多壁碳纳米管光限幅特性的研究

用化学气相沉积法制备了多壁碳纳米管,并将其溶解在甲苯溶液中.用波长为1064nm的皮秒脉冲激光测量该样品的透过率,发现了非常明显的光限幅特性.当入射光强较小时,透射光强度随入射光强度的增大而增大,输出与输入为线性关系;随着入射光强的增大,透射光强增长的速度明显变慢,并逐渐趋于饱和.当入射光强度较小时,样品的透过率接近100%;而当入射光强为8GW/cm²时,非线性透过率达到30%.根据三光子吸收理论计算,理论拟合与实验结果非常符合,说明多壁碳纳米管的三光子吸收产生了光限幅效应.实验测 关键词： 多壁碳纳米管 光限幅 三光子吸收     

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.     

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。     

甲基红掺杂碳纳米管悬浮液的光限幅特性研究

利用实验的方法研究了甲基红掺杂碳纳米管悬浮液对波长为532 nm激光的光限幅效应.分析了样品厚度和入射激光重复频率对光限幅特性的影响,并与纯碳纳米管悬浮液的光限幅特性进行了比较.实验结果表明,对于线性透过率为60%（500 nm）的碳纳米管悬浮液,掺入甲基红后其沉淀速度明显减慢,限幅阈值由250 μJ降低为200 μJ;对于2和5 mm 厚度的样品,掺杂甲基红使碳纳米管悬浮液的箝位输出激光脉冲能量分别由45和20 μJ降低为35和9 μJ. 关键词： 非线性光学 光限幅效应 甲基红 染料掺杂碳纳米管悬浮液     

全氟取代的钛酞菁衍生物的非线性光学和光限幅性能研究

制备和研究了全氟取代的钛酞菁F_(16)PcTiO及其轴向取代衍生物F_(16)PcTiO_2PhCHO的线性和非线性光学(含光限幅)性能。与F_(16)PcTiO相比,轴向取代的钛酞菁F_(16)PcTiO_2PhCHO的Q带最大峰红移了7 nm。Z-扫描实验表明,无论在甲苯溶液中还是在氯仿溶液中,F_(16)PcTiO都展现出比F_(16)PcTiO_2PhCHO更大的非线性吸收系数和低的饱和能量密度。F_(16)PcTiO_2PhCHO在氯仿溶液中的光限幅性能要明显优于其在甲苯溶液中的光限幅性能。与高度可溶的四叔丁基取代的钛酞菁(tBu_4 PcTiO和tBu_4 PcTiO_2 PhCHO)相比,十六氟取代的钛酞菁化合物具有较强的由酞菁环间范德华力驱动的分子间相互作用,这种相互作用导致材料在有机溶剂中的溶解度降低和非线性性能(含光限幅)性能下降。     

重频激光对多壁碳纳米管悬浮液光限幅特性的影响研究

在激光以不同重复频率入射下,研究了直径分布为10～20 nm的多壁碳纳米管悬浮液对波长为1064 nm激光的光限幅效应,定性分析了不同重复频率激光对多壁碳纳米管悬浮液的光限幅影响。结果表明:碳纳米管悬浮液对波长为532 nm和1064 nm的激光都具有很强的光限幅响应;在多脉冲激光入射时,碳纳米管悬浮液的光限幅效应比单脉冲激光入射时更显著。     

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.     

碳纳米管悬浮液的光限幅特性实验研究

 通过超声波降解法制备了多壁碳纳米管的水-表面活性剂悬浮液，测量了其对于1 064 nm，脉宽10 ns Nd:YAG调Q脉冲激光的光限幅曲线。实验发现：入射激光能量密度较低时，出射能量密度随入射能量密度的增加而线性增加；当入射能量密度为160 mJ/cm²时，出射能量不再线性增加并且逐渐趋近于光限幅器的嵌位输出值，约16 mJ，同时，对激光的透过率从71%下降到15%。通过Z扫描和探针光实验以及45°散射角下散射能量、散射率随入射激光能量变化曲线的测量，对碳纳米管悬浮液的光限幅机理进行了研究。结果表明：其限幅机理可能源于碳纳米管吸收激光能量后升华产生的膨胀的碳气泡对入射激光产生的非线性散射；另外，非线性折射对光限幅效果也有一定的作用。     

氧化石墨烯/壳聚糖复合薄膜材料的制备及其非线性光限幅效应的研究

石墨烯及其衍生物作为新型碳纳米结构,由于其优异的光限幅性能而受到广泛关注,但现有的工作多侧重于其在液相体系中光限幅效应及其起因研究.本文以壳聚糖为成膜基质,将氧化石墨烯(GO)与壳聚糖(CS)在液相中均匀共混后成膜,对比研究GO溶液和GO-CS复合膜的光限幅效应及其起因.结果表明在线性透过率相同的情况下,GO在固相基质中表现出比液相基质更强的光限幅效应和更弱的非线性散射.这说明不同于碳纳米管简单的非线性散射,在GO中可能存在多种非线性光学效应.     

聚对苯撑乙烯衍生物/氯仿溶液的自衍射及光限幅特性的研究

用532 nm基模高斯光束对2-甲氧基5-丁氧基取代聚对苯撑乙烯的氯仿溶液进行激光诱导衍射实验及光限幅特性的研究.实验发现,当高斯光束通过样品溶液时,在远场处出现衍射环;随着入射功率的增大,衍射图案会发生显著的变化.理论分析表明,该现象可以用光克尔效应、热效应作用下的附加相位孔对入射光束的衍射行为来解释.还进一步研究了532 nm激光作用下样品溶液的光限幅特性,根据实验结果分析得出:由热效应引起的自衍射是产生光限幅特性的主要机制.     

