The Effect of Matrix Attachment on the Third Order Nonlinear Optical Properties of Dyes
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THE EFFECT OF MATRIX ATTACHMENT ON THE THIRD ORDER NONLINEAR OPTICAL PROPERTIES OF DYES DAVID W. POLlS, MAMOUN M. BADER, AND LARRY R. DALTON Department of Chemistry, University of Southern California, Los Angeles, CA 90089-0482
ABSTRACT In order to discern the source of the third order nonlinear optical (NLO) phenomenon both morphological and electronic considerations are required. A series of styrene copolymers with varying amounts of p-aminostyrene or pchloromethylstyrene were prepared as anchoring sites for chemically reactive electrophilic and nucleophilic dyes. For comparison, the same dyes were incorporated into composites of polycarbonate. Preliminary degenerate four wave mixing results for all materials indicate that the copolymeric support allowed incorporation of greater amounts of electroactive units, versus 3 composites, and hence allowed high third order nonlinear responses (X()/hx of approximately 10-13 esu cm). Third order NLO responses were absent in some composite systems due to limited solubility and/or phase separation difficulties.
INTRODUCTION Rigid rod ladder polymers and their third order NLO properties have been extensively studied [1]. Also, NLO properties of ladder oligomer units incorporated into polyethers with large spacer groups have been investigated in attempts to minimize absorption and solubility problems associated with the rigid rod systems [2]. These studies have raised questions as to what the morphological dependence is on the NLO phenomenon. There have been many examples of composites incorporating electroactive units exhibiting second and third order NLO properties [3]. Also, it has been established that polymers with long pendant groups incorporating a electroactive unit can display liquid crystalline behavior and can be poled to yield materials with enhanced second order NLO properties [4]. This is a clear indication of morphological dependencies on the second order NLO effect. We are interested in understanding whether polymers with pendant electroactive groups attached close to the polymer chain display third order NLO behavior and whether this behavior is enhanced incomparison to randomly distributed molecules in composite films. This study utilized both electrophilic and nucleophilic polymers to facilitate attachment of a wide variety of electrophilic and nucleophilic dyes possessing chemically reactive amino, or halo substituents. Initial NLO results for incorporated and composite materials of 7-nitrobenzo-2-oxa-l,3-diazole (E1, Figure 1) will be discussed. Also, limitations to both procedures for dye incorporation will be addressed. Mat. Res. Soc. Symp. Proc. Vol. 173. ©1990 Materials Research Society
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