4，4′-二甲氨基二苯乙烯双光子吸收理论研究——溶剂效应

对最近实验室合成的分子材料4，4′-二甲氨基二苯乙烯的双光子吸收特性在从头计算的基础上进行了理论研究。理论模型是建立在密度泛函理论的基础上的。利用含时的密度泛函理论来计算分子的非线性光学性质，而溶剂效应则通过自洽响应场方法的极化连续模型来模拟。计算结果表明，三态模型可以很好地给出该分子在低激发态范围内的双光子吸收截面。随着溶剂极性的增加，单光子波长红移，双光子吸收截面增加。双光子吸收截面的大小和实验给出的结果符合得较好。     

给体位置和数目对四苯基乙烯衍生物双光子吸收性质的影响

在杂化密度泛函水平上,利用响应函数方法,计算了一类四苯基乙烯衍生物的双光子吸收性质.考虑了四苯基乙烯上给电子基团的位置和数目对双光子吸收性质的影响.并且,根据实验者采用的分子,通过增加分子的平面性和共轭长度,以及增强给体强度,理论设计了三种分子结构,并计算了它们的双光子吸收性质.结果表明,给体位置和数目对双光子吸收性质有重要影响.位于分子末端的给体取代基能有效提高双光子吸收强度.随着给体数目的增加,双光子吸收波长发生红移.在四苯基乙烯的不同侧位上添加给体取代基对双光子吸收性质的影响有明显差异.与实验者采用的分子相比,理论设计的分子结构双光子吸收截面均明显增大.当三苯胺基代替四苯基乙烯基之后,双光子吸收峰发生较大红移,双光子吸收截面明显增大.     

反-4,4''-双(N,N-二丁胺基)二苯乙烯分子双光子吸收性质研究

对于实验室合成的反-4,4'-双(N,N-二丁胺基)二苯乙烯分子,实验测量了该分子的单光子和双光子荧光谱,然后从理论上研究了其单光子和双光子吸收特性.研究结果表明,在低能量范围内,分子的单光子吸收主要发生在分子的第一激发态,而分子的双光子吸收主要发生在分子的第二和第四激发态上.该分子在相应系列衍生物中具有最大的双光子吸收截面.分子的相关能对分子的激发态能量影响较大.我们给出了分子基态与电荷转移态的电荷转移过程,并从理论上定性解释了双光子聚合反应的聚合机理.     

三苯胺衍生物分子非线性光学性质的理论研究

在密度泛函理论水平上,利用响应函数方法,研究了1-{(1E)-2-[4-(二苯胺基)苯基]乙烯基}-4-[4-N,N-二甲胺]苯(PVMB)和1-[(1E)-2-(4-(1E)-2-{4-[4-N,N-二甲胺]苯基}乙烯基)苯基]苯胺}苯基)乙烯基]-4-[4-N,N-二甲胺]苯(DPVMB)两分子的双光子吸收特性.计算结果表明,这两个化合物都具有较好的双光子吸收特性,且具有两分支结构的DPVMB分子比具有单支结构的PVMB分子有更强的双光子吸收强度.计算数值结果和实验结果符合地较好.     

4,4''-二甲氨基二苯乙烯双光子吸收理论研究--溶剂效应

对最近实验室合成的分子材料 4 ,4 ' 二甲氨基二苯乙烯的双光子吸收特性在从头计算的基础上进行了理论研究。理论模型是建立在密度泛函理论的基础上的。利用含时的密度泛函理论来计算分子的非线性光学性质 ,而溶剂效应则通过自洽响应场方法的极化连续模型来模拟。计算结果表明 ,三态模型可以很好地给出该分子在低激发态范围内的双光子吸收截面。随着溶剂极性的增加 ,单光子波长红移 ,双光子吸收截面增加。双光子吸收截面的大小和实验给出的结果符合得较好。     

N-(4-硝基苯基)马来酰亚胺分子结构、光谱和热力学性质的理论研究

N-(4-硝基苯基)马来酰亚胺是一种新合成的NPMI类化合物,在B3LYP/6-311++G~(**)水平对N-(4-硝基苯基)马来酰亚胺分子进行几何结构优化和频率、热力学性质计算,得到它的红外光谱、拉曼光谱和不同温度下的热力学性质.结果显示,该分子中两个C=O与五元环在同一个平面内,苯环上硝基中的N—O与六元环也在同一个平面内,五元环与六元环呈129.6°的二面角,整个分子不具有对称性;热容、熵、焓等热力学性质与温度之间存在很好的函数关系式.     

