High nonlinear optical anisotropy of urea nanofibers

Nanofibers consisting of the optically nonlinear organic molecule urea embedded in both poly(ethylene oxide) (PEO) and poly(vinyl alcohol) (PVA) polymers were produced by the electrospinning technique. The second-harmonic generation produced by aligned fiber mats of these materials displays a strong dependence on the polarization of the incident light. In PVA-urea nanofibers the effectiveness in generating of the second-harmonic light is as high as that of a pure urea powder with an average grain size of 110 μm. The results suggest that single crystalline urea nanofibers were achieved with a long-range crystalline order extending into the range of 2–4 μm with PVA as the host polymer.This work was carried out in the frame of CIENCIA-2007 program (reference UMINHO-CF06) and financially supported by Fundacao para a Ciencia e Tecnologia, PTDC/CTM/105597/2008