Second Order Nonlinear Optical Properties of Polymers Containing Mesogenic Side Chains

Abstract

Abstract Second harmonic generation is observed from poled polymer films which contain a side chain mesogen with nonlinear optical (NLO) properties. The side chain is a derivative of 4-hydroxy-4′-nitrostilbene (HNS), and the content is varied by copolymerization with methyl methacrylate. The polymer exhibits a liquid crystalline (LC) phase when the side chain content is greater than 75 mol%. LC orientation is induced by poling for the homopolymer. The second order NLO susceptibility (χ(2)) of the oriented homopolymer is 1.5 times larger than the estimated value when the polymer is isotropic under the same poling field. This enhancement corresponds to the large anisotropic properties of the polymer. By doping HNS to the homopolymer, the χ(2) value increases with increases in the doping content up to 20 mol% where the LC orientation remains, and reaches 1.6 times the value of the undoped homopolymer.