The study result indicate that , the asymmetry substituted molecules display larger two - photon absorption cross sections than the symmetry substituted molecules , which illustrates that the effect of the different substitutions on molecule ' s two - photon absorption property is related to the property of molecule ' s - center 98程序包上完成。结果表明在此五种化合物中具有不对称结构的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。
The molecules we studied are a series of trans - stilbene derivatives . first , we applied dft method optimized the new synthesis molecule 4 , 4 ' - bis ( dimethylamino ) stilbene ' s structure , and used few states model calculated its tpa cross section . the results agree well with the experiment data 首先，我们在密度泛函理论( densityfunctiontheory )的水平上对最近合成的分子材料4 ， 4 -二甲氨基二苯乙烯的结构进行了优化，然后采用少态模型方法计算了分子的双光子吸收截面，得到了与实验符合很好的结果。
We have calculated one - and two - photon absorption cross sections of the lowest excited states of a series of molecules combined with benzene , stilben , thiophene as center attached with amine , diphenylamine , diethylamine as electron - donor and nitryl as electron - acceptor ; the effects of molecular length , n center and electron - donor on two - photon absorption cross sections have been studied and all calculations have been carried out using the density functional theory at an ab initio level . it is found that the molecular length and the one - photon absorption intensity are quite strongly c orrelated factors , and that a corresponding correlation for the two - photon absorption is decreasing . it is also found that a most crucial role for the two - photon absorption is played by the n center 我们分别以苯、二苯乙烯、噻吩为中心，氨基、二苯氨基和二乙氨基为电子给体，硝基为电子受体组合形成的分子为研究对象，在从头计算的水平上用密度泛函理论计算了这些分子在低激发态下的单、双光子吸收强度，重点研究了分子的长度、中心和给体的供电子能力对分子单、双光子吸收的影响。研究结果表明，分子长度与单光子吸收强度之间有密切关系，而在双光子吸收中这种关系较弱；中心在双光子吸收中具有重要的作用；在中心和受体一定的情况下，增加给体的供电子能力，可提高双光子吸收强度。
Such measares as elecbe spetri , fluorescence spectruin in solution and in solid , two - photon absorphon , ophcal lindting are employed in these studies . we find that all of these compounds have ligh - excited emitting properies and non - linear absorphon properties at different extents . all of this properties lay out applied prospects of them in opt - eiectron funchonal materials area 分为电子光谱，液体荧光，固体荧光，双光子吸收，光限幅和z扫描研究，发现产物都有光致发光性质，并有不同程度的非线性吸收性质，展示了其在光学材料领域的应用前景。
We analyze the influences of the perturbed energy - level space and superposion , laser power and intermediate level offset on quantum interference . experimentally , in the sodium dimmer rhomb - type four - level system with a pair of perturbed levels , the interference enhancement of two - photon absorption caused by coherent superposition of the perturbed levels is experimentally observed 分析了微扰能级的间隔和叠加程度、激光功率以及中间能级的失谐对量子干涉效应的影响，实验上观察了包含有一对微扰叠加中间能级的菱形四能级系统中的双光子激发现象，发现微扰能级的相干叠加可增强双光子吸收。
On theoretical , a diffraction model of a nonlinear optical medium to a gaussian beam was built based on fresnel - kirchhoff diffraction theory . the propagation behavior of the gaussian beam passing through the nonlinear optical medium was theoretically deduced and numerically simulated , which could explain the z - scan phenomenon from a new approach . it provides a new way to calculate the nonlinear refraction index and the two - photon absorption coefficients 理论方面，以菲涅尔?基尔霍夫衍射理论为基础，建立了非线性介质对高斯光束的衍射模型，对高斯光束通过非线性介质后的传输行为进行了详细的理论推导和数值计算，从一种新的角度解释了z -扫描现象，是计算非线性折射率和双光子吸收系数的一种新方法。
Materials with strong two - photon absorption ( tpa ) are currently attracting considerable attention in the chemistry , photonics and biology communities because of their potential applications in optical power limiting , upconverted lasering , three - dimensional datastorage , nondestructiveimaging and photodynamic therapy 强双光子吸收材料由于在激光限幅、双光子上转换激射、三维信息存储、生物体三维成像、光动力学治癌等方面具有诱人的应用前景，成为材料化学、光子学、生物学等领域的关注热点。
The linear and nonlinear optical properties of these compounds have been systematically studied . the following parts are included in this thesis : one - photon and two - photon fluorescence ; upconversion superradiance and cavity lasing properties ; the optical power limiting effect of these compounds ; and so on . tpa absorption coefficients have been got by z - scan method 3 、系统研究了它们的线性和非线性光学性质，主要包括：单、双光子荧光，上转换超辐射和腔激射性能及其效率，光限幅效应，用z - scan的方法得到了其双光子吸收截面。
