A Folded Mainchain NLO Polymer: Optical Properties and Poling Stability

Nonlinear optical (NLO) organic molecules (chromophores) incorporated into polymers have attracted considerable interest1 for photonics applications due to their fast NLO response time, low cost, ease of fabrication, and large nonlinear second-order electric susceptibility, χ(2). One focus of current research is the enhancement of the thermal and temporal stability of χ(2), which in NLO polymers is dependent on the stability of the Chromophore orientation. This orientation, necessary for the removal of inversion symmetry in order to obtain a nonzero χ(2), can be achieved by electric field poling.2,3 The field is applied at temperatures near or above the glass transition temperature to orient the chromophores and removed only after cooling down to near room temperature. The stability of the resulting order in the thermodynamic nonequilibrium glassy state varies from polymer to polymer. Chemical attachment of the Chromophore to the polymer — as a sidechain,4-6 as part of the main chain,7,8 or in a crosslinked structure8-10 — has been found to retard the relaxation of orientational order.