氧化石墨烯-卟啉复合材料光限幅性能的理论研究

利用时域有限差分法数值求解速率-场强方程,研究了一系列共价连接的氧化石墨烯-卟啉复合材料在纳秒时域内的光限幅性质和双光子吸收. 计算结果表明,氧化石墨烯-卟啉复合分子与单独的卟啉分子相比展现出增强的光限幅效应,并且有着更大的双光子吸收截面.与之前得到的含重金属的卟啉分子具有更强非线性光学性质的结论不同,不含金属元素的卟啉分子与氧化石墨烯结合后展现出了更强的非线性光学性质. 理论计算的结果与实验测量符合较好. 此外,着重研究了介质的厚度和脉冲宽度对分子双光子吸收截面的影响. 结果表明,随着介质厚度的增加或者脉宽的变宽分子的动态双光子吸收截面增大.     

(E,E)-1,4-双{2''-[5''-(B,B-二甲基苯硼)-2-噻吩基]乙烯基}-苯分子双光子吸收特性的理论研究

在密度泛函水平上,利用响应函数方法,研究了分子的单光子和双光子吸收特性.计算出了该分子在低能量范围内的最大双光子吸收截面为6.47×10-47 cm4 s/photon,与实验符合的较好.研究结果表明该分子具有较强的双光子吸收特性,是较好的双光子吸收材料.     

(E,E)-1,4-双{2''-[5''-(B,B-二甲基苯硼)-2-噻吩基]乙烯基}-苯分子双光子吸收特性的理论研究

在密度泛函水平上,利用响应函数方法,研究了分子的单光子和双光子吸收特性.计算出了该分子在低能量范围内的最大双光子吸收截面为6.47×10-47cm4s/photon,与实验符合的较好.研究结果表明该分子具有较强的双光子吸收特性,是较好的双光子吸收材料.     

D-A型二噻吩并磷杂茂衍生物分子的双光子吸收性质

在密度泛函理论理论水平上,采用响应理论方法计算了一系列2,6-donor-acceptor二噻吩并磷杂茂衍生物分子的单、双光子吸收性质.理论计算结果表明该系列分子都具有较大的双光子吸收截面,并且分子中心的磷原子无论被氧化还是金属配合,其双光子吸收截面几乎保持不变.此外,还考虑了溶剂效应对分子光学性质的影响,研究表明分子能级发生了溶剂化蓝移,并且分子的单光子和双光子吸收性质随着溶剂极性表现出非单调变化.     

Two-photon absorption properties of aggregation systems on the basis of (E)-4-(2-nitrovinyl) benzenamine molecules

Aggregation effect caused by the intermolecular hydrogen-bonding interactions on two-photon absorption properties of (E)-4-(2-nitrovinyl) benzenamine molecules is studied at a hybrid density functional level. The geometry optimization studies indicate that there exist two probable conformations for the dimers and three for the trimers. A strong red-shift of the charge-transfer states is shown. The two-photon absorption cross sections of the molecule for certain conformations are greatly enhanced by the aggregation effect, from which a ratio of 1.0:2.6:3.6 is found for the molecule and its dimer and trimer with nearly planar structures. Namely, a 30 or 20 percent increase of the two-photon absorption cross section is observed.     

The theoretical studies on the two-photon absorption properties of symmetric 1,4-bis{2-[4-（2- aryl） phenyl] vinyl }- 2,5-bisdialkoxyb enzenes

On the level of the time-dependent hybrid density functional theory, the one- and two-photon absorption properties of a series of symmetric 4-bis 2-[4-(2-ary12) phenyl]vinyl-2,5-bisdialkoxybenzenes are studied respectively utilizing the analytic response theory and the few-state model methods. The calculated results show that the planarity of the geometrical structure plays a great role in enhancing the linear and nonlinear optical abilities of the molecule. However the effect of the length of the chain linked to the π-centre on the optical property is very little. For the investigated compounds, the A–π–A type charge-transfer molecules display more superior one- and two-photon absorption characteristics than the D–π–D type ones. Furthermore, the two-photon absorption results by use of few-state model are generally consistent with those by analytic response theory, demonstrating the reliability of the few-state model for evaluating the two-photon absorption cross section. The numerical simulations are in good agreement in tendency with the available experimental measurements.     

