Three-Coupled-Oscillator Model Of Optical Nonlinearty Of Chiral Molecular Medium

In this dissertation, the research progress of nonlinear optics in chiral molecules and chiral molecular media is reviewed, the development tendency and potential applications are pointed out, and the importance of studying the chirality by means of nonlinear optical techniques is emphasized. The classical molecular models are very effective to explain the nonlinear optical properties of chiral molecular system. The classical theory can give us clear physical picture and bring us instructive information about the link between the molecular configuration and the nonlinear processes.In this dissertation, a new nonlinear microscopic model of chiral molecules, the three-coupled-oscillator models is developed from the well known classical models of chiral molecules for the first time to our knowledge. The model is suitable for chiral molecules with the tripod-like structure. The polarization mechanism of chiral molecule with tripod-like structure is presented by using the new three-coupled-oscillator model, and the microscopic polarizabilities, include the linear and the second-order nonlinear polarizabilities (namely hyperpolarizabilityβ) of chiral molecules with tripod-like structure is deduced. The applicability and validity of this new three-coupled-oscillator model is verified by the calculation results of hyperpolarizabilitiesβin NPAN molecules, which are in good agreement with the experimental results in the literatures. The relation between molecular polarization and medium polarization isinvestigated, and general expression of molecular susceptibilities and medium susceptibilities is obtained taking the local-field effect and the nonlocal-field effects into account, respectively. The relative formula between susceptibilities of thin-film media and hyperpolarizabilities of chiral molecules is deduced from the statistical average theory.The surface second harmonic generation (SHG) process of chiral thin-film...