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.     

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     

罗丹明染料激发态吸收及非线性荧光效应研究

系统研究了罗丹明6G和罗丹明B的非线性吸收特性和荧光猝灭特性,结果表明它们在532nm的激光波长作用下,呈饱和吸收特性,在355nm的激光波长作用下呈现反饱和吸收特性,通过理论拟合得到了激发态吸收截面和能级寿命;并对荧光猝灭现象进行了解释,首次提出激发态吸收诱导荧光猝灭的理论.     

有机分子激发态非线性吸收的瞬态特性研究

提出了一种通过测量单脉冲光的输入与输出波形来研究激发态非线性吸收的新方法，用这种方法研究了纳秒脉作用下类卟啉镉溶液与甲基橙溶液的三重激发态的非线性吸收特性，前者为反饱和吸收现象，后者是由饱和吸收转化为反饱和吸收的新现象，实验结果验证了理论模拟和正确性。     

有机化合物ZnTBP/CA/PhR的非线性光吸收谱测定

测定了新型光功能有机材料锌 四苯并卟吩 巴豆酸 苯氧树脂 (Zn Tetrabenzoporphin CrotonicAcid/PhenoxyResin ,简称ZnTBP/CA/PhR)体系薄膜样品在可见光范围内的吸收谱 ,定点测量了其主要吸收谱带在激光作用下的变化情况 ,实验观察到此种材料显著的饱和及反饱和吸收现象 ,还首次观察到它的再反饱和过程。文章定性分析了变化过程中的物理机制 ,讨论了ZnTBP/CA/PhR的非线性吸收特性在光子学领域的一些应用     

基于反饱和吸收的无腔光学双稳态

本文研究了有机材料基于反饱和吸收的瞬态无腔光学双稳特性，以有机材料酞菁铜为例，理论计算得到了基于反饱和吸收的无腔光学双稳回线，实验上首次观察到酞菁铜溶液的增强吸收型无腔光学双稳态，理论计算与实验结果一致。     

新型卟啉衍生物反饱和吸收研究

利用纳秒脉冲激光下的z扫描方法对两种新型卟啉衍生物在450 nm—490 nm范围内的反饱和吸收进行了研究.通过与四苯基卟啉的比较发现，在Soret和Q吸收带之间，两种新型卟啉衍生物都具有大的反饱和吸收.采用五能级模型对实验结果进行了分析，比较了在不同波长范围内各个样品的优势.实验结果表明，在450 nm—490 nm范围内，两种新型的卟啉衍生物有着比四苯基卟啉更好的光限制应用前景. 关键词： 反饱和吸收 z扫描')" href="#">z扫描 卟啉衍生物     

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．     

偶氮苯光致异构反饱和吸收的光学双稳态开关的理论研究

讨论了稳态条件下,反饱和吸收的偶氮苯分子光学双稳态的开关性能.先根据偶氮苯光致异构的理论模型,计算了影响偶氮苯反饱和吸收系数的因素,然后理论模拟其反饱和吸收的光学双稳态开关过程.模拟结果表明:基于偶氮苯分子的反饱和吸收可实现双稳态全光开关.增大偶氮苯分子的顺式基态吸收截面,减小热弛豫系数K能够降低反饱和吸收偶氮苯光学双稳态的开关能量;反式吸收截面大不利于反饱和吸收光学双稳态的形成.     

反饱和特性化合物锌四苯并卟吩巴豆酸苯氧树脂的光吸收谱测定

报道一种新型的有机材料锌—四苯并叶吩—巴豆酸—苯氧树脂(缩写为Zntbp—CA—PhR)体系薄膜样品的吸收谱的测定，及其主要吸收谱带在激光作用下的变化情况及动力学过程。实验观察到此种材料显著的饱和及反饱和吸收现象，并观察到它的再反饱和过程，定性分析了变化过程中的物理机制。这种特征在可见光波段一个较宽的区域内都会出现。所获结果为此种有机材料在光谱域信息存储和光学限制等方面的应用提供了理论和实验依据。     

Wavelength-dependent nonlinear absorption of gold nanocages

The dipole resonances of gold nanocages were investigated theoretically using finite difference time domain method.The results show that field enhancement is obtained at the walls of the gold nanocages.It is believed that the effect can cause a strong optical nonlinear property.To test the hypothesis,nonlinear absorption was investigated using a broadband 5 ns Z scan.It was found that at low intensities the sample shows saturable absorption(SA),while at higher intensities a switch from SA to reverse SA occurs.Moreover,the nonlinear absorption of the sample is sensitively wavelength-dependent,and,in the resonant region,saturation intensity is the largest.     

Effects of solvent on nonlinear absorption properties of tetraphenylporphyrin compounds in the nanosecond regime

The nonlinear absorption properties of tetraphenylporphyrins (TPP) in different solvents and excitation intensities are investigated with nanosecond pulses by the Z-scan technique. The nonlinear absorption behaviour observed presents a distinct difference between in solvent mixtures and in pure solvents. A crossover from reverse saturable absorption (RSA) to saturable absorption (SA) and then again to RSA is observed with the increases of excitation intensity in chloroform and pyridine mixed solvents. However, porphyrin molecules in pure solvents show good RSA behaviour under the studied intensity range, no saturation absorption is observed with nanosecond excitation. Excited state absorption parameters and two-photon absorption coefficients are obtained by theoretical fit using rate equations for population densities in a seven-level energy scheme.     

