Poled Polymeric Second Harmonic Generation Materials. Chemical Manipulation of the Temporal Characteristics of Electric Field-Induced Noncentrosymmetry

摘要

This contribution describes two approaches to the construction of polymeric nonlinear optical materials with persistent second harmonic generation efficiency. In the first, poly(p-hydroxystyrene) is covalently functionalized with chromophores having large quadratic hyperpolarizabilities. Films of these polymers are poled at fields up to 1.8 MV/cm to yield materials with stable (on the timescale of months) second harmonic coefficients (d33) as high as 18 x 10 to the-9 power esu. In site measurements indicate that field-induced chromophore alignment is rapid at temperature substantially below T sub g and that relaxation of the alignment is even more rapid upon removal of the field. Annealing of the films prior to poling enhances the stability of second harmonic generation and allows poling at higher fields. A second approach is disperse chromophores in an uncured epoxy host and to then simultaneously cure and pole the resulting ensembles. This procedure also stabilizes preferential chromophore alignments for relatively long periods of time. Reprints. (AW)