Strong two-photon absorption at telecommunications wavelengths in nickel bis(dithiolene) complexes

The two-photon absorption spectrum of a nickel bis(dithiolene) complex with extended conjugation and pi-donor substitution is measured by using Z-scan and pump-probe techniques with femtosecond pulses over the spectral range from 1.20 to 1.58 microm, which includes much of the telecommunications range. The peak two-photon cross section of over 5000 GM (1 GM = 10(-50) cm4 s photon(-1) molecule(-1)) occurs at approximately 1.24 microm, with significant two-photon absorption (>440 GM) throughout the spectral range examined.     

Solvent effects on optical properties of a newly synthesized two-photon polymerization initiator： BPYPA

Time-dependent hybrid density functional theory in combination with polarized continuum model is applied to study the solvent effects on the geometrical and electronic structures as well as one- and two-photon absorption processes, of a newly synthesized asymmetrical charge-transfer organic molecule bis-（4-bromo-phenyl）-[4-（2-pyridin-4-yl-vinyl）phenyl]-amine （BPYPA）. There exist two charge-transfer states for the compound in visible region. The two-photon absorption cross section calculated by a three-state model and solvatochromic shift of the charge-transfer states are found to be solvent-dependent, where a nonmonotonic behaviour with respect to the polarity of the solvents is observed. The numerical results show that the organic molecule exhibits a rather large two-photon absorption cross section as compared with the compound 4-trans-[p-（N, N-Di-n-butylamino）-p-stilbenyl vinyl] pyridine （DBASVP） reported previously, and is predicted to be a good two-photon polymerization initiator. The hydrogen-bond effect is analysed. The computational results are in good agreement with the measurements.     

Theoretical studies on the one- and two-photon absorption properties of azulenylporphyrins and azulene-fused porphyrins

The electronic structures, one-photon absorption (OPA) and two-photon absorption (TPA) properties of the azulenylporphyrins and azulene-fused porphyrins have been comparatively studied by using DFT/B3LYP/6-31G(d) and the ZINDO/SDCI method. With the number of azulenyl groups increasing, the OPA wavelengths of all molecules are red-shifted in 400--600~nm and the two-photon absorption cross section is gradually enlarged. The azulene-fused structures facilitate an expanding conjugated area and increasing TPA cross section. The origin of TPA properties of studied compounds is studied with a two-level model. In summary, the azulene-fused porphyrins exhibit strong two-photon absorption.     

二苯乙烯衍生物分子双光子吸收截面：官能团对称性的影响

选取了具有不同对称性的二苯乙烯系列衍生物分子，在HF水平上，利用响应函数方法，研究了该系列分子的单光子和双光子特性. 研究结果表明，该系列分子具有较强的双光子特性. 在可见光范围内，反对称分子的最大双光子吸收态是第一激发态，而对称分子的最大双光子吸收出现在第四激发态. 相对于对称分子而言，反对称分子具有更大的双光子吸收截面. 因此，分子的对称性是否比不对称性更有利于增大分子的双光子吸收截面，还与分子的π中心部分的特性有关. 还给出了电荷转移态的电荷迁移过程. 关键词： 双光子吸收 响应函数方法 非线性光学     

Two-photon induced optical-power limiting and upconverted superradiance properties of a new organic dye HEASPI

A new organic dye trans-4-[p-(N-ethyl-N-hydroxyethylamino)styryl]-N-methylpyridinium iodide (abbreviated as HEASPI hereafter) with large two-photon absorption (TPA) cross section and excellent upconverted superradiance properties was synthesized in our group recently. The TPA cross section was measured to be σ₂′=7.0×10⁻⁴⁸ cm⁴ s/photon by using an open aperture Z-scan system. Linear absorption, single-photon induced fluorescence, two-photon induced fluorescence and two-photon pumped (TPP) upconverted superradiance properties were systematically studied. The highest net upconversion efficiency from the absorbed pump energy to the output upconverted superradiance energy is as high as 19.6% at the pump energy of 2.07 mJ from a mode-locked Nd : YAG picosecond laser. The dye solution also shows a clear optical power limiting effect.