The Protonation Effcet On Two Photon Absorption Properties Of The Molecule

The birth of laser promotes the rapid development of non-linear optical and makes it one ofimportant modern optics branch. Nonlinear optics has attracted much people s attention. In recentyears, due to the nolinear optical materials widely used in laser frequency doubling, laserfrequency mixing, parametric amplification and oscillation, integrated optics, opticalcommunication, beam steering, beam distortion removing, image multiplication andtransformation, optical limiting and threshold monitoring, complete optical connecting, opticalcomputer and other fields and showing attractive application foreground are deserved for peopleto study. Meanwhile, Much emphasis has been put on organic nonlinear optical materialsbecause they have many advantages which inorganic materials can t pursue, such as wideresponse wave band, high optical damage threshold, well flexibility, low cost and easycombination and modification. Recently, the two photon sensor are used in biological whichdraw many researcher’s attention and PH seneor based on two photon fluorescence are alsopopular study object.The thesis studies the linear and nonlinear optical properties of a series of organic moleculesutilizing modern quantum chemical calculation theory.The solvent effect is also considered. Thewhole works contain two parts: one part is the study of the protonation effect on one-andtwo-photon absorption (OPA and TPA) properties of4-N,N-dimethylamino-4-amino-azobenzene.The other part is about the cooperative branch effect on two-photon absorption properties oftriphenylamine derivatives. The main contents and results are represented as follows.1. the protonation effect on one-and two-photon absorption of azobenzene derivatives.The protonation effect on one-and two-photon absorption (TPA) properties of4-N,N-dimethylamino-4-amino-azobenzene has been theoretically investigated at DFT level. Thecalculated results show that the dominated one photon absorption (OPA) wavelength of the protonated conformers are shifted in various degrees compared with the neutral form. The largestTPA cross sections of all the protonated form show consistent decreasing tendency due to theprotonation effect weakening the electron donating strength of the substitute. The studiedconfigurations with symmetric functional group have larger TPA cross section than that withasymmetric functional group. Besides, the long rang interaction effect simulated by the polarizedcontinuum model is also proved to have great impact on both OPA and TPA properties.2. the cooperative branch effect on two-photon absorption properties of triphenylaminederivatives.The one-and two-photon absorption properties of triphenylamine derivatives have beeninvestigated at density function theory (DFT) level. The numerical results indicate that theone-photon absorption intensities are strengthened and the corresponding wavelength shows ared shift with the increasing number of the arms for the derivatives. The two-photon absorptioncross-sections are also largely enhanced. The cooperative branch effect is contributed to enhancethe optical properties of the molecules. The theoretical results give a good explanation for theexperimental observation.The content of this thesis is as follows. There are six chapters.The first chapter gives a briefintroduction of nonlinear optics and also the developing process of nonlinear optical materials. Inthe second chapter, some quantum chemistry theories of studying the nonlinear properties areintroduced, including the the Hartree-Fock approximation and the density functional theory. Inthe third chapter, the different approaches developed recently for calculating moleculartwo-photon absorption properties are summarized, including sum-over-state, few-statemodel,finite field and response theory methods. The protonation effect on photon absorptionproperties are discussed in the forth chapter; In the fifth chapter, we show the the cooperativebranch effect on two-photon absorption properties of triphenylamine derivatives In the lastchapter, the summary and the prospect are represented.