Depth-resolved imaging of nematic liquid crystals by third-harmonic microscopy

Third-harmonic microscopy is shown to be a powerful tool for the study of l iquid crystal structures. The third-harmonic probe enables the investigatio n of molecular order well inside a liquid crystal cell. The observation of phase transition in various nematic liquid crystal samples is presented as a demonstration for the power of this technique. For example, nematic and i sotropic regions are shown to coexist across the depth of the cell. Thermal fluctuations are observed in the nematic regions close to the isotropic-ne matic transition temperature. (C) 1999 American Institute of Physics. [S000 3-6951(99)04321-1].