Optical Limiting Properties of Two Soluble Polymer/Multi-Walled Carbon Nanotube Composites

Two soluble polymer grafted multi-walled carbon nanotubes （MWNTs）, including poly（N-vinylcarbazole）-MWNTs and poly（methyl methacrylate）-MWNTs, are synthesized. Their nonlinear optical properties and opticaJ limiting （OL） performances are investigated by z-scan method with 527nm nanosecond laser pulses. These grafted MWNTs dissolved in chloroform show much better optical limiting performance than those of MWNTs and C60 in toluene solution. Nonlinear absorption and nonlinear scattering mechanism are taken into consideration for explaining the observed results. The comparison of the experimental results shows that nonlinear absorption is the dominant mechanism for OL performance of these new samples.     

Broadband optical limiting performance of polymer-wrapped carbon nanotubes in the orange-NIR region

Soluble multi-walled carbon nanotubes (MWNTs) have been obtained by noncovalent modification with poly [2-methoxy,5-(2′-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV). For the composite MWNT/MEH-PPV, there is π-π interaction between the MEH-PPV and MWNTs in addition to the wrapping of the polymer. The nonlinear optical transmittance was measured using a nanosecond optical parametric oscillator pumped with a Nd:YAG system. Excellent optical limiting performance of the composite MWNT/MEH-PPV was observed both in the visible region of 590-680 nm and at the wavelength of 1064 nm. By means of time-correlated single-photon counting fluorescence measurement, an explanation based on the nonlinear absorption of MWNT dominated by the intermolecular energy transfer was proposed.     

Enhanced optical limiting properties in suspensions of CdO nanowires

Optical limiting (OL) properties of CdO nanowires in water and ethanol were investigated by using nanosecond laser pulses at 532 nm. Experimental results show that suspension of CdO nanowires in ethanol exhibits better OL property than solution of C₆₀ in toluene and suspension of CdO nanowires in water. The dominant mechanism for the observed enhanced optical limiting in ethanol suspensions of CdO nanowires is due to nonlinear scattering.     

Synthesis of anatase titania-carbon nanotubes nanocomposites with enhanced photocatalytic activity through a nanocoating-hydrothermal process

Anatase TiO₂ nanoparticles were covalently anchored onto acid-treated multi-walled carbon nanotubes (MWNTs) through a nanocoating-hydrothermal process to obtain TiO₂-MWNTs nanocomposites. The composition and structural properties of the nanocomposites were characterized by XRD, BET, TG, TEM, HRTEM, EDX, XPS, and FTIR, and the formation of ester-bond linkage between TiO₂ nanoparticles and MWNTs was demonstrated. The enhanced photocatalytic activity of TiO₂-MWNTs nanocomposites was probed by photodegradation reaction of methylene blue under visible-light irradiation.     

可溶性聚噻吩甲烯包覆碳纳米管的三阶非线性光学响应

采用原位聚合的方法合成了聚(3-己基噻吩)-2,5-二(4-羟基-3-甲氧基苯甲烯)包覆的多壁碳纳米管(PHTHMOBQ/MWNTs). 荧光光谱分析表明, PHTHMOBQ/MWNTs复合体中, 碳纳米管与共轭聚合物PHTHMOBQ之间形成光致电子转移体系, 使得π电子离域程度增加, 并且导致荧光量子效率降低. 根据E_g与入射光子能量hν的关系, 拟合了PHTHMOBQ/MWNTs薄膜的光学禁带宽度. 发现随着碳纳米管含量的增加, E_g逐步减小. 采用简并四波 关键词： 共轭聚合物 碳纳米管 光致电子转移 三阶非线性光学效应     

Poly(N-vinyl carbazole)-grafted multiwalled carbon nanotubes: Synthesis via direct free radical reaction and optical limiting properties

In this work, samples of poly(N-vinyl carbazole) (PVK)-grafted multiwalled carbon nanotubes (MWCNTs) were synthesized via free radical reaction. The ready-made PVK was allowed to react directly with MWCNTs at 70 °C in the presence of azo-bis-isobutyronitrile (AIBN). The purified deep grey products, which can dissolve in common organic solvents such as chloroform and 1,2-dichlorobenzene (DCB), were then characterized by FTIR spectra, TEM, TGA, elemental analysis, XPS, UV-vis spectra and Raman spectra. It was confirmed that PVK chains were grafted onto the surface of the carbon nanotubes (CNTs). The optical limiting properties of these PVK-grafted MWCNTs samples were investigated by open-aperture z-scan method. All of the samples of PVK-modified carbon nanotubes in chloroform showed optical limiting behavior better than that of C₆₀ in toluene.     

Third-order nonlinear optical properties of graphene composites: A review

Graphene has excellent thirdorder nonlinear optical (NLO) properties due to its unique electronic band structure and wideband gap tunability. This paper focuses on the research progress of graphene and its composite materials in nonlinear optics in recent years. In this review, recent results on graphene (or graphene oxide)-metal nanoparticles (G-MNPs), graphene-metal-oxide nanoparticles (G-MONPs), graphene-metal sulfide nanoparticles (G-MSNPs), and graphene-organic molecular composites (G-OM) have been discussed. In addition, the enhancement mechanism of nonlinear absorption (NLA) and optical limiting (OL) have also been covered.