Second Harmonic Generation by Polymer Composites

Abstract

ABSTRACTSecond harmonic generation was observed from composites consisting of 3-nitroaniline or 3-methyl-4-nitroaniline grown within a polymer matrix. In the amorphous polymers, polystyrene and poly(methyl methacrylate), the crystals formed as fine grains or needles. The intensity of the second harmonic, from Nd-YAG light at 1.06 μm, was measured as a function of the composition from 10–90 wt% of nitroaniline. The angular distribution of the light output was very dependent on the morphology of the precipitate, with a strong concentration of the output in the forward direction for samples containing locally aligned, needle-like crystals. The behaviour in SHG and in light scattering was compared.Composites with crystalline polymers were prepared as unoriented or oriented films. Nitroanilines and potassiun dihydrogen orthophosphate were crystallised from a number of polymers. The composite structure is governed particularly by the extent of liquid phase miscibility. The potential for optical applications of these materials are discussed.