酞菁铜染料的反饱和吸收动力学

本文用速率方程研究了酞菁铜染料氯仿溶液的反饱和吸收的动力学过程,并用YAG倍频调Q脉冲激光入射该样品,验证了理论.通过理论曲线与实验结果的拟合,估算出酞菁铜三重态激发态的吸收截面为2.6×10~(-17)cm~2.     

Z-scan analytical theory for material with saturable absorption and two-photon absorption

By using the Adomian decomposition method, we present the transmitted optical intensity of a nonlinear medium with the concurrence of saturable absorption (SA) and two-photon absorption (TPA) processes. We obtain the analytical expression of the open-aperture Z-scan and investigate the interplay between SA and TPA in the Z-scan trace. Through Z-scan measurements at different levels of laser intensities, both the saturable intensity and TPA coefficient could be obtained quickly yet unambiguously.     

Effect of marine derived deoxyribonucleic acid on nonlinear optical properties of PicoGreen dye

We have investigated the effect of DNA on nonlinear absorption of PicoGreen dye using single beam open aperture Z-scan technique in nanosecond regime. We observed reverse saturable absorption at 532 nm for PicoGreen without DNA. In the presence of DNA, the sample begins to behave like saturable absorbers and this effect increased as the concentration of DNA was increased. The dye-intercalated DNA showed SA characteristics near the focus but exhibited RSA characteristics at the focus. Theoretical analysis has been performed using a two-photon absorption model based on nonlinear absorption coefficient and saturation intensity. Such tailoring of optical nonlinear absorption in PicoGreen makes it a potential candidate for photonic application.     

Slow light and saturable absorption

Quantitative analysis of slow light experiments utilising coherent population oscillation (CPO) in a range of saturably absorbing media, including ruby and alexandrite, Er³⁺:Y₂SiO₅, bacteriorhodopsin, semiconductor quantum devices and erbium-doped optical fibres, shows that the observations may be more simply interpreted as saturable absorption phenomena. A basic two-level model of a saturable absorber displays all the effects normally associated with slow light, namely phase shift and modulation gain of the transmitted signal, hole burning in the modulation frequency spectrum and power broadening of the spectral hole, each arising from the finite response time of the non-linear absorption. Only where hole-burning in the optical spectrum is observed (using independent pump and probe beams), or pulse delays exceeding the limits set by saturable absorption are obtained, can reasonable confidence be placed in the observation of slow light in such experiments. Superluminal (“fast light”) phenomena in media with reverse saturable absorption (RSA) may be similarly explained. The article is published in the original.     

半导体可饱和吸收镜作为被动锁模吸收体实现超短脉冲可见激光发展状况

介绍了当前国际上流行的一种用于固体激光器被动锁模以获得皮秒和飞秒宽度脉冲的新型半导体吸收体 半导体可饱和吸收镜的基本原理和制作方法。描述了利用半导体可饱和吸收镜和倍频晶体获得可见光超短脉冲激光方面的研究现状,指出半导体可饱和吸收镜的使用将会加速超短脉冲三基色激光器的研制进程。     

Wavelength dependence of nonlinear absorption in a bis-phthalocyanine studied using the Z-scan technique

The wavelength dependence of the nonlinear absorption of a bis-phthalocyanine, Nd(Pc)₂, dissolved in dimethyl formamide was studied in the rising part of the Q-band using the open aperture Z-scan technique, to determine the wavelength region over which the nonlinear absorption changes from reverse saturable absorption to saturable absorption. It was found that the sample could be used as a reverse saturable absorber, and hence as an optical limiter, up to a wavelength of about 604 nm. The imaginary part of the third order susceptibility was also calculated for these wavelengths. Resonant enhancement of the imaginary part of the third order susceptibility was clearly observed. Received: 26 April 2002 / Revised version: 30 June 2002 / Published online: 20 December 2002 RID="*" ID="*"Corresponding author. Fax: +91-484/576-714, E-mail: kpu@cusat.ac.in RID="**" ID="**"Present address: Optical Sciences Center, University of Arizona, Tucson, USA     

Flexible alteration of optical nonlinearities of iodine charge-transfer complexes in solutions

The type of donor used is found to influence greatly the optical nonlinearities of iodine charge-transfer (CT) complexes in solutions for several solvents. The magnitude and sign changes of nonlinear absorption of iodine CT complexes for different solvents as donors are observed, which implies the transition from saturable absorption to reverse saturable absorption. Compared with C60 in toluene, iodine CT complexes with toluene and benzene demonstrate larger reverse saturable absorption. Meanwhile, flexible alteration of optical nonlinearities is easily obtained by adjusting the mixture ratio of different solvents, yielding a prospective means of constructing a nonlinear medium with a large nonlinear coefficient.