We demonstrate the possibility of controlling the symmetry properties of photoinduced χ<sup>(2)</sup> macroscopic susceptibility in polymer films. Ellipsometric adjustment of the write beams allows one to monitor the macroscopic χ<sup>(2)</sup> symmetry from a dipolar to an octupolar configuration. Experimental results are in agreement with an irreducible spherical tensor-based model jointly applied to the molecular β hyperpolarizability and field tensors. We found a purely octupolar polarization-independent photoinduced second-harmonic-generation response in a Dispersed Red 1–methyl methacrylate thin film. Such a configuration, as generated by an octupolar tensor write field tensor made up of counterclockwise circularly polarized ω and 2ω beams, is not within the reach of the classical electric-field poling technique.
© 1997 Optical Society of America
S. Brasselet and J. Zyss, "Control of the polarization dependence of optically poled nonlinear polymer films," Opt. Lett. 22, 1464-1466 (1997)