofuran (THF). Optical limiting properties of the samples were studied with 532-nm laser light, which is in the most sensitive wavelength band for human eyes. The shape of the laser pulse plays an important role for initializing the nonlinear optical limiting effect. Time-resolved analysis of laser pulses discovered 3 fluence stages of optical limiting. Theoretical simulation indicates that the optical limiting is initialized by a near-field optical enhancement effect.     

Free-carrier absorption and optical limiting in the suspensions of CuS and Cu2O hollow spheres

In order to reveal the optical limiting mechanisms of semiconductor hollow spheres, the nonlinear optical properties of CuS and Cu₂O hollow spheres were investigated via the fluence-dependent transmittance and the nonlinear scattering measurements. The CuS and Cu₂O hollow spheres have similar morphologies and different types of optical band-gap. The experimental results show that the optical limiting performance of CuS is better than that of Cu₂O, although the nonlinear scattering of Cu₂O is stronger than that of CuS. Free-carrier absorption based on the delocalized carriers (holes) in CuS is believed to play an important role in the optical limiting effects. The merits of the structure of semiconductor hollow spheres used for optical limiting were discussed.