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Prediction of nonlinear optical properties of organic materials. General theoretical considerationsThe prediction of nonlinear optical properties of organic materials is geared to assist materials scientists in the selection of good candidate molecules. A brief summary of the quantum mechanical methods used for estimating hyperpolarizabilities will be presented. The advantages and limitations of each technique will be discussed. Particular attention will be given to the finite-field method for calculating first and second order hyperpolarizabilities, since this method is better suited for large molecules. Corrections for dynamic fields and bulk effects will be discussed in detail, focusing on solvent effects, conformational isomerization, core effects, dispersion, and hydrogen bonding. Several results will be compared with data obtained from third-harmonic-generation (THG) and dc-induced second harmonic generation (EFISH) measurements. These comparisons will demonstrate the qualitative ability of the method to predict the relative strengths of hyperpolarizabilities of a class of compounds. The future application of molecular mechanics, as well as other techniques, in the study of bulk properties and solid state defects will be addressed. The relationship between large values for nonlinear optical properties and large conjugation lengths is well known, and is particularly important for third-order processes. For this reason, the materials with the largest observed nonresonant third-order properties are conjugated polymers. An example of this type of polymer is polydiacetylene. One of the problems in dealing with polydiacetylene is that substituents which may enhance its nonlinear properties may ultimately prevent it from polymerizing. A model which attempts to predict the likelihood of solid-state polymerization is considered, along with the implications of the assumptions that are used. Calculations of the third-order optical properties and their relationship to first-order properties and energy gaps will be discussed. The relationship between monomeric and polymeric third-order optical properties will also be considered.
Document ID
19940019870
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Cardelino, B.
(Atlanta Univ. Center Inc., GA., United States)
Moore, C.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Zutaut, S.
(Alabama Univ. Huntsville., United States)
Date Acquired
September 6, 2013
Publication Date
December 1, 1993
Publication Information
Publication: Microgravity Studies of Organic and Polymeric Materials
Subject Category
Optics
Accession Number
94N24343
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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