Second-Order Nonlinear Optical Properties of Highly Symmetric Chiral Thin Films

We demonstrate second-harmonic generation in highly symmetric thin films of chiral molecules. The films were prepared by spin-coating, and no external force (such as electric field poling) was used to induce noncentrosymmetry. The films have a nonpolar D n symmetry with second-order susceptibility values of 2−9 pm/V. Furthermore, the samples are stable at elevated temperatures.